Add fx to ErrorType

crates/compiler/load/tests/test_reporting.rs

@@ -5419,9 +5419,9 @@ mod test_reporting {
     6│       2 -> 2
                ^^
 
-    Looks like you are trying to define a function. 
+    Looks like you are trying to define a function.
 
-    In Roc, functions are always written as a lambda, like 
+    In Roc, functions are always written as a lambda, like
 
         increment = \n -> n + 1
     "#

crates/compiler/lower_params/src/type_error.rs

@@ -57,8 +57,8 @@ pub fn remove_module_param_arguments(
                 drop_last_argument(expected);
 
                 if let (
-                    ErrorType::Function(found_args, _, _),
+                    ErrorType::Function(found_args, _, _, _),
-                    ErrorType::Function(expected_args, _, _),
+                    ErrorType::Function(expected_args, _, _, _),
                 ) = (found, expected)
                 {
                     if found_args.len() > expected_args.len() {
@@ -194,7 +194,7 @@ fn remove_for_reason(
 
 fn drop_last_argument(err_type: &mut ErrorType) {
     match err_type {
-        ErrorType::Function(arguments, _, _) => {
+        ErrorType::Function(arguments, _, _, _) => {
             arguments.pop();
         }
         // Irrelevant

crates/compiler/types/src/subs.rs

@@ -1,7 +1,7 @@
 #![deny(unsafe_op_in_unsafe_fn)]
 use crate::types::{
-    name_type_var, AbilitySet, AliasKind, ErrorType, ExtImplicitOpenness, Polarity, RecordField,
+    name_type_var, AbilitySet, AliasKind, ErrorFunctionFx, ErrorType, ExtImplicitOpenness,
-    RecordFieldsError, TupleElemsError, TypeExt, Uls,
+    Polarity, RecordField, RecordFieldsError, TupleElemsError, TypeExt, Uls,
 };
 use crate::unification_table::{self, UnificationTable};
 use roc_collections::all::{FnvMap, ImMap, ImSet, MutSet, SendMap};
@@ -4206,7 +4206,7 @@ fn flat_type_to_err_type(
             ErrorType::Type(symbol, arg_types)
         }
 
-        Func(arg_vars, closure_var, ret_var, _fx_var) => {
+        Func(arg_vars, closure_var, ret_var, fx_var) => {
             let args = arg_vars
                 .into_iter()
                 .map(|index| {
@@ -4217,9 +4217,23 @@ fn flat_type_to_err_type(
 
             let ret = var_to_err_type(subs, state, ret_var, Polarity::Pos);
             let closure = var_to_err_type(subs, state, closure_var, pol);
+            let fx = match subs.get_content_without_compacting(fx_var) {
+                Content::Pure | Content::FlexVar(_) | Content::Error => ErrorFunctionFx::Pure,
+                Content::Effectful => ErrorFunctionFx::Effectful,
+                Content::RigidVar(_)
+                | Content::FlexAbleVar(_, _)
+                | Content::RigidAbleVar(_, _)
+                | Content::RecursionVar { .. }
+                | Content::LambdaSet(_)
+                | Content::ErasedLambda
+                | Content::Structure(_)
+                | Content::Alias(_, _, _, _)
+                | Content::RangedNumber(_) => {
+                    internal_error!("Unexpected content in fx var")
+                }
+            };
 
-            // [purity-inference] TODO: add fx var to the error type
+            ErrorType::Function(args, Box::new(closure), fx, Box::new(ret))
-            ErrorType::Function(args, Box::new(closure), Box::new(ret))
         }
 
         EmptyRecord => ErrorType::Record(SendMap::default(), TypeExt::Closed),

crates/compiler/types/src/types.rs

@@ -3680,12 +3680,23 @@ pub enum ErrorType {
         TypeExt,
         Polarity,
     ),
-    Function(Vec<ErrorType>, Box<ErrorType>, Box<ErrorType>),
+    Function(
+        Vec<ErrorType>,
+        Box<ErrorType>,
+        ErrorFunctionFx,
+        Box<ErrorType>,
+    ),
     Alias(Symbol, Vec<ErrorType>, Box<ErrorType>, AliasKind),
     Range(Vec<ErrorType>),
     Error,
 }
 
+#[derive(PartialEq, Eq, Clone, Hash)]
+pub enum ErrorFunctionFx {
+    Pure,
+    Effectful,
+}
+
 impl std::fmt::Debug for ErrorType {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         // TODO remove clone
@@ -3731,7 +3742,7 @@ impl ErrorType {
                     .for_each(|(_, ts)| ts.iter().for_each(|t| t.add_names(taken)));
                 ext.add_names(taken);
             }
-            Function(args, capt, ret) => {
+            Function(args, capt, _fx, ret) => {
                 args.iter().for_each(|t| t.add_names(taken));
                 capt.add_names(taken);
                 ret.add_names(taken);
@@ -3817,7 +3828,7 @@ fn write_error_type_help(
                 }
             }
         }
-        Function(arguments, _closure, result) => {
+        Function(arguments, _closure, fx, result) => {
             let write_parens = parens != Parens::Unnecessary;
 
             if write_parens {
@@ -3833,7 +3844,10 @@ fn write_error_type_help(
                 }
             }
 
-            buf.push_str(" -> ");
+            match fx {
+                ErrorFunctionFx::Pure => buf.push_str(" -> "),
+                ErrorFunctionFx::Effectful => buf.push_str(" => "),
+            }
 
             write_error_type_help(interns, *result, buf, Parens::InFn);
 
@@ -3967,7 +3981,7 @@ fn write_debug_error_type_help(error_type: ErrorType, buf: &mut String, parens:
                 buf.push(')');
             }
         }
-        Function(arguments, _closure, result) => {
+        Function(arguments, _closure, fx, result) => {
             let write_parens = parens != Parens::Unnecessary;
 
             if write_parens {
@@ -3983,7 +3997,10 @@ fn write_debug_error_type_help(error_type: ErrorType, buf: &mut String, parens:
                 }
             }
 
-            buf.push_str(" -> ");
+            match fx {
+                ErrorFunctionFx::Pure => buf.push_str(" -> "),
+                ErrorFunctionFx::Effectful => buf.push_str(" => "),
+            }
 
             write_debug_error_type_help(*result, buf, Parens::InFn);
 

crates/glue/src/types.rs

@@ -1406,7 +1406,6 @@ fn add_type_help<'a>(
             }
         },
         Content::Structure(FlatType::Func(args, closure_var, ret_var, _fx_var)) => {
-            // [purity-inference] TODO: fx var
             let is_toplevel = false; // or in any case, we cannot assume that we are
 
             add_function_type(

crates/reporting/src/error/type.rs

@@ -1846,7 +1846,7 @@ fn describe_wanted_function(tipe: &ErrorType) -> DescribedFunction {
     use ErrorType::*;
 
     match tipe {
-        Function(args, _, _) => DescribedFunction::Arguments(args.len()),
+        Function(args, _, _, _) => DescribedFunction::Arguments(args.len()),
         Alias(_, _, actual, AliasKind::Structural) => describe_wanted_function(actual),
         Alias(_, _, actual, AliasKind::Opaque) => {
             let tag = if matches!(
@@ -2698,12 +2698,13 @@ fn to_doc_help<'b>(
     use ErrorType::*;
 
     match tipe {
-        Function(args, _, ret) => report_text::function(
+        Function(args, _, fx, ret) => report_text::function(
             alloc,
             parens,
             args.into_iter()
                 .map(|arg| to_doc_help(ctx, gen_usages, alloc, Parens::InFn, arg))
                 .collect(),
+            fx,
             to_doc_help(ctx, gen_usages, alloc, Parens::InFn, *ret),
         ),
         Infinite => alloc.text("∞"),
@@ -2940,7 +2941,7 @@ fn count_generated_name_usages<'a>(
                 stack.extend(tags.values().flatten().map(|t| (t, only_unseen)));
                 ext_stack.push((ext, only_unseen));
             }
-            Function(args, _lset, ret) => {
+            Function(args, _lset, _fx, ret) => {
                 stack.extend(args.iter().map(|t| (t, only_unseen)));
                 stack.push((ret, only_unseen));
             }
@@ -3115,7 +3116,7 @@ fn to_diff<'b>(
             }
         }
 
-        (Function(args1, _, ret1), Function(args2, _, ret2)) => {
+        (Function(args1, _, fx1, ret1), Function(args2, _, fx2, ret2)) => {
             if args1.len() == args2.len() {
                 let mut status = Status::Similar;
                 let arg_diff = diff_args(alloc, Parens::InFn, args1, args2);
@@ -3123,8 +3124,8 @@ fn to_diff<'b>(
                 status.merge(arg_diff.status);
                 status.merge(ret_diff.status);
 
-                let left = report_text::function(alloc, parens, arg_diff.left, ret_diff.left);
+                let left = report_text::function(alloc, parens, arg_diff.left, fx1, ret_diff.left);
-                let right = report_text::function(alloc, parens, arg_diff.right, ret_diff.right);
+                let right = report_text::function(alloc, parens, arg_diff.right, fx2, ret_diff.right);
                 let mut left_able = arg_diff.left_able;
                 left_able.extend(ret_diff.left_able);
                 let mut right_able = arg_diff.right_able;
@@ -3713,9 +3714,10 @@ fn should_show_diff(t1: &ErrorType, t2: &ErrorType) -> bool {
                         .any(|(p1, p2)| should_show_diff(p1, p2))
                 })
         }
-        (Function(params1, ret1, l1), Function(params2, ret2, l2)) => {
+        (Function(params1, ret1, fx1, l1), Function(params2, ret2, fx2, l2)) => {
             if params1.len() != params2.len()
                 || should_show_diff(ret1, ret2)
+                || fx1 != fx2
                 || should_show_diff(l1, l2)
             {
                 return true;
@@ -3777,8 +3779,8 @@ fn should_show_diff(t1: &ErrorType, t2: &ErrorType) -> bool {
         | (_, TagUnion(_, _, _))
         | (RecursiveTagUnion(_, _, _, _), _)
         | (_, RecursiveTagUnion(_, _, _, _))
-        | (Function(_, _, _), _)
+        | (Function(_, _, _, _), _)
-        | (_, Function(_, _, _)) => true,
+        | (_, Function(_, _, _, _)) => true,
     }
 }
 
@@ -4236,7 +4238,7 @@ mod report_text {
     use crate::report::{Annotation, RocDocAllocator, RocDocBuilder};
     use roc_module::ident::Lowercase;
     use roc_types::pretty_print::Parens;
-    use roc_types::types::{ErrorType, RecordField, TypeExt};
+    use roc_types::types::{ErrorFunctionFx, ErrorType, RecordField, TypeExt};
     use ven_pretty::DocAllocator;
 
     fn with_parens<'b>(
@@ -4250,11 +4252,15 @@ mod report_text {
         alloc: &'b RocDocAllocator<'b>,
         parens: Parens,
         args: Vec<RocDocBuilder<'b>>,
+        fx: ErrorFunctionFx,
         ret: RocDocBuilder<'b>,
     ) -> RocDocBuilder<'b> {
         let function_doc = alloc.concat([
             alloc.intersperse(args, alloc.reflow(", ")),
-            alloc.reflow(" -> "),
+            match fx {
+                ErrorFunctionFx::Pure => alloc.text(" -> "),
+                ErrorFunctionFx::Effectful => alloc.text(" => "),
+            },
             ret,
         ]);
 
@@ -4820,7 +4826,7 @@ fn type_problem_to_pretty<'b>(
                     rigid_able_vs_different_flex_able(x, abilities, other_abilities)
                 }
                 RigidVar(y) | RigidAbleVar(y, _) => bad_double_rigid(x, y),
-                Function(_, _, _) => rigid_able_vs_concrete(x, alloc.reflow("a function value")),
+                Function(_, _, _, _) => rigid_able_vs_concrete(x, alloc.reflow("a function value")),
                 Record(_, _) => rigid_able_vs_concrete(x, alloc.reflow("a record value")),
                 Tuple(_, _) => rigid_able_vs_concrete(x, alloc.reflow("a tuple value")),
                 TagUnion(_, _, _) | RecursiveTagUnion(_, _, _, _) => {
@@ -4909,7 +4915,7 @@ fn type_problem_to_pretty<'b>(
                     bad_rigid_var(x, msg)
                 }
                 RigidVar(y) | RigidAbleVar(y, _) => bad_double_rigid(x, y),
-                Function(_, _, _) => bad_rigid_var(x, alloc.reflow("a function value")),
+                Function(_, _, _, _) => bad_rigid_var(x, alloc.reflow("a function value")),
                 Record(_, _) => bad_rigid_var(x, alloc.reflow("a record value")),
                 Tuple(_, _) => bad_rigid_var(x, alloc.reflow("a tuple value")),
                 TagUnion(_, _, _) | RecursiveTagUnion(_, _, _, _) => {