add ListIsUnique lowlevel operation

compiler/builtins/bitcode/src/list.zig

@@ -1355,3 +1355,9 @@ pub fn listFindUnsafe(
         return .{ .value = null, .found = false };
     }
 }
+
+pub fn listIsUnique(
+    list: RocList,
+) callconv(.C) bool {
+    return list.isEmpty() or list.isUnique();
+}

compiler/builtins/bitcode/src/main.zig

@@ -56,6 +56,7 @@ comptime {
     exportListFn(list.listAny, "any");
     exportListFn(list.listAll, "all");
     exportListFn(list.listFindUnsafe, "find_unsafe");
+    exportListFn(list.listIsUnique, "is_unique");
 }
 
 // Dict Module

compiler/builtins/src/bitcode.rs

@@ -345,6 +345,7 @@ pub const LIST_REPLACE_IN_PLACE: &str = "roc_builtins.list.replace_in_place";
 pub const LIST_ANY: &str = "roc_builtins.list.any";
 pub const LIST_ALL: &str = "roc_builtins.list.all";
 pub const LIST_FIND_UNSAFE: &str = "roc_builtins.list.find_unsafe";
+pub const LIST_IS_UNIQUE: &str = "roc_builtins.list.is_unique";
 
 pub const DEC_FROM_STR: &str = "roc_builtins.dec.from_str";
 pub const DEC_FROM_F64: &str = "roc_builtins.dec.from_f64";

compiler/can/src/builtins.rs

@@ -150,6 +150,7 @@ pub fn builtin_defs_map(symbol: Symbol, var_store: &mut VarStore) -> Option<Def>
         LIST_ANY => list_any,
         LIST_ALL => list_all,
         LIST_FIND => list_find,
+        LIST_IS_UNIQUE => list_is_unique,
         DICT_LEN => dict_len,
         DICT_EMPTY => dict_empty,
         DICT_SINGLE => dict_single,
@@ -3773,6 +3774,11 @@ fn list_find(symbol: Symbol, var_store: &mut VarStore) -> Def {
     )
 }
 
+/// List.isUnique : List * -> Bool
+fn list_is_unique(symbol: Symbol, var_store: &mut VarStore) -> Def {
+    lowlevel_1(symbol, LowLevel::ListIsUnique, var_store)
+}
+
 /// Dict.len : Dict * * -> Nat
 fn dict_len(symbol: Symbol, var_store: &mut VarStore) -> Def {
     let arg1_var = var_store.fresh();

compiler/gen_llvm/src/llvm/build.rs

@@ -5667,6 +5667,15 @@ fn run_low_level<'a, 'ctx, 'env>(
                 update_mode,
             )
         }
+        ListIsUnique => {
+            // List.isUnique : List a -> Bool
+            debug_assert_eq!(args.len(), 1);
+
+            let list = load_symbol(scope, &args[0]);
+            let list = list_to_c_abi(env, list).into();
+
+            call_bitcode_fn(env, &[list], bitcode::LIST_IS_UNIQUE)
+        }
         NumToStr => {
             // Num.toStr : Num a -> Str
             debug_assert_eq!(args.len(), 1);

compiler/gen_wasm/src/low_level.rs

@@ -277,6 +277,8 @@ impl<'a> LowLevelCall<'a> {
                 _ => internal_error!("invalid storage for List"),
             },
 
+            ListIsUnique => self.load_args_and_call_zig(backend, bitcode::LIST_IS_UNIQUE),
+
             ListMap | ListMap2 | ListMap3 | ListMap4 | ListMapWithIndex | ListKeepIf | ListWalk
             | ListWalkUntil | ListWalkBackwards | ListKeepOks | ListKeepErrs | ListSortWith
             | ListAny | ListAll | ListFindUnsafe | DictWalk => {

compiler/module/src/low_level.rs

@@ -53,6 +53,7 @@ pub enum LowLevel {
     ListAny,
     ListAll,
     ListFindUnsafe,
+    ListIsUnique,
     DictSize,
     DictEmpty,
     DictInsert,

compiler/module/src/symbol.rs

@@ -1252,6 +1252,7 @@ define_builtins! {
         55 LIST_SORT_DESC: "sortDesc"
         56 LIST_SORT_DESC_COMPARE: "#sortDescCompare"
         57 LIST_REPLACE: "replace"
+        58 LIST_IS_UNIQUE: "#isUnique"
     }
     5 RESULT: "Result" => {
         0 RESULT_RESULT: "Result" // the Result.Result type alias

compiler/mono/src/borrow.rs

@@ -1031,6 +1031,8 @@ pub fn lowlevel_borrow_signature(arena: &Bump, op: LowLevel) -> &[bool] {
 
         ExpectTrue => arena.alloc_slice_copy(&[irrelevant]),
 
+        ListIsUnique => arena.alloc_slice_copy(&[borrowed]),
+
         BoxExpr | UnboxExpr => {
             unreachable!("These lowlevel operations are turned into mono Expr's")
         }