Merge pull request #7480 from gamebox/new-pnc-expr-node

Move PNC apply to separate Expr/Pattern variant

crates/compiler/builtins/roc/Dict.roc

@@ -133,8 +133,10 @@ hash_dict = \hasher, dict -> Hash.hash_unordered(hasher, to_list(dict), List.wal
 
 to_inspector_dict : Dict k v -> Inspector f where k implements Inspect & Hash & Eq, v implements Inspect, f implements InspectFormatter
 to_inspector_dict = \dict ->
-    Inspect.custom(\fmt ->
+    Inspect.custom(
-        Inspect.apply(Inspect.dict(dict, walk, Inspect.to_inspector, Inspect.to_inspector), fmt))
+        \fmt ->
+            Inspect.apply(Inspect.dict(dict, walk, Inspect.to_inspector, Inspect.to_inspector), fmt),
+    )
 
 ## Return an empty dictionary.
 ## ```roc
@@ -142,13 +144,15 @@ to_inspector_dict = \dict ->
 ## ```
 empty : {} -> Dict * *
 empty = \{} ->
-    @Dict({
+    @Dict(
+        {
             buckets: [],
             data: [],
             max_bucket_capacity: 0,
             max_load_factor: default_max_load_factor,
             shifts: initial_shifts,
-    })
+        },
+    )
 
 ## Return a dictionary with space allocated for a number of entries. This
 ## may provide a performance optimization if you know how many entries will be
@@ -169,13 +173,15 @@ reserve = \@Dict({ buckets, data, max_bucket_capacity: original_max_bucket_capac
     if List.is_empty(buckets) || requested_shifts > shifts then
         (buckets0, max_bucket_capacity) = alloc_buckets_from_shift(requested_shifts, max_load_factor)
         buckets1 = fill_buckets_from_data(buckets0, data, requested_shifts)
-        @Dict({
+        @Dict(
+            {
                 buckets: buckets1,
                 data: List.reserve(data, Num.sub_saturated(size, current_size)),
                 max_bucket_capacity,
                 max_load_factor,
                 shifts: requested_shifts,
-        })
+            },
+        )
     else
         @Dict({ buckets, data, max_bucket_capacity: original_max_bucket_capacity, max_load_factor, shifts })
 
@@ -191,13 +197,15 @@ release_excess_capacity = \@Dict({ buckets, data, max_bucket_capacity: original_
     if min_shifts < shifts then
         (buckets0, max_bucket_capacity) = alloc_buckets_from_shift(min_shifts, max_load_factor)
         buckets1 = fill_buckets_from_data(buckets0, data, min_shifts)
-        @Dict({
+        @Dict(
+            {
                 buckets: buckets1,
                 data: List.release_excess_capacity(data),
                 max_bucket_capacity,
                 max_load_factor,
                 shifts: min_shifts,
-        })
+            },
+        )
     else
         @Dict({ buckets, data, max_bucket_capacity: original_max_bucket_capacity, max_load_factor, shifts })
 
@@ -280,14 +288,16 @@ is_empty = \@Dict({ data }) ->
 ## ```
 clear : Dict k v -> Dict k v
 clear = \@Dict({ buckets, data, max_bucket_capacity, max_load_factor, shifts }) ->
-    @Dict({
+    @Dict(
+        {
             buckets: List.map(buckets, \_ -> empty_bucket),
             # use take_first to keep around the capacity
             data: List.take_first(data, 0),
             max_bucket_capacity,
             max_load_factor,
             shifts,
-    })
+        },
+    )
 
 ## Convert each value in the dictionary to something new, by calling a conversion
 ## function on each of them which receives both the key and the old value. Then return a
@@ -822,21 +832,25 @@ remove_bucket = \@Dict({ buckets: buckets0, data: data0, max_bucket_capacity, ma
         bucket_index3 = scan_for_index(buckets2, bucket_index2, Num.to_u32(last_data_index))
         swap_bucket = list_get_unsafe(buckets2, bucket_index3)
 
-        @Dict({
+        @Dict(
+            {
                 buckets: List.set(buckets2, bucket_index3, { swap_bucket & data_index: data_index_to_remove }),
                 data: List.drop_last(data1, 1),
                 max_bucket_capacity,
                 max_load_factor,
                 shifts,
-        })
+            },
+        )
     else
-        @Dict({
+        @Dict(
+            {
                 buckets: buckets2,
                 data: List.drop_last(data0, 1),
                 max_bucket_capacity,
                 max_load_factor,
                 shifts,
-        })
+            },
+        )
 
 scan_for_index : List Bucket, U64, U32 -> U64
 scan_for_index = \buckets, bucket_index, data_index ->
@@ -863,13 +877,15 @@ increase_size = \@Dict({ data, max_bucket_capacity, max_load_factor, shifts }) -
         new_shifts = shifts |> Num.sub_wrap(1)
         (buckets0, new_max_bucket_capacity) = alloc_buckets_from_shift(new_shifts, max_load_factor)
         buckets1 = fill_buckets_from_data(buckets0, data, new_shifts)
-        @Dict({
+        @Dict(
+            {
                 buckets: buckets1,
                 data,
                 max_bucket_capacity: new_max_bucket_capacity,
                 max_load_factor,
                 shifts: new_shifts,
-        })
+            },
+        )
     else
         crash("Dict hit limit of $(Num.to_str(max_bucket_count)) elements. Unable to grow more.")
 

crates/compiler/builtins/roc/List.roc

@@ -1092,11 +1092,15 @@ min = \list ->
 
 min_help : List (Num a), Num a -> Num a
 min_help = \list, initial ->
-    List.walk(list, initial, \best_so_far, current ->
+    List.walk(
+        list,
+        initial,
+        \best_so_far, current ->
             if current < best_so_far then
                 current
             else
-            best_so_far)
+                best_so_far,
+    )
 
 max : List (Num a) -> Result (Num a) [ListWasEmpty]
 max = \list ->
@@ -1109,11 +1113,15 @@ max = \list ->
 
 max_help : List (Num a), Num a -> Num a
 max_help = \list, initial ->
-    List.walk(list, initial, \best_so_far, current ->
+    List.walk(
+        list,
+        initial,
+        \best_so_far, current ->
             if current > best_so_far then
                 current
             else
-            best_so_far)
+                best_so_far,
+    )
 
 ## Like [List.map], except the transformation function wraps the return value
 ## in a list. At the end, all the lists get joined together into one list.
@@ -1156,11 +1164,15 @@ find_last = \list, pred ->
 ## If no satisfying element is found, an `Err NotFound` is returned.
 find_first_index : List elem, (elem -> Bool) -> Result U64 [NotFound]
 find_first_index = \list, matcher ->
-    found_index = List.iterate(list, 0, \index, elem ->
+    found_index = List.iterate(
+        list,
+        0,
+        \index, elem ->
             if matcher(elem) then
                 Break(index)
             else
-            Continue(Num.add_wrap(index, 1)))
+                Continue(Num.add_wrap(index, 1)),
+    )
 
     when found_index is
         Break(index) -> Ok(index)
@@ -1171,13 +1183,17 @@ find_first_index = \list, matcher ->
 ## If no satisfying element is found, an `Err NotFound` is returned.
 find_last_index : List elem, (elem -> Bool) -> Result U64 [NotFound]
 find_last_index = \list, matches ->
-    found_index = List.iterate_backwards(list, List.len(list), \prev_index, elem ->
+    found_index = List.iterate_backwards(
+        list,
+        List.len(list),
+        \prev_index, elem ->
             answer = Num.sub_wrap(prev_index, 1)
 
             if matches(elem) then
                 Break(answer)
             else
-            Continue(answer))
+                Continue(answer),
+    )
 
     when found_index is
         Break(index) -> Ok(index)
@@ -1214,10 +1230,14 @@ intersperse = \list, sep ->
     capacity = 2 * List.len(list)
     init = List.with_capacity(capacity)
     new_list =
-        List.walk(list, init, \acc, elem ->
+        List.walk(
+            list,
+            init,
+            \acc, elem ->
                 acc
                 |> List.append_unsafe(elem)
-            |> List.append_unsafe(sep))
+                |> List.append_unsafe(sep),
+        )
 
     List.drop_last(new_list, 1)
 
@@ -1359,9 +1379,16 @@ chunks_of_help = \list_rest, chunk_size, chunks ->
 ## If it returns `Ok` for every element, [map_try] returns `Ok` with the transformed list.
 map_try : List elem, (elem -> Result ok err) -> Result (List ok) err
 map_try = \list, to_result ->
-    walk_try(list, [], \state, elem ->
+    walk_try(
-        Result.map(to_result(elem), \ok ->
+        list,
-            List.append(state, ok)))
+        [],
+        \state, elem ->
+            Result.map(
+                to_result(elem),
+                \ok ->
+                    List.append(state, ok),
+            ),
+    )
 
 ## Same as [List.walk], except you can stop walking early by returning `Err`.
 ##

crates/compiler/builtins/roc/Set.roc

@@ -51,19 +51,25 @@ is_eq = \xs, ys ->
     if len(xs) != len(ys) then
         Bool.false
     else
-        walk_until(xs, Bool.true, \_, elem ->
+        walk_until(
+            xs,
+            Bool.true,
+            \_, elem ->
                 if contains(ys, elem) then
                     Continue(Bool.true)
                 else
-                Break(Bool.false))
+                    Break(Bool.false),
+        )
 
 hash_set : hasher, Set k -> hasher where hasher implements Hasher
 hash_set = \hasher, @Set(inner) -> Hash.hash(hasher, inner)
 
 to_inspector_set : Set k -> Inspector f where k implements Inspect & Hash & Eq, f implements InspectFormatter
 to_inspector_set = \set ->
-    Inspect.custom(\fmt ->
+    Inspect.custom(
-        Inspect.apply(Inspect.set(set, walk, Inspect.to_inspector), fmt))
+        \fmt ->
+            Inspect.apply(Inspect.set(set, walk, Inspect.to_inspector), fmt),
+    )
 
 ## Creates a new empty `Set`.
 ## ```roc
@@ -326,8 +332,12 @@ map : Set a, (a -> b) -> Set b
 map = \set, transform ->
     init = with_capacity(capacity(set))
 
-    walk(set, init, \answer, k ->
+    walk(
-        insert(answer, transform(k)))
+        set,
+        init,
+        \answer, k ->
+            insert(answer, transform(k)),
+    )
 
 ## Like [Set.map], except the transformation function wraps the return value
 ## in a set. At the end, all the sets get joined together
@@ -338,8 +348,12 @@ join_map : Set a, (a -> Set b) -> Set b
 join_map = \set, transform ->
     init = with_capacity(capacity(set)) # Might be a pessimization
 
-    walk(set, init, \answer, k ->
+    walk(
-        union(answer, transform(k)))
+        set,
+        init,
+        \answer, k ->
+            union(answer, transform(k)),
+    )
 
 ## Iterate through the values of a given `Set` and build a value, can stop
 ## iterating part way through the collection.

crates/compiler/builtins/roc/Str.roc

@@ -940,14 +940,16 @@ matches_at = \haystack, haystack_index, needle ->
     needle_length = Str.count_utf8_bytes(needle)
     end_index = min(Num.add_saturated(haystack_index, needle_length), haystack_length)
 
-    matches_at_help({
+    matches_at_help(
+        {
             haystack,
             haystack_index,
             needle,
             needle_index: 0,
             needle_length,
             end_index,
-    })
+        },
+    )
 
 matches_at_help = \state ->
     { haystack, haystack_index, needle, needle_index, needle_length, end_index } = state

crates/compiler/builtins/roc/Task.roc

@@ -108,10 +108,12 @@ err = \a -> @Task(\{} -> Err(a))
 ## matching to handle the success and possible failure cases.
 attempt : Task a b, (Result a b -> Task c d) -> Task c d
 attempt = \@Task(task), transform ->
-    @Task(\{} ->
+    @Task(
+        \{} ->
             @Task(transformed) = transform(task({}))
 
-        transformed({}))
+            transformed({}),
+    )
 
 ## Take the success value from a given [Task] and use that to generate a new [Task].
 ##
@@ -131,14 +133,16 @@ attempt = \@Task(task), transform ->
 ## ```
 await : Task a b, (a -> Task c b) -> Task c b
 await = \@Task(task), transform ->
-    @Task(\{} ->
+    @Task(
+        \{} ->
             when task({}) is
                 Ok(a) ->
                     @Task(transformed) = transform(a)
                     transformed({})
 
                 Err(b) ->
-                Err(b))
+                    Err(b),
+    )
 
 ## Take the error value from a given [Task] and use that to generate a new [Task].
 ##
@@ -149,14 +153,16 @@ await = \@Task(task), transform ->
 ## ```
 on_err : Task a b, (b -> Task a c) -> Task a c
 on_err = \@Task(task), transform ->
-    @Task(\{} ->
+    @Task(
+        \{} ->
             when task({}) is
                 Ok(a) ->
                     Ok(a)
 
                 Err(b) ->
                     @Task(transformed) = transform(b)
-                transformed({}))
+                    transformed({}),
+    )
 
 ## Transform the success value of a given [Task] with a given function.
 ##
@@ -167,10 +173,12 @@ on_err = \@Task(task), transform ->
 ## ```
 map : Task a c, (a -> b) -> Task b c
 map = \@Task(task), transform ->
-    @Task(\{} ->
+    @Task(
+        \{} ->
             when task({}) is
                 Ok(a) -> Ok(transform(a))
-            Err(b) -> Err(b))
+                Err(b) -> Err(b),
+    )
 
 ## Transform the error value of a given [Task] with a given function.
 ##
@@ -181,10 +189,12 @@ map = \@Task(task), transform ->
 ## ```
 map_err : Task c a, (a -> b) -> Task c b
 map_err = \@Task(task), transform ->
-    @Task(\{} ->
+    @Task(
+        \{} ->
             when task({}) is
                 Ok(a) -> Ok(a)
-            Err(b) -> Err(transform(b)))
+                Err(b) -> Err(transform(b)),
+    )
 
 ## Use a Result among other Tasks by converting it into a [Task].
 from_result : Result a b -> Task a b
@@ -197,8 +207,11 @@ from_result = \res ->
 batch : Task a c -> (Task (a -> b) c -> Task b c)
 batch = \current ->
     \next ->
-        await(next, \f ->
+        await(
-            map(current, f))
+            next,
+            \f ->
+                map(current, f),
+        )
 
 ## Combine the values of two tasks with a custom combining function.
 ##
@@ -214,11 +227,13 @@ batch = \current ->
 ## ```
 combine : Task a err, Task b err, (a, b -> c) -> Task c err
 combine = \@Task(left_task), @Task(right_task), combiner ->
-    @Task(\{} ->
+    @Task(
+        \{} ->
             left = try(left_task, {})
             right = try(right_task, {})
 
-        Ok(combiner(left, right)))
+            Ok(combiner(left, right)),
+    )
 
 ## Apply each task in a list sequentially, and return a list of the resulting values.
 ## Each task will be awaited before beginning the next task.
@@ -232,14 +247,20 @@ combine = \@Task(left_task), @Task(right_task), combiner ->
 ##
 sequence : List (Task ok err) -> Task (List ok) err
 sequence = \task_list ->
-    Task.loop((task_list, List.with_capacity(List.len(task_list))), \(tasks, values) ->
+    Task.loop(
+        (task_list, List.with_capacity(List.len(task_list))),
+        \(tasks, values) ->
             when tasks is
                 [task, .. as rest] ->
-                Task.map(task, \value ->
+                    Task.map(
-                    Step((rest, List.append(values, value))))
+                        task,
+                        \value ->
+                            Step((rest, List.append(values, value))),
+                    )
 
                 [] ->
-                Task.ok(Done(values)))
+                    Task.ok(Done(values)),
+    )
 
 ## Apply a task repeatedly for each item in a list
 ##
@@ -253,8 +274,12 @@ sequence = \task_list ->
 ##
 for_each : List a, (a -> Task {} b) -> Task {} b
 for_each = \items, fn ->
-    List.walk(items, ok({}), \state, item ->
+    List.walk(
-        state |> await(\_ -> fn(item)))
+        items,
+        ok({}),
+        \state, item ->
+            state |> await(\_ -> fn(item)),
+    )
 
 ## Transform a task that can either succeed with `ok`, or fail with `err`, into
 ## a task that succeeds with `Result ok err`.
@@ -274,5 +299,7 @@ for_each = \items, fn ->
 ##
 result : Task ok err -> Task (Result ok err) *
 result = \@Task(task) ->
-    @Task(\{} ->
+    @Task(
-        Ok(task({})))
+        \{} ->
+            Ok(task({})),
+    )

crates/compiler/can/src/derive.rs

@@ -8,7 +8,7 @@
 
 use roc_error_macros::internal_error;
 use roc_module::{called_via::CalledVia, symbol::Symbol};
-use roc_parse::ast::{self, Collection, PatternApplyStyle};
+use roc_parse::ast::{self, Collection};
 use roc_region::all::{Loc, Region};
 
 use crate::{env::Env, pattern::Pattern, scope::Scope};
@@ -27,7 +27,6 @@ fn to_encoder<'a>(env: &mut Env<'a>, at_opaque: &'a str) -> ast::Expr<'a> {
             DERIVED_REGION,
             ast::Pattern::Identifier { ident: payload },
         )]),
-        ast::PatternApplyStyle::Whitespace,
     );
 
     // Encode.to_encoder(payload)
@@ -40,7 +39,7 @@ fn to_encoder<'a>(env: &mut Env<'a>, at_opaque: &'a str) -> ast::Expr<'a> {
             module_name: "",
             ident: payload,
         })]),
-        roc_module::called_via::CalledVia::Space,
+        CalledVia::Space,
     ));
 
     // \@Opaq payload -> Encode.to_encoder(payload)
@@ -133,7 +132,6 @@ fn hash<'a>(env: &mut Env<'a>, at_opaque: &'a str) -> ast::Expr<'a> {
             DERIVED_REGION,
             ast::Pattern::Identifier { ident: payload },
         )]),
-        PatternApplyStyle::Whitespace,
     );
 
     // Hash.hash(hasher, payload)
@@ -152,7 +150,7 @@ fn hash<'a>(env: &mut Env<'a>, at_opaque: &'a str) -> ast::Expr<'a> {
                 ident: payload,
             }),
         ]),
-        roc_module::called_via::CalledVia::Space,
+        CalledVia::Space,
     ));
 
     // \hasher, @Opaq payload -> Hash.hash(hasher, payload)
@@ -180,7 +178,6 @@ fn is_eq<'a>(env: &mut Env<'a>, at_opaque: &'a str) -> ast::Expr<'a> {
             DERIVED_REGION,
             ast::Pattern::Identifier { ident: payload1 },
         )]),
-        PatternApplyStyle::Whitespace,
     );
     // \@Opaq payload2
     let opaque2 = ast::Pattern::Apply(
@@ -189,7 +186,6 @@ fn is_eq<'a>(env: &mut Env<'a>, at_opaque: &'a str) -> ast::Expr<'a> {
             DERIVED_REGION,
             ast::Pattern::Identifier { ident: payload2 },
         )]),
-        PatternApplyStyle::Whitespace,
     );
 
     // Bool.is_eq(payload1, payload2)
@@ -208,7 +204,7 @@ fn is_eq<'a>(env: &mut Env<'a>, at_opaque: &'a str) -> ast::Expr<'a> {
                 ident: payload2,
             }),
         ]),
-        roc_module::called_via::CalledVia::Space,
+        CalledVia::Space,
     ));
 
     // \@Opaq payload1, @Opaq payload2 -> Bool.is_eq(payload1, payload2)
@@ -236,7 +232,6 @@ fn to_inspector<'a>(env: &mut Env<'a>, at_opaque: &'a str) -> ast::Expr<'a> {
             DERIVED_REGION,
             ast::Pattern::Identifier { ident: payload },
         )]),
-        PatternApplyStyle::Whitespace,
     );
 
     // Inspect.to_inspector(payload)
@@ -249,7 +244,7 @@ fn to_inspector<'a>(env: &mut Env<'a>, at_opaque: &'a str) -> ast::Expr<'a> {
             module_name: "",
             ident: payload,
         })]),
-        roc_module::called_via::CalledVia::Space,
+        CalledVia::Space,
     ));
 
     // Inspect.tag("@opaque", [Inspect.to_inspector(payload)])
@@ -264,7 +259,7 @@ fn to_inspector<'a>(env: &mut Env<'a>, at_opaque: &'a str) -> ast::Expr<'a> {
             ident: "tag",
         }),
         &*env.arena.alloc([&*opaque_name, &*to_inspector_list]),
-        roc_module::called_via::CalledVia::Space,
+        CalledVia::Space,
     ));
 
     let fmt = "#fmt";
@@ -282,7 +277,7 @@ fn to_inspector<'a>(env: &mut Env<'a>, at_opaque: &'a str) -> ast::Expr<'a> {
                 ident: fmt,
             }),
         ]),
-        roc_module::called_via::CalledVia::Space,
+        CalledVia::Space,
     ));
 
     let custom_closure = alloc_expr(ast::Expr::Closure(

crates/compiler/can/src/desugar.rs

@@ -11,9 +11,8 @@ use roc_module::called_via::{BinOp, CalledVia};
 use roc_module::ident::ModuleName;
 use roc_parse::ast::Expr::{self, *};
 use roc_parse::ast::{
-    is_expr_suffixed, AssignedField, Collection, Defs, ModuleImportParams, Pattern,
+    is_expr_suffixed, AssignedField, Collection, Defs, ModuleImportParams, Pattern, ResultTryKind,
-    PatternApplyStyle, ResultTryKind, StrLiteral, StrSegment, TryTarget, TypeAnnotation, ValueDef,
+    StrLiteral, StrSegment, TryTarget, TypeAnnotation, ValueDef, WhenBranch,
-    WhenBranch,
 };
 use roc_problem::can::Problem;
 use roc_region::all::{Loc, Region};
@@ -50,6 +49,29 @@ fn new_op_call_expr<'a>(
                         Expr::LowLevelTry(desugared_left, ResultTryKind::KeywordPrefix),
                     );
                 }
+                PncApply(&Loc { value: Try, .. }, arguments) => {
+                    let try_fn = desugar_expr(env, scope, arguments.items.first().unwrap());
+
+                    let mut args = Vec::with_capacity_in(arguments.len(), env.arena);
+                    args.push(desugar_expr(env, scope, left));
+                    args.extend(
+                        arguments
+                            .iter()
+                            .skip(1)
+                            .map(|a| desugar_expr(env, scope, a)),
+                    );
+
+                    return Loc::at(
+                        region,
+                        Expr::LowLevelTry(
+                            env.arena.alloc(Loc::at(
+                                region,
+                                Expr::Apply(try_fn, args.into_bump_slice(), CalledVia::Try),
+                            )),
+                            ResultTryKind::KeywordPrefix,
+                        ),
+                    );
+                }
                 Apply(&Loc { value: Try, .. }, arguments, _called_via) => {
                     let try_fn = desugar_expr(env, scope, arguments.first().unwrap());
 
@@ -95,6 +117,41 @@ fn new_op_call_expr<'a>(
                         ),
                     );
                 }
+                PncApply(
+                    &Loc {
+                        value:
+                            TrySuffix {
+                                target: TryTarget::Result,
+                                expr: fn_expr,
+                            },
+                        region: fn_region,
+                    },
+                    loc_args,
+                ) => {
+                    let loc_fn = env.arena.alloc(Loc::at(fn_region, *fn_expr));
+                    let function = desugar_expr(env, scope, loc_fn);
+
+                    let mut desugared_args = Vec::with_capacity_in(loc_args.len() + 1, env.arena);
+                    desugared_args.push(desugar_expr(env, scope, left));
+                    for loc_arg in loc_args.items {
+                        desugared_args.push(desugar_expr(env, scope, loc_arg));
+                    }
+
+                    return Loc::at(
+                        region,
+                        LowLevelTry(
+                            env.arena.alloc(Loc::at(
+                                region,
+                                Expr::Apply(
+                                    function,
+                                    desugared_args.into_bump_slice(),
+                                    CalledVia::Try,
+                                ),
+                            )),
+                            ResultTryKind::OperatorSuffix,
+                        ),
+                    );
+                }
                 Apply(
                     &Loc {
                         value:
@@ -148,6 +205,16 @@ fn new_op_call_expr<'a>(
 
                     Apply(function, args, CalledVia::BinOp(Pizza))
                 }
+                PncApply(function, arguments) => {
+                    let mut args = Vec::with_capacity_in(1 + arguments.len(), env.arena);
+
+                    args.push(left);
+                    args.extend(arguments.iter());
+
+                    let args = args.into_bump_slice();
+
+                    Apply(function, args, CalledVia::BinOp(Pizza))
+                }
                 Dbg => *desugar_dbg_expr(env, scope, left, region),
                 _ => {
                     // e.g. `1 |> (if b then (\a -> a) else (\c -> c))`
@@ -178,10 +245,9 @@ fn new_op_call_expr<'a>(
                 env.arena.alloc(Loc::at(left.region, Pattern::Tag("Ok")));
             branch_1_patts.push(Loc::at(
                 left.region,
-                Pattern::Apply(
+                Pattern::PncApply(
                     branch_1_tag,
-                    branch_1_patts_args.into_bump_slice(),
+                    Collection::with_items(branch_1_patts_args.into_bump_slice()),
-                    PatternApplyStyle::ParensAndCommas,
                 ),
             ));
             let branch_one: &WhenBranch<'_> = env.arena.alloc(WhenBranch {
@@ -203,10 +269,9 @@ fn new_op_call_expr<'a>(
                 env.arena.alloc(Loc::at(left.region, Pattern::Tag("Err")));
             branch_2_patts.push(Loc::at(
                 right.region,
-                Pattern::Apply(
+                Pattern::PncApply(
                     branch_2_tag,
-                    branch_2_patts_args.into_bump_slice(),
+                    Collection::with_items(branch_2_patts_args.into_bump_slice()),
-                    PatternApplyStyle::ParensAndCommas,
                 ),
             ));
             let branch_two: &WhenBranch<'_> = env.arena.alloc(WhenBranch {
@@ -1126,6 +1191,94 @@ pub fn desugar_expr<'a>(
                 region: loc_expr.region,
             })
         }
+        PncApply(Loc { value: Dbg, .. }, loc_args) => {
+            if loc_args.is_empty() {
+                env.problem(Problem::UnappliedDbg {
+                    region: loc_expr.region,
+                });
+                env.arena.alloc(Loc {
+                    value: *desugar_invalid_dbg_expr(env, scope, loc_expr.region),
+                    region: loc_expr.region,
+                })
+            } else if loc_args.len() > 1 {
+                let args_region = Region::span_across(
+                    &loc_args.items.first().unwrap().region,
+                    &loc_args.items.last().unwrap().region,
+                );
+                env.problem(Problem::OverAppliedDbg {
+                    region: args_region,
+                });
+
+                env.arena.alloc(Loc {
+                    value: *desugar_invalid_dbg_expr(env, scope, loc_expr.region),
+                    region: loc_expr.region,
+                })
+            } else {
+                let desugared_arg = desugar_expr(env, scope, loc_args.items.first().unwrap());
+
+                env.arena.alloc(Loc {
+                    value: *desugar_dbg_expr(env, scope, desugared_arg, loc_expr.region),
+                    region: loc_expr.region,
+                })
+            }
+        }
+        PncApply(
+            Loc {
+                value: Try,
+                region: _,
+            },
+            loc_args,
+        ) => {
+            let result_expr = if loc_args.len() == 1 {
+                desugar_expr(env, scope, loc_args.items[0])
+            } else {
+                let function = desugar_expr(env, scope, loc_args.items.first().unwrap());
+                let mut desugared_args = Vec::with_capacity_in(loc_args.len() - 1, env.arena);
+                for loc_arg in &loc_args.items[1..] {
+                    desugared_args.push(desugar_expr(env, scope, loc_arg));
+                }
+
+                let args_region = Region::span_across(
+                    &loc_args.items[0].region,
+                    &loc_args.items[loc_args.items.len() - 1].region,
+                );
+
+                env.arena.alloc(Loc::at(
+                    args_region,
+                    Expr::Apply(function, desugared_args.into_bump_slice(), CalledVia::Try),
+                ))
+            };
+
+            env.arena.alloc(Loc::at(
+                loc_expr.region,
+                Expr::LowLevelTry(result_expr, ResultTryKind::KeywordPrefix),
+            ))
+        }
+        PncApply(loc_fn, loc_args) => {
+            let mut desugared_args = Vec::with_capacity_in(loc_args.len(), env.arena);
+
+            for loc_arg in loc_args.iter() {
+                let mut current = loc_arg.value;
+                let arg = loop {
+                    match current {
+                        SpaceBefore(expr, _) | SpaceAfter(expr, _) => {
+                            current = *expr;
+                        }
+                        _ => break loc_arg,
+                    }
+                };
+
+                desugared_args.push(desugar_expr(env, scope, arg));
+            }
+
+            let desugared_args = Collection::with_items(desugared_args.into_bump_slice());
+
+            env.arena.alloc(Loc {
+                value: PncApply(desugar_expr(env, scope, loc_fn), desugared_args),
+                region: loc_expr.region,
+            })
+        }
+
         When(loc_cond_expr, branches) => {
             let loc_desugared_cond = &*env.arena.alloc(desugar_expr(env, scope, loc_cond_expr));
             let mut desugared_branches = Vec::with_capacity_in(branches.len(), env.arena);
@@ -1422,7 +1575,7 @@ fn desugar_pattern<'a>(env: &mut Env<'a>, scope: &mut Scope, pattern: Pattern<'a
         | MalformedIdent(_, _)
         | QualifiedIdentifier { .. } => pattern,
 
-        Apply(tag, arg_patterns, style) => {
+        Apply(tag, arg_patterns) => {
             // Skip desugaring the tag, it should either be a Tag or OpaqueRef
             let mut desugared_arg_patterns = Vec::with_capacity_in(arg_patterns.len(), env.arena);
             for arg_pattern in arg_patterns.iter() {
@@ -1432,7 +1585,22 @@ fn desugar_pattern<'a>(env: &mut Env<'a>, scope: &mut Scope, pattern: Pattern<'a
                 });
             }
 
-            Apply(tag, desugared_arg_patterns.into_bump_slice(), style)
+            Apply(tag, desugared_arg_patterns.into_bump_slice())
+        }
+        PncApply(tag, arg_patterns) => {
+            // Skip desugaring the tag, it should either be a Tag or OpaqueRef
+            let mut desugared_arg_patterns = Vec::with_capacity_in(arg_patterns.len(), env.arena);
+            for arg_pattern in arg_patterns.iter() {
+                desugared_arg_patterns.push(Loc {
+                    region: arg_pattern.region,
+                    value: desugar_pattern(env, scope, arg_pattern.value),
+                });
+            }
+
+            PncApply(
+                tag,
+                Collection::with_items(desugared_arg_patterns.into_bump_slice()),
+            )
         }
         RecordDestructure(field_patterns) => {
             RecordDestructure(desugar_record_destructures(env, scope, field_patterns))

crates/compiler/can/src/expr.rs

@@ -11,6 +11,7 @@ use crate::pattern::{canonicalize_pattern, BindingsFromPattern, Pattern, PermitS
 use crate::procedure::{QualifiedReference, References};
 use crate::scope::{Scope, SymbolLookup};
 use crate::traverse::{walk_expr, Visitor};
+use bumpalo::collections::Vec as BumpVec;
 use roc_collections::soa::index_push_new;
 use roc_collections::{SendMap, VecMap, VecSet};
 use roc_error_macros::internal_error;
@@ -760,6 +761,166 @@ pub struct WhenBranch {
     pub redundant: RedundantMark,
 }
 
+#[allow(clippy::too_many_arguments)]
+fn canonicalize_expr_apply<'a>(
+    env: &mut Env<'a>,
+    var_store: &mut VarStore,
+    scope: &mut Scope,
+    loc_fn: &&'a Loc<ast::Expr>,
+    args: BumpVec<'a, (Variable, Loc<Expr>)>,
+    output: &mut Output,
+    region: Region,
+    application_style: CalledVia,
+) -> Expr {
+    use Expr::*;
+
+    let fn_region = loc_fn.region;
+    if let ast::Expr::OpaqueRef(name) = loc_fn.value {
+        // We treat opaques specially, since an opaque can wrap exactly one argument.
+
+        if args.is_empty() {
+            let loc_name = Loc::at(region, (*name).into());
+            let problem = roc_problem::can::RuntimeError::OpaqueNotApplied(loc_name);
+            env.problem(Problem::RuntimeError(problem.clone()));
+            RuntimeError(problem)
+        } else if args.len() > 1 {
+            let problem = roc_problem::can::RuntimeError::OpaqueAppliedToMultipleArgs(region);
+            env.problem(Problem::RuntimeError(problem.clone()));
+            RuntimeError(problem)
+        } else {
+            match scope.lookup_opaque_ref(name, loc_fn.region) {
+                Err(runtime_error) => {
+                    env.problem(Problem::RuntimeError(runtime_error.clone()));
+                    RuntimeError(runtime_error)
+                }
+                Ok((name, opaque_def)) => {
+                    let argument = Box::new(args.first().unwrap().clone());
+                    output
+                        .references
+                        .insert_type_lookup(name, QualifiedReference::Unqualified);
+
+                    let (type_arguments, lambda_set_variables, specialized_def_type) =
+                        freshen_opaque_def(var_store, opaque_def);
+
+                    OpaqueRef {
+                        opaque_var: var_store.fresh(),
+                        name,
+                        argument,
+                        specialized_def_type: Box::new(specialized_def_type),
+                        type_arguments,
+                        lambda_set_variables,
+                    }
+                }
+            }
+        }
+    } else if let ast::Expr::Crash = loc_fn.value {
+        // We treat crash specially, since crashing must be applied with one argument.
+
+        debug_assert!(!args.is_empty());
+
+        let crash = if args.len() > 1 {
+            let args_region = Region::span_across(
+                &args.first().unwrap().1.region,
+                &args.last().unwrap().1.region,
+            );
+            env.problem(Problem::OverAppliedCrash {
+                region: args_region,
+            });
+            // Still crash, just with our own message, and drop the references.
+            Crash {
+                msg: Box::new(Loc::at(
+                    region,
+                    Expr::Str(String::from("hit a crash!").into_boxed_str()),
+                )),
+                ret_var: var_store.fresh(),
+            }
+        } else {
+            let msg = args.first().unwrap();
+            Crash {
+                msg: Box::new(msg.1.clone()),
+                ret_var: var_store.fresh(),
+            }
+        };
+
+        crash
+    } else {
+        // Canonicalize the function expression and its arguments
+        let (fn_expr, fn_expr_output) =
+            canonicalize_expr(env, var_store, scope, fn_region, &loc_fn.value);
+
+        output.union(fn_expr_output);
+
+        // Default: We're not tail-calling a symbol (by name), we're tail-calling a function value.
+        output.tail_calls = vec![];
+
+        match fn_expr.value {
+            Var(symbol, _) => {
+                output.references.insert_call(symbol);
+
+                // we're tail-calling a symbol by name, check if it's the tail-callable symbol
+                if env
+                    .tailcallable_symbol
+                    .is_some_and(|tc_sym| tc_sym == symbol)
+                {
+                    output.tail_calls.push(symbol);
+                }
+
+                Call(
+                    Box::new((
+                        var_store.fresh(),
+                        fn_expr,
+                        var_store.fresh(),
+                        var_store.fresh(),
+                        var_store.fresh(),
+                    )),
+                    args.to_vec(),
+                    application_style,
+                )
+            }
+            RuntimeError(_) => {
+                // We can't call a runtime error; bail out by propagating it!
+                return fn_expr.value;
+            }
+            Tag {
+                tag_union_var: variant_var,
+                ext_var,
+                name,
+                ..
+            } => Tag {
+                tag_union_var: variant_var,
+                ext_var,
+                name,
+                arguments: args.to_vec(),
+            },
+            ZeroArgumentTag {
+                variant_var,
+                ext_var,
+                name,
+                ..
+            } => Tag {
+                tag_union_var: variant_var,
+                ext_var,
+                name,
+                arguments: args.to_vec(),
+            },
+            _ => {
+                // This could be something like ((if True then fn1 else fn2) arg1 arg2).
+                Call(
+                    Box::new((
+                        var_store.fresh(),
+                        fn_expr,
+                        var_store.fresh(),
+                        var_store.fresh(),
+                        var_store.fresh(),
+                    )),
+                    args.to_vec(),
+                    application_style,
+                )
+            }
+        }
+    }
+}
+
 pub fn canonicalize_expr<'a>(
     env: &mut Env<'a>,
     var_store: &mut VarStore,
@@ -923,13 +1084,36 @@ pub fn canonicalize_expr<'a>(
                 )
             }
         }
+        ast::Expr::PncApply(loc_fn, loc_args) => {
+            // The function's return type
+            let mut args = BumpVec::with_capacity_in(loc_args.items.len(), env.arena);
+            let mut output = Output::default();
+
+            for loc_arg in loc_args.items.iter() {
+                let (arg_expr, arg_out) =
+                    canonicalize_expr(env, var_store, scope, loc_arg.region, &loc_arg.value);
+
+                args.push((var_store.fresh(), arg_expr));
+                output.references.union_mut(&arg_out.references);
+            }
+            let value = canonicalize_expr_apply(
+                env,
+                var_store,
+                scope,
+                loc_fn,
+                args,
+                &mut output,
+                region,
+                CalledVia::Space,
+            );
+            (value, output)
+        }
         ast::Expr::Apply(loc_fn, loc_args, application_style) => {
             // The expression that evaluates to the function being called, e.g. `foo` in
             // (foo) bar baz
-            let fn_region = loc_fn.region;
 
             // The function's return type
-            let mut args = Vec::new();
+            let mut args = BumpVec::with_capacity_in(loc_args.len(), env.arena);
             let mut output = Output::default();
 
             for loc_arg in loc_args.iter() {
@@ -939,164 +1123,17 @@ pub fn canonicalize_expr<'a>(
                 args.push((var_store.fresh(), arg_expr));
                 output.references.union_mut(&arg_out.references);
             }
-
+            let value = canonicalize_expr_apply(
-            if let ast::Expr::OpaqueRef(name) = loc_fn.value {
+                env,
-                // We treat opaques specially, since an opaque can wrap exactly one argument.
+                var_store,
-
+                scope,
-                debug_assert!(!args.is_empty());
+                loc_fn,
-
+                args,
-                if args.len() > 1 {
+                &mut output,
-                    let problem =
-                        roc_problem::can::RuntimeError::OpaqueAppliedToMultipleArgs(region);
-                    env.problem(Problem::RuntimeError(problem.clone()));
-                    (RuntimeError(problem), output)
-                } else {
-                    match scope.lookup_opaque_ref(name, loc_fn.region) {
-                        Err(runtime_error) => {
-                            env.problem(Problem::RuntimeError(runtime_error.clone()));
-                            (RuntimeError(runtime_error), output)
-                        }
-                        Ok((name, opaque_def)) => {
-                            let argument = Box::new(args.pop().unwrap());
-                            output
-                                .references
-                                .insert_type_lookup(name, QualifiedReference::Unqualified);
-
-                            let (type_arguments, lambda_set_variables, specialized_def_type) =
-                                freshen_opaque_def(var_store, opaque_def);
-
-                            let opaque_ref = OpaqueRef {
-                                opaque_var: var_store.fresh(),
-                                name,
-                                argument,
-                                specialized_def_type: Box::new(specialized_def_type),
-                                type_arguments,
-                                lambda_set_variables,
-                            };
-
-                            (opaque_ref, output)
-                        }
-                    }
-                }
-            } else if let ast::Expr::Crash = loc_fn.value {
-                // We treat crash specially, since crashing must be applied with one argument.
-
-                debug_assert!(!args.is_empty());
-
-                let mut args = Vec::new();
-                let mut output = Output::default();
-
-                for loc_arg in loc_args.iter() {
-                    let (arg_expr, arg_out) =
-                        canonicalize_expr(env, var_store, scope, loc_arg.region, &loc_arg.value);
-
-                    args.push(arg_expr);
-                    output.references.union_mut(&arg_out.references);
-                }
-
-                let crash = if args.len() > 1 {
-                    let args_region = Region::span_across(
-                        &loc_args.first().unwrap().region,
-                        &loc_args.last().unwrap().region,
-                    );
-                    env.problem(Problem::OverAppliedCrash {
-                        region: args_region,
-                    });
-                    // Still crash, just with our own message, and drop the references.
-                    Crash {
-                        msg: Box::new(Loc::at(
                 region,
-                            Expr::Str(String::from("hit a crash!").into_boxed_str()),
-                        )),
-                        ret_var: var_store.fresh(),
-                    }
-                } else {
-                    let msg = args.pop().unwrap();
-                    Crash {
-                        msg: Box::new(msg),
-                        ret_var: var_store.fresh(),
-                    }
-                };
-
-                (crash, output)
-            } else {
-                // Canonicalize the function expression and its arguments
-                let (fn_expr, fn_expr_output) =
-                    canonicalize_expr(env, var_store, scope, fn_region, &loc_fn.value);
-
-                output.union(fn_expr_output);
-
-                // Default: We're not tail-calling a symbol (by name), we're tail-calling a function value.
-                output.tail_calls = vec![];
-
-                let expr = match fn_expr.value {
-                    Var(symbol, _) => {
-                        output.references.insert_call(symbol);
-
-                        // we're tail-calling a symbol by name, check if it's the tail-callable symbol
-                        if env
-                            .tailcallable_symbol
-                            .is_some_and(|tc_sym| tc_sym == symbol)
-                        {
-                            output.tail_calls.push(symbol);
-                        }
-
-                        Call(
-                            Box::new((
-                                var_store.fresh(),
-                                fn_expr,
-                                var_store.fresh(),
-                                var_store.fresh(),
-                                var_store.fresh(),
-                            )),
-                            args,
                 *application_style,
-                        )
+            );
-                    }
+            (value, output)
-                    RuntimeError(_) => {
-                        // We can't call a runtime error; bail out by propagating it!
-                        return (fn_expr, output);
-                    }
-                    Tag {
-                        tag_union_var: variant_var,
-                        ext_var,
-                        name,
-                        ..
-                    } => Tag {
-                        tag_union_var: variant_var,
-                        ext_var,
-                        name,
-                        arguments: args,
-                    },
-                    ZeroArgumentTag {
-                        variant_var,
-                        ext_var,
-                        name,
-                        ..
-                    } => Tag {
-                        tag_union_var: variant_var,
-                        ext_var,
-                        name,
-                        arguments: args,
-                    },
-                    _ => {
-                        // This could be something like ((if True then fn1 else fn2) arg1 arg2).
-                        Call(
-                            Box::new((
-                                var_store.fresh(),
-                                fn_expr,
-                                var_store.fresh(),
-                                var_store.fresh(),
-                                var_store.fresh(),
-                            )),
-                            args,
-                            *application_style,
-                        )
-                    }
-                };
-
-                (expr, output)
-            }
         }
         ast::Expr::Var { module_name, ident } => {
             canonicalize_var_lookup(env, var_store, scope, module_name, ident, region)
@@ -2266,6 +2303,12 @@ pub fn is_valid_interpolation(expr: &ast::Expr<'_>) -> bool {
                     .iter()
                     .all(|loc_arg| is_valid_interpolation(&loc_arg.value))
         }
+        ast::Expr::PncApply(loc_expr, args) => {
+            is_valid_interpolation(&loc_expr.value)
+                && args
+                    .iter()
+                    .all(|loc_arg| is_valid_interpolation(&loc_arg.value))
+        }
         ast::Expr::BinOps(loc_exprs, loc_expr) => {
             is_valid_interpolation(&loc_expr.value)
                 && loc_exprs

crates/compiler/can/src/pattern.rs

@@ -6,6 +6,7 @@ use crate::num::{
     ParsedNumResult,
 };
 use crate::scope::{PendingAbilitiesInScope, Scope};
+use bumpalo::collections::Vec as BumpVec;
 use roc_exhaustive::ListArity;
 use roc_module::ident::{Ident, Lowercase, TagName};
 use roc_module::symbol::Symbol;
@@ -367,6 +368,75 @@ fn canonicalize_pattern_symbol(
     }
 }
 
+pub fn canonicalize_apply_tag<'a>(
+    tag: Loc<ast::Pattern<'a>>,
+    env: &mut Env<'a>,
+    var_store: &mut VarStore,
+    scope: &mut Scope,
+    output: &mut Output,
+    region: Region,
+    can_patterns: BumpVec<(Variable, Loc<Pattern>)>,
+) -> Pattern {
+    use ast::Pattern::*;
+    match tag.value {
+        Tag(name) => {
+            let tag_name = TagName(name.into());
+            Pattern::AppliedTag {
+                whole_var: var_store.fresh(),
+                ext_var: var_store.fresh(),
+                tag_name,
+                arguments: can_patterns.to_vec(),
+            }
+        }
+
+        OpaqueRef(name) => match scope.lookup_opaque_ref(name, tag.region) {
+            Ok((opaque, opaque_def)) => {
+                debug_assert!(!can_patterns.is_empty());
+
+                if can_patterns.len() > 1 {
+                    env.problem(Problem::RuntimeError(
+                        RuntimeError::OpaqueAppliedToMultipleArgs(region),
+                    ));
+
+                    Pattern::UnsupportedPattern(region)
+                } else {
+                    let argument = Box::new(can_patterns[0].clone());
+
+                    let (type_arguments, lambda_set_variables, specialized_def_type) =
+                        freshen_opaque_def(var_store, opaque_def);
+
+                    output.references.insert_type_lookup(
+                        opaque,
+                        crate::procedure::QualifiedReference::Unqualified,
+                    );
+
+                    Pattern::UnwrappedOpaque {
+                        whole_var: var_store.fresh(),
+                        opaque,
+                        argument,
+                        specialized_def_type: Box::new(specialized_def_type),
+                        type_arguments,
+                        lambda_set_variables,
+                    }
+                }
+            }
+            Err(runtime_error) => {
+                env.problem(Problem::RuntimeError(runtime_error));
+
+                Pattern::OpaqueNotInScope(Loc::at(tag.region, name.into()))
+            }
+        },
+        _ => {
+            env.problem(Problem::RuntimeError(RuntimeError::MalformedPattern(
+                MalformedPatternProblem::CantApplyPattern,
+                tag.region,
+            )));
+
+            Pattern::UnsupportedPattern(region)
+        }
+    }
+}
+
 #[allow(clippy::too_many_arguments)]
 pub fn canonicalize_pattern<'a>(
     env: &mut Env<'a>,
@@ -411,9 +481,9 @@ pub fn canonicalize_pattern<'a>(
             )));
             Pattern::UnsupportedPattern(region)
         }
-        Apply(tag, patterns, _) => {
+        PncApply(tag, patterns) => {
-            let mut can_patterns = Vec::with_capacity(patterns.len());
+            let mut can_patterns = BumpVec::with_capacity_in(patterns.len(), env.arena);
-            for loc_pattern in *patterns {
+            for loc_pattern in patterns.items.iter() {
                 let can_pattern = canonicalize_pattern(
                     env,
                     var_store,
@@ -428,63 +498,25 @@ pub fn canonicalize_pattern<'a>(
                 can_patterns.push((var_store.fresh(), can_pattern));
             }
 
-            match tag.value {
+            canonicalize_apply_tag(**tag, env, var_store, scope, output, region, can_patterns)
-                Tag(name) => {
-                    let tag_name = TagName(name.into());
-                    Pattern::AppliedTag {
-                        whole_var: var_store.fresh(),
-                        ext_var: var_store.fresh(),
-                        tag_name,
-                        arguments: can_patterns,
         }
-                }
+        Apply(tag, patterns) => {
-
+            let mut can_patterns = BumpVec::with_capacity_in(patterns.len(), env.arena);
-                OpaqueRef(name) => match scope.lookup_opaque_ref(name, tag.region) {
+            for loc_pattern in *patterns {
-                    Ok((opaque, opaque_def)) => {
+                let can_pattern = canonicalize_pattern(
-                        debug_assert!(!can_patterns.is_empty());
+                    env,
-
+                    var_store,
-                        if can_patterns.len() > 1 {
+                    scope,
-                            env.problem(Problem::RuntimeError(
+                    output,
-                                RuntimeError::OpaqueAppliedToMultipleArgs(region),
+                    pattern_type,
-                            ));
+                    &loc_pattern.value,
-
+                    loc_pattern.region,
-                            Pattern::UnsupportedPattern(region)
+                    permit_shadows,
-                        } else {
-                            let argument = Box::new(can_patterns.pop().unwrap());
-
-                            let (type_arguments, lambda_set_variables, specialized_def_type) =
-                                freshen_opaque_def(var_store, opaque_def);
-
-                            output.references.insert_type_lookup(
-                                opaque,
-                                crate::procedure::QualifiedReference::Unqualified,
                 );
 
-                            Pattern::UnwrappedOpaque {
+                can_patterns.push((var_store.fresh(), can_pattern));
-                                whole_var: var_store.fresh(),
-                                opaque,
-                                argument,
-                                specialized_def_type: Box::new(specialized_def_type),
-                                type_arguments,
-                                lambda_set_variables,
-                            }
-                        }
-                    }
-                    Err(runtime_error) => {
-                        env.problem(Problem::RuntimeError(runtime_error));
-
-                        Pattern::OpaqueNotInScope(Loc::at(tag.region, name.into()))
-                    }
-                },
-                _ => {
-                    env.problem(Problem::RuntimeError(RuntimeError::MalformedPattern(
-                        MalformedPatternProblem::CantApplyPattern,
-                        tag.region,
-                    )));
-
-                    Pattern::UnsupportedPattern(region)
-                }
             }
+            canonicalize_apply_tag(**tag, env, var_store, scope, output, region, can_patterns)
         }
 
         &FloatLiteral(str) => match pattern_type {

crates/compiler/can/tests/snapshots/test_suffixed__suffixed_tests__simple_double_question.snap

@@ -88,7 +88,7 @@ Defs {
                                                             [
                                                                 WhenBranch {
                                                                     patterns: [
-                                                                        @24-32 Apply(
+                                                                        @24-32 PncApply(
                                                                             @24-32 Tag(
                                                                                 "Ok",
                                                                             ),
@@ -97,7 +97,6 @@ Defs {
                                                                                     ident: "success_BRANCH1_24_32",
                                                                                 },
                                                                             ],
-                                                                            ParensAndCommas,
                                                                         ),
                                                                     ],
                                                                     value: @24-32 Var {
@@ -108,7 +107,7 @@ Defs {
                                                                 },
                                                                 WhenBranch {
                                                                     patterns: [
-                                                                        @36-39 Apply(
+                                                                        @36-39 PncApply(
                                                                             @24-32 Tag(
                                                                                 "Err",
                                                                             ),
@@ -117,7 +116,6 @@ Defs {
                                                                                     "",
                                                                                 ),
                                                                             ],
-                                                                            ParensAndCommas,
                                                                         ),
                                                                     ],
                                                                     value: @36-39 Num(

crates/compiler/can/tests/snapshots/test_suffixed__suffixed_tests__trailing_suffix_inside_when.snap

@@ -78,7 +78,6 @@ Defs {
                                                     ident: "name",
                                                 },
                                             ],
-                                            Whitespace,
                                         ),
                                     ],
                                     value: @125-154 Apply(

crates/compiler/fmt/src/def.rs

@@ -19,8 +19,8 @@ use roc_error_macros::internal_error;
 use roc_parse::ast::{
     AbilityMember, Defs, Expr, ExtractSpaces, ImportAlias, ImportAsKeyword, ImportExposingKeyword,
     ImportedModuleName, IngestedFileAnnotation, IngestedFileImport, ModuleImport,
-    ModuleImportParams, Pattern, PatternApplyStyle, Spaces, SpacesBefore, StrLiteral,
+    ModuleImportParams, Pattern, Spaces, SpacesBefore, StrLiteral, TypeAnnotation, TypeDef,
-    TypeAnnotation, TypeDef, TypeHeader, ValueDef,
+    TypeHeader, ValueDef,
 };
 use roc_parse::expr::merge_spaces;
 use roc_parse::header::Keyword;
@@ -556,7 +556,8 @@ impl<'a> Formattable for TypeHeader<'a> {
             Parens::NotNeeded,
             indent,
             self.vars.iter().any(|v| v.is_multiline()),
-            PatternApplyStyle::Whitespace,
+            false,
+            None,
         );
         buf.flags = old_flags;
     }
@@ -569,7 +570,6 @@ fn type_head_lift_spaces<'a, 'b: 'a>(
     let pat = Pattern::Apply(
         arena.alloc(Loc::at(head.name.region, Pattern::Tag(head.name.value))),
         head.vars,
-        PatternApplyStyle::Whitespace,
     );
 
     pattern_lift_spaces(arena, &pat)
@@ -891,9 +891,7 @@ impl<'a> Formattable for ValueDef<'a> {
 fn ann_pattern_needs_parens(value: &Pattern<'_>) -> bool {
     match value.extract_spaces().item {
         Pattern::Tag(_) => true,
-        Pattern::Apply(func, _args, _style)
+        Pattern::Apply(func, _args) if matches!(func.extract_spaces().item, Pattern::Tag(..)) => {
-            if matches!(func.extract_spaces().item, Pattern::Tag(..)) =>
-        {
             true
         }
         _ => false,
@@ -1085,6 +1083,13 @@ pub fn fmt_body<'a>(
                     ..
                 },
                 ..,
+            )
+            | Expr::PncApply(
+                Loc {
+                    value: Expr::Str(StrLiteral::Block(..)),
+                    ..
+                },
+                ..,
             ) => {
                 buf.spaces(1);
                 body.format_with_options(buf, Parens::NotNeeded, Newlines::Yes, indent + INDENT);
@@ -1148,6 +1153,7 @@ fn starts_with_expect_ident(expr: &Expr<'_>) -> bool {
     // If we removed the `{}=` in this case, that would change the meaning
     match expr {
         Expr::Apply(inner, _, _) => starts_with_expect_ident(&inner.value),
+        Expr::PncApply(inner, _) => starts_with_expect_ident(&inner.value),
         Expr::Var { module_name, ident } => {
             module_name.is_empty() && (*ident == "expect" || *ident == "expect!")
         }
@@ -1162,6 +1168,7 @@ pub fn starts_with_block_string_literal(expr: &Expr<'_>) -> bool {
             starts_with_block_string_literal(inner)
         }
         Expr::Apply(inner, _, _) => starts_with_block_string_literal(&inner.value),
+        Expr::PncApply(inner, _) => starts_with_block_string_literal(&inner.value),
         Expr::TrySuffix { target: _, expr } => starts_with_block_string_literal(expr),
         _ => false,
     }

crates/compiler/fmt/src/expr.rs

@@ -11,7 +11,7 @@ use crate::spaces::{
 use crate::Buf;
 use bumpalo::collections::Vec;
 use bumpalo::Bump;
-use roc_module::called_via::{self, BinOp, CalledVia, UnaryOp};
+use roc_module::called_via::{self, BinOp, UnaryOp};
 use roc_parse::ast::{
     AssignedField, Base, Collection, CommentOrNewline, Expr, ExtractSpaces, Pattern, Spaceable,
     Spaces, SpacesAfter, SpacesBefore, TryTarget, WhenBranch,
@@ -91,13 +91,23 @@ fn format_expr_only(
             buf.indent(indent);
             buf.push_str("try");
         }
-        Expr::Apply(loc_expr, loc_args, called_via::CalledVia::ParensAndCommas) => {
+        Expr::PncApply(
-            fmt_apply(loc_expr, loc_args, indent, buf, true);
+            loc_expr @ Loc {
+                value: Expr::Dbg, ..
+            },
+            loc_args,
+        ) => {
+            fmt_apply(loc_expr, loc_args.items, indent, buf);
+        }
+        Expr::PncApply(loc_expr, loc_args) => {
+            fmt_pnc_apply(loc_expr, loc_args, indent, buf);
         }
         Expr::Apply(loc_expr, loc_args, _) => {
             let apply_needs_parens = parens == Parens::InApply || parens == Parens::InApplyLastArg;
-            if buf.flags().parens_and_commas || !apply_needs_parens || loc_args.is_empty() {
+            if buf.flags().parens_and_commas {
-                fmt_apply(loc_expr, loc_args, indent, buf, false);
+                fmt_pnc_apply(loc_expr, &Collection::with_items(loc_args), indent, buf);
+            } else if !apply_needs_parens || loc_args.is_empty() {
+                fmt_apply(loc_expr, loc_args, indent, buf);
             } else {
                 fmt_parens(item, buf, indent);
             }
@@ -519,6 +529,12 @@ pub fn expr_is_multiline(me: &Expr<'_>, comments_only: bool) -> bool {
                     .iter()
                     .any(|loc_arg| expr_is_multiline(&loc_arg.value, comments_only))
         }
+        Expr::PncApply(loc_expr, args) => {
+            expr_is_multiline(&loc_expr.value, comments_only)
+                || args
+                    .iter()
+                    .any(|loc_arg| expr_is_multiline(&loc_arg.value, comments_only))
+        }
 
         Expr::DbgStmt { .. } => true,
         Expr::LowLevelDbg(_, _, _) => {
@@ -639,13 +655,28 @@ fn requires_space_after_unary(item: &Expr<'_>) -> bool {
     }
 }
 
+fn fmt_pnc_apply(
+    loc_expr: &Loc<Expr<'_>>,
+    loc_args: &Collection<'_, &Loc<Expr<'_>>>,
+    indent: u16,
+    buf: &mut Buf<'_>,
+) {
+    let expr = expr_lift_spaces(Parens::InApply, buf.text.bump(), &loc_expr.value);
+
+    if !expr.before.is_empty() {
+        format_spaces(buf, expr.before, Newlines::Yes, indent);
+    }
+    expr.item
+        .format_with_options(buf, Parens::InApply, Newlines::Yes, indent);
+    fmt_expr_collection(buf, indent, Braces::Round, *loc_args, Newlines::No);
+}
+
 fn fmt_apply(
     loc_expr: &Loc<Expr<'_>>,
     loc_args: &[&Loc<Expr<'_>>],
 
     indent: u16,
     buf: &mut Buf<'_>,
-    expr_used_commas_and_parens: bool,
 ) {
     // should_reflow_outdentable, aka should we transform this:
     //
@@ -665,7 +696,6 @@ fn fmt_apply(
     //   2,
     // ]
     // ```
-    let use_commas_and_parens = expr_used_commas_and_parens || buf.flags().parens_and_commas;
     let should_reflow_outdentable = loc_expr.extract_spaces().after.is_empty()
         && except_last(loc_args).all(|a| !a.is_multiline())
         && loc_args
@@ -701,23 +731,17 @@ fn fmt_apply(
     if !expr.before.is_empty() {
         format_spaces(buf, expr.before, Newlines::Yes, indent);
     }
+
     expr.item
         .format_with_options(buf, Parens::InApply, Newlines::Yes, indent);
 
-    if use_commas_and_parens {
-        buf.push('(');
-    }
-
     let mut last_after = expr.after;
 
     for (i, loc_arg) in loc_args.iter().enumerate() {
         let is_last_arg = i == loc_args.len() - 1;
-        let is_first_arg = i == 0;
 
         let arg = expr_lift_spaces(
-            if use_commas_and_parens {
+            if is_last_arg {
-                Parens::NotNeeded
-            } else if is_last_arg {
                 Parens::InApplyLastArg
             } else {
                 Parens::InApply
@@ -738,7 +762,7 @@ fn fmt_apply(
         last_after = arg.after;
         if needs_indent {
             buf.ensure_ends_with_newline();
-        } else if !(is_first_arg && use_commas_and_parens) {
+        } else {
             buf.spaces(1);
         }
 
@@ -746,34 +770,13 @@ fn fmt_apply(
         {
             fmt_parens(&arg.item, buf, arg_indent);
         } else {
-            format_expr_only(
+            format_expr_only(&arg.item, buf, Parens::InApply, Newlines::Yes, arg_indent);
-                &arg.item,
-                buf,
-                if use_commas_and_parens {
-                    Parens::NotNeeded
-                } else {
-                    Parens::InApply
-                },
-                Newlines::Yes,
-                arg_indent,
-            );
-        }
-        if use_commas_and_parens && (!is_last_arg || needs_indent) {
-            buf.push(',');
         }
     }
 
     if !last_after.is_empty() {
         format_spaces(buf, last_after, Newlines::Yes, arg_indent);
     }
-
-    if use_commas_and_parens {
-        if needs_indent {
-            buf.ensure_ends_with_newline();
-            buf.indent(indent);
-        }
-        buf.push(')');
-    }
 }
 
 fn is_outdentable_collection(expr: &Expr<'_>) -> bool {
@@ -1038,16 +1041,12 @@ pub fn expr_lift_spaces<'a, 'b: 'a>(
     expr: &Expr<'b>,
 ) -> Spaces<'a, Expr<'a>> {
     match expr {
-        Expr::Apply(func, args, CalledVia::ParensAndCommas) => {
+        Expr::PncApply(func, args) => {
-            let lifted = expr_lift_spaces_before(Parens::NotNeeded, arena, &func.value);
+            let lifted = expr_lift_spaces_before(Parens::InApply, arena, &func.value);
 
             Spaces {
                 before: lifted.before,
-                item: Expr::Apply(
+                item: Expr::PncApply(arena.alloc(Loc::at(func.region, lifted.item)), *args),
-                    arena.alloc(Loc::at(func.region, lifted.item)),
-                    args,
-                    CalledVia::ParensAndCommas,
-                ),
                 after: arena.alloc([]),
             }
         }

crates/compiler/fmt/src/pattern.rs

@@ -7,8 +7,7 @@ use crate::spaces::{fmt_comments_only, fmt_spaces, NewlineAt, INDENT};
 use crate::Buf;
 use bumpalo::Bump;
 use roc_parse::ast::{
-    Base, CommentOrNewline, Pattern, PatternApplyStyle, PatternAs, Spaceable, Spaces, SpacesAfter,
+    Base, CommentOrNewline, Pattern, PatternAs, Spaceable, Spaces, SpacesAfter, SpacesBefore,
-    SpacesBefore,
 };
 use roc_parse::expr::merge_spaces;
 use roc_region::all::Loc;
@@ -73,9 +72,14 @@ impl<'a> Formattable for Pattern<'a> {
                 }
             },
             Pattern::StrLiteral(literal) => is_str_multiline(literal),
-            Pattern::Apply(pat, args, _) => {
+            Pattern::Apply(pat, args) => {
                 pat.is_multiline() || args.iter().any(|a| a.is_multiline())
             }
+            Pattern::PncApply(pat, args) => {
+                pat.is_multiline()
+                    || args.iter().any(|a| a.is_multiline())
+                    || !args.final_comments().is_empty()
+            }
 
             Pattern::Identifier { .. }
             | Pattern::Tag(_)
@@ -163,22 +167,19 @@ fn fmt_pattern_only(
             buf.indent(indent);
             buf.push_str(name);
         }
-        Pattern::Apply(
+        Pattern::PncApply(loc_pattern, loc_arg_patterns) => {
-            loc_pattern,
-            loc_arg_patterns,
-            style @ PatternApplyStyle::ParensAndCommas,
-        ) => {
             pattern_fmt_apply(
                 buf,
                 loc_pattern.value,
-                loc_arg_patterns,
+                loc_arg_patterns.items,
                 Parens::NotNeeded,
                 indent,
                 is_multiline,
-                *style,
+                true,
+                Some(loc_arg_patterns.final_comments()),
             );
         }
-        Pattern::Apply(loc_pattern, loc_arg_patterns, style) => {
+        Pattern::Apply(loc_pattern, loc_arg_patterns) => {
             pattern_fmt_apply(
                 buf,
                 loc_pattern.value,
@@ -186,7 +187,8 @@ fn fmt_pattern_only(
                 parens,
                 indent,
                 is_multiline,
-                *style,
+                false,
+                None,
             );
         }
         Pattern::RecordDestructure(loc_patterns) => {
@@ -455,6 +457,7 @@ fn fmt_pattern_only(
     }
 }
 
+#[allow(clippy::too_many_arguments)]
 pub fn pattern_fmt_apply(
     buf: &mut Buf<'_>,
     func: Pattern<'_>,
@@ -462,10 +465,10 @@ pub fn pattern_fmt_apply(
     parens: Parens,
     indent: u16,
     is_multiline: bool,
-    style: PatternApplyStyle,
+    is_pnc: bool,
+    final_comments: Option<&[CommentOrNewline]>,
 ) {
-    let use_commas_and_parens =
+    let use_commas_and_parens = is_pnc || buf.flags().parens_and_commas;
-        matches!(style, PatternApplyStyle::ParensAndCommas) || buf.flags().parens_and_commas;
     buf.indent(indent);
     // Sometimes, an Apply pattern needs parens around it.
     // In particular when an Apply's argument is itself an Apply (> 0) arguments
@@ -560,7 +563,7 @@ pub fn pattern_fmt_apply(
             buf.push_str("(implements)");
         } else {
             fmt_pattern_only(&arg.item, buf, parens, indent_more, arg.item.is_multiline());
-            if use_commas_and_parens && (!is_last_arg || add_newlines) {
+            if use_commas_and_parens && (!is_last_arg || is_multiline) {
                 buf.push(',');
             }
         }
@@ -570,6 +573,13 @@ pub fn pattern_fmt_apply(
         add_newlines |= was_multiline;
     }
 
+    if let Some(comments) = final_comments {
+        if !is_multiline {
+            fmt_comments_only(buf, comments.iter(), NewlineAt::Bottom, indent_more);
+        } else {
+            fmt_spaces(buf, comments.iter(), indent_more);
+        }
+    }
     if !last_after.is_empty() {
         if !is_multiline {
             fmt_comments_only(buf, last_after.iter(), NewlineAt::Bottom, indent_more)
@@ -578,7 +588,21 @@ pub fn pattern_fmt_apply(
         }
     }
 
-    if parens || use_commas_and_parens {
+    if use_commas_and_parens {
+        if is_multiline {
+            buf.ensure_ends_with_newline();
+            buf.indent(indent);
+        }
+        if buf.ends_with_newline() {
+            buf.indent(indent);
+        }
+        if buf.ends_with_newline() {
+            buf.indent(indent);
+        }
+        buf.push(')');
+    }
+
+    if parens {
         buf.push(')');
     }
 }
@@ -632,8 +656,9 @@ fn pattern_prec(pat: Pattern<'_>) -> Prec {
         | Pattern::SingleQuote(_)
         | Pattern::Tuple(..)
         | Pattern::List(..)
-        | Pattern::ListRest(_) => Prec::Term,
+        | Pattern::ListRest(_)
-        Pattern::Apply(_, _, _) | Pattern::As(_, _) => Prec::Apply,
+        | Pattern::PncApply(_, _) => Prec::Term,
+        Pattern::Apply(_, _) | Pattern::As(_, _) => Prec::Apply,
         Pattern::SpaceBefore(inner, _) | Pattern::SpaceAfter(inner, _) => pattern_prec(*inner),
         Pattern::Malformed(_) | Pattern::MalformedIdent(..) => Prec::Term,
     }
@@ -653,7 +678,7 @@ pub fn pattern_lift_spaces<'a, 'b: 'a>(
     pat: &Pattern<'b>,
 ) -> Spaces<'a, Pattern<'a>> {
     match pat {
-        Pattern::Apply(func, args, style) => {
+        Pattern::Apply(func, args) => {
             let func_lifted = pattern_lift_spaces(arena, &func.value);
 
             let args = arena.alloc_slice_copy(args);
@@ -688,10 +713,19 @@ pub fn pattern_lift_spaces<'a, 'b: 'a>(
             };
             Spaces {
                 before,
-                item: Pattern::Apply(arena.alloc(func), args, *style),
+                item: Pattern::Apply(arena.alloc(func), args),
                 after,
             }
         }
+        Pattern::PncApply(func, args) => {
+            let func_lifted = pattern_lift_spaces_before(arena, &func.value);
+
+            Spaces {
+                before: func_lifted.before,
+                item: Pattern::PncApply(arena.alloc(func), *args),
+                after: &[],
+            }
+        }
         Pattern::OptionalField(name, expr) => {
             let lifted = expr_lift_spaces_after(Parens::NotNeeded, arena, &expr.value);
             Spaces {
@@ -748,7 +782,9 @@ fn handle_multiline_str_spaces<'a>(pat: &Pattern<'_>, before: &mut &'a [CommentO
 
 fn starts_with_block_str(item: &Pattern<'_>) -> bool {
     match item {
-        Pattern::As(inner, _) | Pattern::Apply(inner, _, _) => starts_with_block_str(&inner.value),
+        Pattern::As(inner, _) | Pattern::Apply(inner, _) | Pattern::PncApply(inner, _) => {
+            starts_with_block_str(&inner.value)
+        }
         Pattern::SpaceBefore(inner, _) | Pattern::SpaceAfter(inner, _) => {
             starts_with_block_str(inner)
         }

crates/compiler/module/src/called_via.rs

@@ -68,9 +68,6 @@ pub enum CalledVia {
     /// Calling with space, e.g. (foo bar)
     Space,
 
-    /// Calling parens-and-comms style, e.g. foo(bar)
-    ParensAndCommas,
-
     /// Calling with an operator, e.g. (bar |> foo) or (1 + 2)
     BinOp(BinOp),
 

crates/compiler/parse/src/ast.rs

@@ -554,6 +554,7 @@ pub enum Expr<'a> {
     /// To apply by name, do Apply(Var(...), ...)
     /// To apply a tag by name, do Apply(Tag(...), ...)
     Apply(&'a Loc<Expr<'a>>, &'a [&'a Loc<Expr<'a>>], CalledVia),
+    PncApply(&'a Loc<Expr<'a>>, Collection<'a, &'a Loc<Expr<'a>>>),
     BinOps(&'a [(Loc<Expr<'a>>, Loc<BinOp>)], &'a Loc<Expr<'a>>),
     UnaryOp(&'a Loc<Expr<'a>>, Loc<UnaryOp>),
 
@@ -631,6 +632,7 @@ pub fn is_top_level_suffixed(expr: &Expr) -> bool {
     match expr {
         Expr::TrySuffix { .. } => true,
         Expr::Apply(a, _, _) => is_top_level_suffixed(&a.value),
+        Expr::PncApply(a, _) => is_top_level_suffixed(&a.value),
         Expr::SpaceBefore(a, _) => is_top_level_suffixed(a),
         Expr::SpaceAfter(a, _) => is_top_level_suffixed(a),
         _ => false,
@@ -653,6 +655,15 @@ pub fn is_expr_suffixed(expr: &Expr) -> bool {
             any_args_suffixed || is_function_suffixed
         }
 
+        Expr::PncApply(sub_loc_expr, apply_arg_collection) => {
+            let is_function_suffixed = is_expr_suffixed(&sub_loc_expr.value);
+            let any_args_suffixed = apply_arg_collection
+                .iter()
+                .any(|arg| is_expr_suffixed(&arg.value));
+
+            any_args_suffixed || is_function_suffixed
+        }
+
         // expression in a pipeline, `"hi" |> say!`
         Expr::BinOps(firsts, last) => {
             firsts
@@ -1021,6 +1032,14 @@ impl<'a, 'b> RecursiveValueDefIter<'a, 'b> {
                         expr_stack.push(&loc_expr.value);
                     }
                 }
+                PncApply(fun, args) => {
+                    expr_stack.reserve(args.len() + 1);
+                    expr_stack.push(&fun.value);
+
+                    for loc_expr in args.iter() {
+                        expr_stack.push(&loc_expr.value);
+                    }
+                }
                 BinOps(ops, expr) => {
                     expr_stack.reserve(ops.len() + 1);
 
@@ -1725,12 +1744,6 @@ impl<'a> PatternAs<'a> {
     }
 }
 
-#[derive(Clone, Copy, Debug, PartialEq)]
-pub enum PatternApplyStyle {
-    Whitespace,
-    ParensAndCommas,
-}
-
 #[derive(Clone, Copy, Debug, PartialEq)]
 pub enum Pattern<'a> {
     // Identifier
@@ -1746,11 +1759,9 @@ pub enum Pattern<'a> {
 
     OpaqueRef(&'a str),
 
-    Apply(
+    Apply(&'a Loc<Pattern<'a>>, &'a [Loc<Pattern<'a>>]),
-        &'a Loc<Pattern<'a>>,
+
-        &'a [Loc<Pattern<'a>>],
+    PncApply(&'a Loc<Pattern<'a>>, Collection<'a, Loc<Pattern<'a>>>),
-        PatternApplyStyle,
-    ),
 
     /// This is Located<Pattern> rather than Located<str> so we can record comments
     /// around the destructured names, e.g. { x ### x does stuff ###, y }
@@ -1831,8 +1842,34 @@ impl<'a> Pattern<'a> {
                     false
                 }
             }
-            Apply(constructor_x, args_x, _) => {
+            Apply(constructor_x, args_x) => {
-                if let Apply(constructor_y, args_y, _) = other {
+                if let Apply(constructor_y, args_y) = other {
+                    let equivalent_args = args_x
+                        .iter()
+                        .zip(args_y.iter())
+                        .all(|(p, q)| p.value.equivalent(&q.value));
+
+                    constructor_x.value.equivalent(&constructor_y.value) && equivalent_args
+                } else if let PncApply(constructor_y, args_y) = other {
+                    let equivalent_args = args_x
+                        .iter()
+                        .zip(args_y.iter())
+                        .all(|(p, q)| p.value.equivalent(&q.value));
+
+                    constructor_x.value.equivalent(&constructor_y.value) && equivalent_args
+                } else {
+                    false
+                }
+            }
+            PncApply(constructor_x, args_x) => {
+                if let PncApply(constructor_y, args_y) = other {
+                    let equivalent_args = args_x
+                        .iter()
+                        .zip(args_y.iter())
+                        .all(|(p, q)| p.value.equivalent(&q.value));
+
+                    constructor_x.value.equivalent(&constructor_y.value) && equivalent_args
+                } else if let Apply(constructor_y, args_y) = other {
                     let equivalent_args = args_x
                         .iter()
                         .zip(args_y.iter())
@@ -2554,6 +2591,7 @@ impl<'a> Malformed for Expr<'a> {
             LowLevelTry(loc_expr, _) => loc_expr.is_malformed(),
             Return(return_value, after_return) => return_value.is_malformed() || after_return.is_some_and(|ar| ar.is_malformed()),
             Apply(func, args, _) => func.is_malformed() || args.iter().any(|arg| arg.is_malformed()),
+            PncApply(func, args) => func.is_malformed() || args.iter().any(|arg| arg.is_malformed()),
             BinOps(firsts, last) => firsts.iter().any(|(expr, _)| expr.is_malformed()) || last.is_malformed(),
             UnaryOp(expr, _) => expr.is_malformed(),
             If { if_thens, final_else, ..} => if_thens.iter().any(|(cond, body)| cond.is_malformed() || body.is_malformed()) || final_else.is_malformed(),
@@ -2650,7 +2688,8 @@ impl<'a> Malformed for Pattern<'a> {
             Identifier{ .. } |
             Tag(_) |
             OpaqueRef(_) => false,
-            Apply(func, args, _) => func.is_malformed() || args.iter().any(|arg| arg.is_malformed()),
+            Apply(func, args) => func.is_malformed() || args.iter().any(|arg| arg.is_malformed()),
+            PncApply(func, args) => func.is_malformed() || args.iter().any(|arg| arg.is_malformed()),
             RecordDestructure(items) => items.iter().any(|item| item.is_malformed()),
             RequiredField(_, pat) => pat.is_malformed(),
             OptionalField(_, expr) => expr.is_malformed(),

crates/compiler/parse/src/expr.rs

@@ -2,8 +2,8 @@ use crate::ast::{
     is_expr_suffixed, AssignedField, Collection, CommentOrNewline, Defs, Expr, ExtractSpaces,
     Implements, ImplementsAbilities, ImportAlias, ImportAsKeyword, ImportExposingKeyword,
     ImportedModuleName, IngestedFileAnnotation, IngestedFileImport, ModuleImport,
-    ModuleImportParams, Pattern, PatternApplyStyle, Spaceable, Spaced, Spaces, SpacesBefore,
+    ModuleImportParams, Pattern, Spaceable, Spaced, Spaces, SpacesBefore, TryTarget,
-    TryTarget, TypeAnnotation, TypeDef, TypeHeader, ValueDef,
+    TypeAnnotation, TypeDef, TypeHeader, ValueDef,
 };
 use crate::blankspace::{
     loc_space0_e, require_newline_or_eof, space0_after_e, space0_around_ee, space0_before_e,
@@ -233,12 +233,41 @@ fn loc_term<'a>() -> impl Parser<'a, Loc<Expr<'a>>, EExpr<'a>> {
             ),
             zero_or_more(pnc_args()),
         ),
-        |arena, (expr, arg_locs_vec)| {
+        #[allow(clippy::type_complexity)]
+        |arena,
+         (expr, arg_locs_with_suffixes_vec): (
+            Loc<Expr<'a>>,
+            bumpalo::collections::Vec<
+                'a,
+                (
+                    Loc<Collection<'a, &'a Loc<Expr>>>,
+                    Option<Vec<'a, Suffix<'a>>>,
+                ),
+            >,
+        )| {
             let mut e = expr;
-            for args_loc in arg_locs_vec.iter() {
+            let orig_region = e.region;
+            for (args_loc, maybe_suffixes) in arg_locs_with_suffixes_vec.iter() {
+                let value = if matches!(
+                    e,
+                    Loc {
+                        value: Expr::Dbg,
+                        ..
+                    }
+                ) {
+                    Expr::Apply(arena.alloc(e), args_loc.value.items, CalledVia::Space)
+                } else if let Some(suffixes) = maybe_suffixes {
+                    apply_expr_access_chain(
+                        arena,
+                        Expr::PncApply(arena.alloc(e), args_loc.value),
+                        suffixes.clone(),
+                    )
+                } else {
+                    Expr::PncApply(arena.alloc(e), args_loc.value)
+                };
                 e = Loc {
-                    value: Expr::Apply(arena.alloc(e), args_loc.value, CalledVia::ParensAndCommas),
+                    value,
-                    region: Region::span_across(&expr.region, &args_loc.region),
+                    region: Region::span_across(&orig_region, &args_loc.region),
                 };
             }
             e
@@ -247,9 +276,16 @@ fn loc_term<'a>() -> impl Parser<'a, Loc<Expr<'a>>, EExpr<'a>> {
     .trace("term")
 }
 
-fn pnc_args<'a>() -> impl Parser<'a, Loc<&'a [&'a Loc<Expr<'a>>]>, EExpr<'a>> {
+fn pnc_args<'a>() -> impl Parser<
+    'a,
+    (
+        Loc<Collection<'a, &'a Loc<Expr<'a>>>>,
+        Option<Vec<'a, Suffix<'a>>>,
+    ),
+    EExpr<'a>,
+> {
     |arena: &'a Bump, state: State<'a>, min_indent: u32| {
-        map_with_arena(
+        let args_then_suffixes = and(
             specialize_err(
                 EExpr::InParens,
                 loc(collection_trailing_sep_e(
@@ -260,32 +296,23 @@ fn pnc_args<'a>() -> impl Parser<'a, Loc<&'a [&'a Loc<Expr<'a>>]>, EExpr<'a>> {
                     Expr::SpaceBefore,
                 )),
             ),
-            |arena, arg_loc: Loc<Collection<'a, Loc<Expr<'a>>>>| {
+            optional(record_field_access_chain()),
-                let mut args_vec = Vec::new_in(arena);
+        );
-                let args_len = arg_loc.value.items.len();
+        map_with_arena(
-                for (i, arg) in arg_loc.value.items.iter().enumerate() {
+            args_then_suffixes,
-                    if i == (args_len - 1) {
+            |arena: &'a Bump,
-                        let last_comments = arg_loc.value.final_comments();
+             (loc_args_coll, maybe_suffixes): (
-                        if !last_comments.is_empty() {
+                Loc<Collection<'a, Loc<Expr<'a>>>>,
-                            let sa = Expr::SpaceAfter(arena.alloc(arg.value), last_comments);
+                Option<Vec<'a, Suffix<'a>>>,
-                            let arg_with_spaces: &Loc<Expr<'a>> = arena.alloc(Loc {
+            )| {
-                                value: sa,
+                let args = loc_args_coll.value.ptrify_items(arena);
-                                region: arg.region,
+                (
-                            });
-                            args_vec.push(arg_with_spaces);
-                        } else {
-                            let a: &Loc<Expr<'a>> = arena.alloc(arg);
-                            args_vec.push(a);
-                        }
-                    } else {
-                        let a: &Loc<Expr<'a>> = arena.alloc(arg);
-                        args_vec.push(a);
-                    }
-                }
                     Loc {
-                    value: args_vec.into_bump_slice(),
+                        region: loc_args_coll.region,
-                    region: arg_loc.region,
+                        value: args,
-                }
+                    },
+                    maybe_suffixes,
+                )
             },
         )
         .parse(arena, state, min_indent)
@@ -2117,7 +2144,7 @@ fn expr_to_pattern_help<'a>(arena: &'a Bump, expr: &Expr<'a>) -> Result<Pattern<
         Expr::Underscore(opt_name) => Pattern::Underscore(opt_name),
         Expr::Tag(value) => Pattern::Tag(value),
         Expr::OpaqueRef(value) => Pattern::OpaqueRef(value),
-        Expr::Apply(loc_val, loc_args, called_via) => {
+        Expr::Apply(loc_val, loc_args, _) => {
             let region = loc_val.region;
             let value = expr_to_pattern_help(arena, &loc_val.value)?;
             let val_pattern = arena.alloc(Loc { region, value });
@@ -2131,18 +2158,22 @@ fn expr_to_pattern_help<'a>(arena: &'a Bump, expr: &Expr<'a>) -> Result<Pattern<
                 arg_patterns.push(Loc { region, value });
             }
 
-            let pattern = Pattern::Apply(
+            let pattern = Pattern::Apply(val_pattern, arg_patterns.into_bump_slice());
-                val_pattern,
-                arg_patterns.into_bump_slice(),
-                if matches!(called_via, CalledVia::ParensAndCommas) {
-                    PatternApplyStyle::ParensAndCommas
-                } else {
-                    PatternApplyStyle::Whitespace
-                },
-            );
 
             pattern
         }
+        Expr::PncApply(loc_val, args) => {
+            let region = loc_val.region;
+            let value = expr_to_pattern_help(arena, &loc_val.value)?;
+            let val_pattern = arena.alloc(Loc { region, value });
+            let pattern_args = args.map_items_result(arena, |arg| {
+                let region = arg.region;
+                let value = expr_to_pattern_help(arena, &arg.value)?;
+                Ok(Loc { region, value })
+            })?;
+
+            Pattern::PncApply(val_pattern, pattern_args)
+        }
 
         Expr::Try => Pattern::Identifier { ident: "try" },
 
@@ -3143,6 +3174,31 @@ fn stmts_to_defs<'a>(
 
                         last_expr = Some(Loc::at(sp_stmt.item.region, e));
 
+                        // don't re-process the rest of the statements; they got consumed by the dbg expr
+                        break;
+                    } else if let Expr::PncApply(
+                        Loc {
+                            value: Expr::Dbg, ..
+                        },
+                        args,
+                    ) = e
+                    {
+                        let condition = &args.items[0];
+                        let rest = stmts_to_expr(&stmts[i + 1..], arena)?;
+                        let e = Expr::DbgStmt {
+                            first: condition,
+                            extra_args: &args.items[1..],
+                            continuation: arena.alloc(rest),
+                        };
+
+                        let e = if sp_stmt.before.is_empty() {
+                            e
+                        } else {
+                            arena.alloc(e).before(sp_stmt.before)
+                        };
+
+                        last_expr = Some(Loc::at(sp_stmt.item.region, e));
+
                         // don't re-process the rest of the statements; they got consumed by the dbg expr
                         break;
                     } else {
@@ -3313,7 +3369,8 @@ fn starts_with_spaces_conservative(value: &Pattern<'_>) -> bool {
         | Pattern::ListRest(_)
         | Pattern::OpaqueRef(_) => false,
         Pattern::As(left, _) => starts_with_spaces_conservative(&left.value),
-        Pattern::Apply(left, _, _) => starts_with_spaces_conservative(&left.value),
+        Pattern::Apply(left, _) => starts_with_spaces_conservative(&left.value),
+        Pattern::PncApply(left, _) => starts_with_spaces_conservative(&left.value),
         Pattern::RecordDestructure(_) => false,
         Pattern::RequiredField(_, _) | Pattern::OptionalField(_, _) => false,
         Pattern::SpaceBefore(_, _) => true,
@@ -3329,7 +3386,6 @@ fn header_to_pat<'a>(arena: &'a Bump, header: TypeHeader<'a>) -> Pattern<'a> {
         Pattern::Apply(
             arena.alloc(Loc::at(header.name.region, Pattern::Tag(header.name.value))),
             header.vars,
-            PatternApplyStyle::Whitespace,
         )
     }
 }
@@ -3380,8 +3436,8 @@ fn pat_ends_with_spaces_conservative(pat: &Pattern<'_>) -> bool {
         | Pattern::ListRest(_)
         | Pattern::As(_, _)
         | Pattern::OpaqueRef(_)
-        | Pattern::Apply(_, _, PatternApplyStyle::ParensAndCommas) => false,
+        | Pattern::PncApply(_, _) => false,
-        Pattern::Apply(_, args, _) => args
+        Pattern::Apply(_, args) => args
             .last()
             .map_or(false, |a| pat_ends_with_spaces_conservative(&a.value)),
         Pattern::RecordDestructure(_) => false,
@@ -3403,7 +3459,7 @@ pub fn join_alias_to_body<'a>(
     body_expr: &'a Loc<Expr<'a>>,
 ) -> ValueDef<'a> {
     let loc_name = arena.alloc(header.name.map(|x| Pattern::Tag(x)));
-    let ann_pattern = Pattern::Apply(loc_name, header.vars, PatternApplyStyle::Whitespace);
+    let ann_pattern = Pattern::Apply(loc_name, header.vars);
 
     let vars_region = Region::across_all(header.vars.iter().map(|v| &v.region));
     let region_ann_pattern = Region::span_across(&loc_name.region, &vars_region);

crates/compiler/parse/src/normalize.rs

@@ -737,8 +737,13 @@ impl<'a> Normalize<'a> for Expr<'a> {
                 arena.alloc(a.normalize(arena)),
                 b.map(|loc_b| &*arena.alloc(loc_b.normalize(arena))),
             ),
-            Expr::Apply(a, b, c) => {
+            Expr::Apply(a, b, called_via) => Expr::Apply(
-                Expr::Apply(arena.alloc(a.normalize(arena)), b.normalize(arena), c)
+                arena.alloc(a.normalize(arena)),
+                b.normalize(arena),
+                called_via,
+            ),
+            Expr::PncApply(a, b) => {
+                Expr::PncApply(arena.alloc(a.normalize(arena)), b.normalize(arena))
             }
             Expr::BinOps(a, b) => Expr::BinOps(a.normalize(arena), arena.alloc(b.normalize(arena))),
             Expr::UnaryOp(a, b) => {
@@ -835,6 +840,30 @@ fn fold_defs<'a>(
                             arena.alloc(Loc::at_zero(new_final)),
                         );
                     }
+                    ValueDef::Stmt(&Loc {
+                        value:
+                            Expr::PncApply(
+                                &Loc {
+                                    value: Expr::Dbg, ..
+                                },
+                                args,
+                            ),
+                        ..
+                    }) => {
+                        let rest = fold_defs(arena, defs, final_expr);
+                        let new_final = Expr::DbgStmt {
+                            first: args.items[0],
+                            extra_args: &args.items[1..],
+                            continuation: arena.alloc(Loc::at_zero(rest)),
+                        };
+                        if new_defs.is_empty() {
+                            return new_final;
+                        }
+                        return Expr::Defs(
+                            arena.alloc(new_defs),
+                            arena.alloc(Loc::at_zero(new_final)),
+                        );
+                    }
                     _ => {
                         new_defs.push_value_def(vd, Region::zero(), &[], &[]);
                     }
@@ -879,11 +908,13 @@ impl<'a> Normalize<'a> for Pattern<'a> {
             Pattern::Identifier { ident } => Pattern::Identifier { ident },
             Pattern::Tag(a) => Pattern::Tag(a),
             Pattern::OpaqueRef(a) => Pattern::OpaqueRef(a),
-            Pattern::Apply(a, b, c) => Pattern::Apply(
+            Pattern::Apply(a, b) => Pattern::Apply(
                 arena.alloc(a.normalize(arena)),
                 arena.alloc(b.normalize(arena)),
-                c,
             ),
+            Pattern::PncApply(a, b) => {
+                Pattern::PncApply(arena.alloc(a.normalize(arena)), b.normalize(arena))
+            }
             Pattern::RecordDestructure(a) => Pattern::RecordDestructure(a.normalize(arena)),
             Pattern::RequiredField(a, b) => {
                 Pattern::RequiredField(a, arena.alloc(b.normalize(arena)))

crates/compiler/parse/src/pattern.rs

@@ -1,6 +1,4 @@
-use crate::ast::{
+use crate::ast::{Collection, ExtractSpaces, Implements, Pattern, PatternAs, Spaceable};
-    Collection, ExtractSpaces, Implements, Pattern, PatternApplyStyle, PatternAs, Spaceable,
-};
 use crate::blankspace::{space0_before_optional_after, space0_e, spaces, spaces_before};
 use crate::ident::{lowercase_ident, parse_ident, Accessor, Ident};
 use crate::keyword;
@@ -337,35 +335,30 @@ fn loc_ident_pattern_help<'a>(
         let (_, loc_ident, state) = specialize_err(|_, pos| EPattern::Start(pos), loc(parse_ident))
             .parse(arena, state, min_indent)?;
 
-        let commas_and_paren_args_help = map_with_arena(
+        enum ArgType<'a> {
-            collection_trailing_sep_e(
+            PncArgs(Loc<Collection<'a, Loc<Pattern<'a>>>>),
+            WhitespaceArgs(&'a [Loc<Pattern<'a>>]),
+        }
+
+        let commas_and_paren_args_help = map(
+            loc(collection_trailing_sep_e(
                 byte(b'(', EPattern::ParenStart),
                 loc_tag_pattern_arg(false),
                 byte(b',', EPattern::NotAPattern),
                 byte(b')', EPattern::ParenEnd),
                 Pattern::SpaceBefore,
-            ),
+            )),
-            |arena, args| {
+            ArgType::PncArgs,
-                let mut args_vec = Vec::new_in(arena);
-                for arg in args.iter() {
-                    let a: &Loc<Pattern<'a>> = arena.alloc(arg);
-                    args_vec.push(*a);
-                }
-                (
-                    args_vec.into_bump_slice(),
-                    PatternApplyStyle::ParensAndCommas,
-                )
-            },
         );
 
         let whitespace_args =
             map_with_arena(loc_type_def_tag_pattern_args_help(), |arena, args| {
-                let mut args_vec = Vec::new_in(arena);
+                let mut args_vec = Vec::with_capacity_in(args.len(), arena);
                 for arg in args.iter() {
                     let a: &Loc<Pattern<'a>> = arena.alloc(arg);
                     args_vec.push(*a);
                 }
-                (args_vec.into_bump_slice(), PatternApplyStyle::Whitespace)
+                ArgType::WhitespaceArgs(args_vec.into_bump_slice())
             });
 
         match loc_ident.value {
@@ -376,7 +369,7 @@ fn loc_ident_pattern_help<'a>(
                 };
 
                 // Make sure `Foo Bar 1` is parsed as `Foo (Bar) 1`, and not `Foo (Bar 1)`
-                let (_, (args, style), state) = if can_have_arguments {
+                let (_, arg_type, state) = if can_have_arguments {
                     one_of!(commas_and_paren_args_help, whitespace_args)
                         .parse(arena, state, min_indent)?
                 } else {
@@ -386,9 +379,15 @@ fn loc_ident_pattern_help<'a>(
                         Err((MadeProgress, e)) => return Err((MadeProgress, e)),
                     }
                 };
-
+                match arg_type {
+                    ArgType::PncArgs(args) => {
+                        let pnc_args = args.value;
+                        let value = Pattern::PncApply(&*arena.alloc(loc_tag), pnc_args);
+                        let region = Region::span_across(&loc_ident.region, &args.region);
+                        Ok((MadeProgress, Loc { region, value }, state))
+                    }
+                    ArgType::WhitespaceArgs(args) => {
                         let loc_args: &[Loc<Pattern<'_>>] = { args };
-
                         if loc_args.is_empty() {
                             Ok((MadeProgress, loc_tag, state))
                         } else {
@@ -396,11 +395,13 @@ fn loc_ident_pattern_help<'a>(
                                 std::iter::once(&loc_ident.region)
                                     .chain(loc_args.iter().map(|loc_arg| &loc_arg.region)),
                             );
-                    let value = Pattern::Apply(&*arena.alloc(loc_tag), loc_args, style);
+                            let value = Pattern::Apply(&*arena.alloc(loc_tag), loc_args);
 
                             Ok((MadeProgress, Loc { region, value }, state))
                         }
                     }
+                }
+            }
             Ident::OpaqueRef(name) => {
                 let loc_pat = Loc {
                     region: loc_ident.region,
@@ -408,15 +409,25 @@ fn loc_ident_pattern_help<'a>(
                 };
 
                 // Make sure `@Foo Bar 1` is parsed as `@Foo (Bar) 1`, and not `@Foo (Bar 1)`
-                let (_, (args, style), state) = if can_have_arguments {
+                let (_, arg_type, state) = if can_have_arguments {
                     one_of!(commas_and_paren_args_help, whitespace_args)
                         .parse(arena, state, min_indent)?
                 } else {
-                    commas_and_paren_args_help.parse(arena, state, min_indent)?
+                    match commas_and_paren_args_help.parse(arena, state.clone(), min_indent) {
+                        Ok((_, res, new_state)) => (MadeProgress, res, new_state),
+                        Err((NoProgress, _)) => return Ok((MadeProgress, loc_pat, state)),
+                        Err((MadeProgress, e)) => return Err((MadeProgress, e)),
+                    }
                 };
-
+                match arg_type {
+                    ArgType::PncArgs(args) => {
+                        let pnc_args = args.value;
+                        let value = Pattern::PncApply(&*arena.alloc(loc_pat), pnc_args);
+                        let region = Region::span_across(&loc_ident.region, &args.region);
+                        Ok((MadeProgress, Loc { region, value }, state))
+                    }
+                    ArgType::WhitespaceArgs(args) => {
                         let loc_args: &[Loc<Pattern<'_>>] = { args };
-
                         if loc_args.is_empty() {
                             Ok((MadeProgress, loc_pat, state))
                         } else {
@@ -424,11 +435,13 @@ fn loc_ident_pattern_help<'a>(
                                 std::iter::once(&loc_ident.region)
                                     .chain(loc_args.iter().map(|loc_arg| &loc_arg.region)),
                             );
-                    let value = Pattern::Apply(&*arena.alloc(loc_pat), loc_args, style);
+                            let value = Pattern::Apply(&*arena.alloc(loc_pat), loc_args);
 
                             Ok((MadeProgress, Loc { region, value }, state))
                         }
                     }
+                }
+            }
             Ident::Access {
                 module_name, parts, ..
             } => {
@@ -683,7 +696,7 @@ mod test_parse_pattern {
             region: new_region(3, 4),
         }];
         let expected = Loc {
-            value: Pattern::Apply(&expected_tag, &expected_args, PatternApplyStyle::Whitespace),
+            value: Pattern::Apply(&expected_tag, &expected_args),
             region: new_region(0, 4),
         };
         assert_eq!(format!("{res:#?}"), format!("{expected:#?}"));
@@ -699,17 +712,13 @@ mod test_parse_pattern {
             value: Pattern::Tag("Ok"),
             region: new_region(0, 2),
         };
-        let expected_args = [Loc {
+        let expected_args = Collection::with_items(arena.alloc([Loc {
             value: Pattern::Identifier { ident: "a" },
             region: new_region(3, 4),
-        }];
+        }]));
         let expected = Loc {
-            value: Pattern::Apply(
+            value: Pattern::PncApply(&expected_tag, expected_args),
-                &expected_tag,
+            region: new_region(0, 5),
-                &expected_args,
-                PatternApplyStyle::ParensAndCommas,
-            ),
-            region: new_region(0, 4),
         };
         assert_eq!(format!("{res:#?}"), format!("{expected:#?}"));
     }

crates/compiler/problem/src/can.rs

@@ -512,13 +512,14 @@ impl Problem {
             | Problem::ReturnAtEndOfFunction { region }
             | Problem::UnboundTypeVarsInAs(region)
             | Problem::UnsuffixedEffectfulRecordField(region)
-            | Problem::SuffixedPureRecordField(region) => Some(*region),
+            | Problem::SuffixedPureRecordField(region)
+            | Problem::StmtAfterExpr(region) => Some(*region),
+
             Problem::RuntimeError(RuntimeError::CircularDef(cycle_entries))
             | Problem::BadRecursion(cycle_entries) => {
                 cycle_entries.first().map(|entry| entry.expr_region)
             }
 
-            Problem::StmtAfterExpr(region) => Some(*region),
             Problem::RuntimeError(RuntimeError::UnresolvedTypeVar)
             | Problem::RuntimeError(RuntimeError::ErroneousType)
             | Problem::RuntimeError(RuntimeError::NonExhaustivePattern)

crates/compiler/test_syntax/src/test_helpers.rs

@@ -23,7 +23,7 @@ use roc_parse::{
 };
 use roc_region::all::Loc;
 use roc_region::all::Region;
-use roc_test_utils::assert_multiline_str_eq;
+use roc_test_utils::{assert_multiline_str_eq, pretty_compare_string};
 use roc_types::{
     subs::{VarStore, Variable},
     types::{AliasVar, Type},
@@ -392,6 +392,10 @@ impl<'a> Input<'a> {
             // I don't have the patience to debug this right now, so let's leave it for another day...
             // TODO: fix PartialEq impl on ast types
             if format!("{ast_normalized:?}") != format!("{reparsed_ast_normalized:?}") {
+                pretty_compare_string(
+                    format!("{ast_normalized:#?}").as_str(),
+                    format!("{reparsed_ast_normalized:#?}").as_str(),
+                );
                 panic!(
                     "Formatting bug; formatting didn't reparse to the same AST (after removing spaces)\n\n\
                     * * * Source code before formatting:\n{}\n\n\
@@ -411,6 +415,10 @@ impl<'a> Input<'a> {
             let reformatted = reparsed_ast.format(flags);
 
             if output != reformatted {
+                pretty_compare_string(
+                    format!("{actual:#?}").as_str(),
+                    format!("{reparsed_ast:#?}").as_str(),
+                );
                 eprintln!("Formatting bug; formatting is not stable.\nOriginal code:\n{}\n\nFormatted code:\n{}\n\nAST:\n{:#?}\n\nReparsed AST:\n{:#?}\n\n",
                     self.as_str(),
                     output.as_ref().as_str(),

crates/compiler/test_syntax/tests/snapshots/pass/annotated_empty_record_destructure.expr.result-ast

@@ -21,7 +21,6 @@
                         "E",
                     ),
                     [],
-                    Whitespace,
                 ),
                 ann_type: @2-3 Apply(
                     "",

crates/compiler/test_syntax/tests/snapshots/pass/annotated_tag_destructure.expr.result-ast

@@ -26,7 +26,6 @@
                                 ident: "x",
                             },
                         ],
-                        Whitespace,
                     ),
                     ann_type: @11-25 TagUnion {
                         ext: None,
@@ -55,7 +54,6 @@
                                 ident: "x",
                             },
                         ],
-                        Whitespace,
                     ),
                     body_expr: @37-46 Apply(
                         @37-43 Tag(

crates/compiler/test_syntax/tests/snapshots/pass/apply_tag_pnc.expr.result-ast

@@ -1,5 +1,5 @@
 @0-12 SpaceAfter(
-    Apply(
+    PncApply(
         @0-4 Tag(
             "Whee",
         ),
@@ -11,7 +11,6 @@
                 "34",
             ),
         ],
-        ParensAndCommas,
     ),
     [
         Newline,

crates/compiler/test_syntax/tests/snapshots/pass/apply_tag_single_arg_pnc.pattern.result-ast

@@ -1,5 +1,5 @@
-@0-4 SpaceAfter(
+@0-5 SpaceAfter(
-    Apply(
+    PncApply(
         @0-2 Tag(
             "Ok",
         ),
@@ -8,7 +8,6 @@
                 ident: "a",
             },
         ],
-        ParensAndCommas,
     ),
     [
         Newline,

crates/compiler/test_syntax/tests/snapshots/pass/apply_tag_single_arg_whitespace.pattern.result-ast

@@ -8,7 +8,6 @@
                 ident: "a",
             },
         ],
-        Whitespace,
     ),
     [
         Newline,

crates/compiler/test_syntax/tests/snapshots/pass/apply_two_args_pnc.expr.result-ast

@@ -1,5 +1,5 @@
 @0-13 SpaceAfter(
-    Apply(
+    PncApply(
         @0-4 Var {
             module_name: "",
             ident: "whee",
@@ -12,7 +12,6 @@
                 "34",
             ),
         ],
-        ParensAndCommas,
     ),
     [
         Newline,

crates/compiler/test_syntax/tests/snapshots/pass/arg_pattern_as.expr.result-ast

@@ -27,7 +27,6 @@
                             ident: "inner",
                         },
                     ],
-                    Whitespace,
                 ),
                 PatternAs {
                     spaces_before: [],

crates/compiler/test_syntax/tests/snapshots/pass/closure_complex_pattern_indent_issue.expr.result-ast

@@ -38,7 +38,6 @@
                         },
                     ),
                 ],
-                Whitespace,
             ),
         ],
         @17-18 SpaceBefore(

crates/compiler/test_syntax/tests/snapshots/pass/closure_parens_double_newlines.expr.result-ast

@@ -1,7 +1,7 @@
 @0-13 SpaceAfter(
     Closure(
         [
-            @1-5 Apply(
+            @1-9 PncApply(
                 @1-2 Tag(
                     "L",
                 ),
@@ -20,7 +20,6 @@
                         ],
                     ),
                 ],
-                ParensAndCommas,
             ),
         ],
         @11-13 Num(

crates/compiler/test_syntax/tests/snapshots/pass/comment_after_whitespace_apply_arg_inside_pnc_apply.expr.result-ast

@@ -1,5 +1,5 @@
 @0-44 SpaceAfter(
-    Apply(
+    PncApply(
         @0-2 Tag(
             "PP",
         ),
@@ -10,7 +10,7 @@
                         "P",
                     ),
                     [
-                        @4-42 Apply(
+                        @4-42 PncApply(
                             @4-6 OpaqueRef(
                                 "@P",
                             ),
@@ -22,13 +22,13 @@
                                         ),
                                         [
                                             @9-24 SpaceBefore(
-                                                Apply(
+                                                PncApply(
                                                     @9-10 Tag(
                                                         "P",
                                                     ),
                                                     [
                                                         @11-22 SpaceAfter(
-                                                            Apply(
+                                                            PncApply(
                                                                 @11-14 Tag(
                                                                     "PPP",
                                                                 ),
@@ -55,21 +55,19 @@
                                                                         ],
                                                                     ),
                                                                 ],
-                                                                ParensAndCommas,
                                                             ),
                                                             [
                                                                 Newline,
                                                             ],
                                                         ),
                                                     ],
-                                                    ParensAndCommas,
                                                 ),
                                                 [
                                                     Newline,
                                                 ],
                                             ),
                                             @25-40 SpaceBefore(
-                                                Apply(
+                                                PncApply(
                                                     @25-27 Tag(
                                                         "PP",
                                                     ),
@@ -86,7 +84,6 @@
                                                             ],
                                                         ),
                                                     ],
-                                                    ParensAndCommas,
                                                 ),
                                                 [
                                                     Newline,
@@ -100,7 +97,6 @@
                                     ],
                                 ),
                             ],
-                            ParensAndCommas,
                         ),
                     ],
                     Space,
@@ -110,7 +106,6 @@
                 ],
             ),
         ],
-        ParensAndCommas,
     ),
     [
         Newline,

crates/compiler/test_syntax/tests/snapshots/pass/comment_in_closure_pat.expr.result-ast

@@ -16,7 +16,6 @@
                     ],
                 ),
             ],
-            Whitespace,
         ),
     ],
     @8-10 UnaryOp(

crates/compiler/test_syntax/tests/snapshots/pass/comment_in_closure_pat_apply.expr.result-ast

@@ -19,7 +19,6 @@
                     ],
                 ),
             ],
-            Whitespace,
         ),
     ],
     @10-12 Var {

crates/compiler/test_syntax/tests/snapshots/pass/comment_indent_in_parens.expr.formatted.roc

@@ -1,4 +1,5 @@
-1(0) #
+1(
+    0, #
     #
- : gi
+) : gi
 M

crates/compiler/test_syntax/tests/snapshots/pass/comment_indent_in_parens.expr.result-ast

@@ -16,7 +16,7 @@
         type_defs: [],
         value_defs: [
             Annotation(
-                @0-10 Apply(
+                @0-10 PncApply(
                     @0-1 NumLiteral(
                         "1",
                     ),
@@ -35,7 +35,6 @@
                             ],
                         ),
                     ],
-                    ParensAndCommas,
                 ),
                 @11-13 BoundVariable(
                     "gi",

crates/compiler/test_syntax/tests/snapshots/pass/crazy_annotation_left.expr.formatted.roc

@@ -1,5 +1,7 @@
 1(
     0( #
-        0,),)
+        0,
+    ),
+)
     f : f
 t

crates/compiler/test_syntax/tests/snapshots/pass/crazy_annotation_left.expr.result-ast

@@ -18,13 +18,13 @@
             value_defs: [
                 Annotation(
                     @0-12 Apply(
-                        @0-12 Apply(
+                        @0-12 PncApply(
                             @0-1 NumLiteral(
                                 "1",
                             ),
                             [
                                 @2-11 SpaceAfter(
-                                    Apply(
+                                    PncApply(
                                         @3-4 NumLiteral(
                                             "0",
                                         ),
@@ -40,21 +40,18 @@
                                                 ],
                                             ),
                                         ],
-                                        ParensAndCommas,
                                     ),
                                     [
                                         Newline,
                                     ],
                                 ),
                             ],
-                            ParensAndCommas,
                         ),
                         [
                             @12-13 Identifier {
                                 ident: "f",
                             },
                         ],
-                        Whitespace,
                     ),
                     @14-15 BoundVariable(
                         "f",

crates/compiler/test_syntax/tests/snapshots/pass/crazy_annotation_left2.expr.formatted.roc

@@ -1,7 +1,9 @@
 1(
-    ts(0),)
+    ts(
+        0,
 
         #
-
+    ),
+)
     f : i7f
 e

crates/compiler/test_syntax/tests/snapshots/pass/crazy_annotation_left2.expr.result-ast

@@ -17,13 +17,13 @@
         value_defs: [
             Annotation(
                 @0-15 Apply(
-                    @0-15 Apply(
+                    @0-15 PncApply(
                         @0-1 NumLiteral(
                             "1",
                         ),
                         [
                             @2-13 SpaceAfter(
-                                Apply(
+                                PncApply(
                                     @2-4 Identifier {
                                         ident: "ts",
                                     },
@@ -41,21 +41,18 @@
                                             ],
                                         ),
                                     ],
-                                    ParensAndCommas,
                                 ),
                                 [
                                     Newline,
                                 ],
                             ),
                         ],
-                        ParensAndCommas,
                     ),
                     [
                         @15-16 Identifier {
                             ident: "f",
                         },
                     ],
-                    Whitespace,
                 ),
                 @17-20 BoundVariable(
                     "i7f",

crates/compiler/test_syntax/tests/snapshots/pass/crazy_pat_ann.expr.result-ast

@@ -34,7 +34,6 @@
                                 ident: "f",
                             },
                         ],
-                        Whitespace,
                     ),
                     @14-15 BoundVariable(
                         "f",

crates/compiler/test_syntax/tests/snapshots/pass/destructure_tag_assignment.expr.result-ast

@@ -26,7 +26,6 @@
                                 ident: "str",
                             },
                         ],
-                        Whitespace,
                     ),
                     @12-36 Apply(
                         @12-17 Tag(

crates/compiler/test_syntax/tests/snapshots/pass/double_parens_comment_tuple_pat.expr.result-ast

@@ -35,7 +35,6 @@
                                         ident: "e",
                                     },
                                 ],
-                                Whitespace,
                             ),
                             @8-14 Apply(
                                 @9-10 SpaceAfter(
@@ -53,7 +52,6 @@
                                         ident: "p",
                                     },
                                 ],
-                                Whitespace,
                             ),
                         ],
                     ),

crates/compiler/test_syntax/tests/snapshots/pass/implements_in_pat_after_comment.expr.result-ast

@@ -33,7 +33,6 @@
                                 ],
                             ),
                         ],
-                        Whitespace,
                     ),
                     @15-16 BoundVariable(
                         "s",

crates/compiler/test_syntax/tests/snapshots/pass/long_complex_application_with_pnc.expr.formatted.roc

@@ -1,8 +1,10 @@
 combine(
     mix(vodka, gin),
-    Juices({
+    Juices(
+        {
             color: Colors.orange,
             flavor: Flavors.orange,
             amount: 1 + 2,
-    }),
+        },
+    ),
 )

crates/compiler/test_syntax/tests/snapshots/pass/long_complex_application_with_pnc.expr.result-ast

@@ -1,11 +1,11 @@
 @0-109 SpaceAfter(
-    Apply(
+    PncApply(
         @0-7 Var {
             module_name: "",
             ident: "combine",
         },
         [
-            @8-23 Apply(
+            @8-23 PncApply(
                 @8-11 Var {
                     module_name: "",
                     ident: "mix",
@@ -20,9 +20,8 @@
                         ident: "gin",
                     },
                 ],
-                ParensAndCommas,
             ),
-            @25-108 Apply(
+            @25-108 PncApply(
                 @25-31 Tag(
                     "Juices",
                 ),
@@ -85,10 +84,8 @@
                         ],
                     ),
                 ],
-                ParensAndCommas,
             ),
         ],
-        ParensAndCommas,
     ),
     [
         Newline,

crates/compiler/test_syntax/tests/snapshots/pass/mega_parens_pat.expr.formatted.roc

@@ -1,6 +1,8 @@
 1(
     0 #
-        f,)(
+        f,
+)(
     0 #
-        f,) : f
+        f,
+) : f
 e

crates/compiler/test_syntax/tests/snapshots/pass/mega_parens_pat.expr.result-ast

@@ -17,8 +17,8 @@
             type_defs: [],
             value_defs: [
                 Annotation(
-                    @0-17 Apply(
+                    @0-17 PncApply(
-                        @0-9 Apply(
+                        @0-9 PncApply(
                             @0-1 NumLiteral(
                                 "1",
                             ),
@@ -39,10 +39,8 @@
                                             ident: "f",
                                         },
                                     ],
-                                    Whitespace,
                                 ),
                             ],
-                            ParensAndCommas,
                         ),
                         [
                             @10-16 Apply(
@@ -61,10 +59,8 @@
                                         ident: "f",
                                     },
                                 ],
-                                Whitespace,
                             ),
                         ],
-                        ParensAndCommas,
                     ),
                     @18-19 BoundVariable(
                         "f",

crates/compiler/test_syntax/tests/snapshots/pass/multiline_apply_equals_multiline_apply.expr.result-ast

@@ -32,7 +32,6 @@
                                     ],
                                 ),
                             ],
-                            Whitespace,
                         ),
                         [
                             Newline,

crates/compiler/test_syntax/tests/snapshots/pass/multiline_str_after_newlines_in_pat.expr.result-ast

@@ -34,7 +34,6 @@
                                 ),
                             ),
                         ],
-                        Whitespace,
                     ),
                     @12-13 Apply(
                         "",

crates/compiler/test_syntax/tests/snapshots/pass/multiline_str_and_str_in_alias.expr.result-ast

@@ -42,14 +42,12 @@
                                     ),
                                 ),
                             ],
-                            Whitespace,
                         ),
                         [
                             @12-13 Identifier {
                                 ident: "f",
                             },
                         ],
-                        Whitespace,
                     ),
                     @14-15 Apply(
                         "",

crates/compiler/test_syntax/tests/snapshots/pass/multiline_str_apply_in_parens_pat.expr.result-ast

@@ -33,10 +33,8 @@
                                         "0",
                                     ),
                                 ],
-                                Whitespace,
                             ),
                         ],
-                        Whitespace,
                     ),
                     @15-16 BoundVariable(
                         "f",

crates/compiler/test_syntax/tests/snapshots/pass/multiline_str_in_pat.expr.result-ast

@@ -36,7 +36,6 @@
                                 "2",
                             ),
                         ],
-                        Whitespace,
                     ),
                     @12-13 Apply(
                         "",

crates/compiler/test_syntax/tests/snapshots/pass/neg_nested_parens.expr.result-ast

@@ -1,6 +1,6 @@
 @0-9 UnaryOp(
     @2-8 ParensAround(
-        Apply(
+        PncApply(
             @2-3 Num(
                 "0",
             ),
@@ -23,7 +23,6 @@
                     Space,
                 ),
             ],
-            ParensAndCommas,
         ),
     ),
     @0-1 Negate,

crates/compiler/test_syntax/tests/snapshots/pass/nested_list_comment_in_closure_arg.expr.result-ast

@@ -32,7 +32,6 @@
                     ],
                 ),
             ],
-            Whitespace,
         ),
     ],
     @14-15 Var {

crates/compiler/test_syntax/tests/snapshots/pass/nested_parens_in_pattern.expr.result-ast

@@ -25,7 +25,6 @@
                             ident: "x",
                         },
                     ],
-                    Whitespace,
                 ),
                 @7-8 BoundVariable(
                     "i",

crates/compiler/test_syntax/tests/snapshots/pass/nested_when_comment_in_pat.expr.result-ast

@@ -23,7 +23,6 @@
                                     ],
                                 ),
                             ],
-                            Whitespace,
                         ),
                         [
                             Newline,

crates/compiler/test_syntax/tests/snapshots/pass/opaque_destructure_first_item_in_body.expr.result-ast

@@ -26,7 +26,6 @@
                                 ident: "it",
                             },
                         ],
-                        Whitespace,
                     ),
                     @12-22 Apply(
                         @12-14 Var {

crates/compiler/test_syntax/tests/snapshots/pass/opaque_reference_pattern_with_arguments.expr.result-ast

@@ -20,7 +20,6 @@
                                     ident: "m",
                                 },
                             ],
-                            Whitespace,
                         ),
                         [
                             Newline,

crates/compiler/test_syntax/tests/snapshots/pass/parens_in_type_def_apply.expr.result-ast

@@ -28,7 +28,6 @@
                                         ident: "a",
                                     },
                                 ],
-                                Whitespace,
                             ),
                         ],
                     },

crates/compiler/test_syntax/tests/snapshots/pass/pattern_comma_newlines.expr.formatted.roc

@@ -1,3 +1,5 @@
-1(i, p) #
+1(
- : f
+    i,
+    p, #
+) : f
 n

crates/compiler/test_syntax/tests/snapshots/pass/pattern_comma_newlines.expr.result-ast

@@ -16,7 +16,7 @@
         type_defs: [],
         value_defs: [
             Annotation(
-                @0-8 Apply(
+                @0-8 PncApply(
                     @0-1 NumLiteral(
                         "1",
                     ),
@@ -35,7 +35,6 @@
                             ],
                         ),
                     ],
-                    ParensAndCommas,
                 ),
                 @9-10 BoundVariable(
                     "f",

crates/compiler/test_syntax/tests/snapshots/pass/pattern_record_apply_comment.expr.result-ast

@@ -37,7 +37,6 @@
                                 ],
                             ),
                         ],
-                        Whitespace,
                     ),
                     @7-8 BoundVariable(
                         "s",

crates/compiler/test_syntax/tests/snapshots/pass/pattern_with_as_parens.expr.result-ast

@@ -23,7 +23,6 @@
                                     },
                                 ),
                             ],
-                            Whitespace,
                         ),
                         [
                             Newline,

crates/compiler/test_syntax/tests/snapshots/pass/pattern_with_space_in_parens.expr.result-ast

@@ -43,13 +43,11 @@
                                             ident: "ry",
                                         },
                                     ],
-                                    Whitespace,
                                 ),
                                 @47-48 Underscore(
                                     "",
                                 ),
                             ],
-                            Whitespace,
                         ),
                         [
                             Newline,

crates/compiler/test_syntax/tests/snapshots/pass/quotes_in_parens_in_pat.expr.result-ast

@@ -32,7 +32,6 @@
                                         ),
                                     ),
                                 ],
-                                Whitespace,
                             ),
                         ],
                     },

crates/compiler/test_syntax/tests/snapshots/pass/repr_7342.expr.result-ast

@@ -37,7 +37,6 @@
                                     ident: "a",
                                 },
                             ],
-                            Whitespace,
                         ),
                         @10-11 BoundVariable(
                             "t",

crates/compiler/test_syntax/tests/snapshots/pass/repr_7346.expr.result-ast

@@ -45,7 +45,6 @@
                                                             "K",
                                                         ),
                                                     ],
-                                                    Whitespace,
                                                 ),
                                                 [
                                                     LineComment(

crates/compiler/test_syntax/tests/snapshots/pass/tag_destructure_bang.expr.result-ast

@@ -29,7 +29,6 @@
                                 ident: "code",
                             },
                         ],
-                        Whitespace,
                     ),
                     @30-33 Var {
                         module_name: "",

crates/compiler/test_syntax/tests/snapshots/pass/tag_destructure_bang_no_space.expr.result-ast

@@ -29,7 +29,6 @@
                                 ident: "code",
                             },
                         ],
-                        Whitespace,
                     ),
                     @29-32 Var {
                         module_name: "",

crates/compiler/test_syntax/tests/snapshots/pass/triple_paren_pat_ann.expr.result-ast

@@ -18,12 +18,12 @@
             value_defs: [
                 Annotation(
                     @0-10 Apply(
-                        @0-10 Apply(
+                        @0-10 PncApply(
                             @0-1 NumLiteral(
                                 "1",
                             ),
                             [
-                                @2-9 Apply(
+                                @2-9 PncApply(
                                     @3-4 NumLiteral(
                                         "0",
                                     ),
@@ -37,17 +37,14 @@
                                             ],
                                         ),
                                     ],
-                                    ParensAndCommas,
                                 ),
                             ],
-                            ParensAndCommas,
                         ),
                         [
                             @10-11 Identifier {
                                 ident: "f",
                             },
                         ],
-                        Whitespace,
                     ),
                     @12-13 BoundVariable(
                         "f",

crates/compiler/test_syntax/tests/snapshots/pass/triple_quote_craziness.expr.result-ast

@@ -28,7 +28,6 @@
                                 ),
                             ),
                         ],
-                        Whitespace,
                     ),
                     @8-15 Apply(
                         @8-9 Var {

crates/compiler/test_syntax/tests/snapshots/pass/underscore_in_assignment_pattern.expr.result-ast

@@ -50,7 +50,6 @@
                                 "",
                             ),
                         ],
-                        Whitespace,
                     ),
                     @11-19 Apply(
                         @11-15 Tag(
@@ -80,7 +79,6 @@
                                 ident: "y",
                             },
                         ],
-                        Whitespace,
                     ),
                     @31-39 Apply(
                         @31-35 Tag(
@@ -110,7 +108,6 @@
                                 "",
                             ),
                         ],
-                        Whitespace,
                     ),
                     @51-59 Apply(
                         @51-55 Tag(
@@ -164,7 +161,6 @@
                                         "",
                                     ),
                                 ],
-                                Whitespace,
                             ),
                             @90-98 Apply(
                                 @90-94 Tag(
@@ -178,10 +174,8 @@
                                         ident: "y",
                                     },
                                 ],
-                                Whitespace,
                             ),
                         ],
-                        Whitespace,
                     ),
                     @102-128 Apply(
                         @102-106 Tag(

crates/compiler/test_syntax/tests/snapshots/pass/when_result_list.expr.result-ast

@@ -23,7 +23,6 @@
                                 [],
                             ),
                         ],
-                        Whitespace,
                     ),
                     [
                         Newline,

crates/compiler/test_syntax/tests/test_fmt.rs

@@ -3810,6 +3810,16 @@ mod test_fmt {
         ));
     }
 
+    #[test]
+    fn pipe_pnc_application_with_comment_no_args() {
+        expr_formats_same(indoc!(
+            r"
+            combine( # This is a comment
+            )
+            "
+        ));
+    }
+
     #[test]
     fn single_line_nested_application_with_parens() {
         expr_formats_same(indoc!(

crates/language_server/src/analysis/tokens.rs

@@ -694,6 +694,9 @@ impl IterTokens for Loc<Expr<'_>> {
             Expr::Apply(e1, e2, _called_via) => (e1.iter_tokens(arena).into_iter())
                 .chain(e2.iter_tokens(arena))
                 .collect_in(arena),
+            Expr::PncApply(e1, e2) => (e1.iter_tokens(arena).into_iter())
+                .chain(e2.iter_tokens(arena))
+                .collect_in(arena),
             Expr::BinOps(e1, e2) => (e1.iter_tokens(arena).into_iter())
                 .chain(e2.iter_tokens(arena))
                 .collect_in(arena),
@@ -762,7 +765,10 @@ impl IterTokens for Loc<Pattern<'_>> {
             Pattern::Identifier { .. } => onetoken(Token::Variable, region, arena),
             Pattern::Tag(_) => onetoken(Token::Tag, region, arena),
             Pattern::OpaqueRef(_) => onetoken(Token::Type, region, arena),
-            Pattern::Apply(p1, p2, _) => (p1.iter_tokens(arena).into_iter())
+            Pattern::Apply(p1, p2) => (p1.iter_tokens(arena).into_iter())
+                .chain(p2.iter_tokens(arena))
+                .collect_in(arena),
+            Pattern::PncApply(p1, p2) => (p1.iter_tokens(arena).into_iter())
                 .chain(p2.iter_tokens(arena))
                 .collect_in(arena),
             Pattern::RecordDestructure(ps) => ps.iter_tokens(arena),

crates/test_utils/src/lib.rs

@@ -2,6 +2,7 @@
 
 #[doc(hidden)]
 pub use pretty_assertions::assert_eq as _pretty_assert_eq;
+use pretty_assertions::StrComparison;
 
 #[derive(PartialEq, Eq)]
 pub struct DebugAsDisplay<T>(pub T);
@@ -19,6 +20,17 @@ macro_rules! assert_multiline_str_eq {
     };
 }
 
+pub fn pretty_compare_string(a: &str, b: &str) {
+    println!("{}", StrComparison::new(a, b));
+}
+
+#[macro_export]
+macro_rules! print_pretty_string_comparison {
+    ($a:expr, $b:expr) => {
+        $crate::pretty_compare_strings($a, $b)
+    };
+}
+
 /// a very simple implementation of En/DecoderFormatting to be embedded in roc source under test
 ///
 /// - numbers and bools are encoded as 'n' <num> ' '