Merge pull request #4082 from roc-lang/update-cli-platform-unreachables

Support unification with uninhabited tag variants in more places

crates/compiler/solve/src/solve.rs

@@ -1356,16 +1356,8 @@ fn solve(
                 );
 
                 let snapshot = subs.snapshot();
-                let unify_cond_and_patterns_outcome = {
-                    // When unifying the cond type with what the branches expect, allow the
-                    // branches to gain constructors that are uninabited; that way, we can permit
-                    // unification of things like
-                    //   [Ok Str] ~ [Ok Str, Result []]
-                    // which we want here, because `Result []` need not be matched - it is
-                    // impossible to construct!
-                    let mode = Mode::EQ_WITH_EXTENSION_BY_UNINHABITED_TYPES;
-                    unify(&mut UEnv::new(subs), branches_var, real_var, mode)
-                };
+                let unify_cond_and_patterns_outcome =
+                    unify(&mut UEnv::new(subs), branches_var, real_var, Mode::EQ);
 
                 let should_check_exhaustiveness;
                 match unify_cond_and_patterns_outcome {

crates/compiler/solve/tests/solve_expr.rs

@@ -7791,4 +7791,36 @@ mod solve_expr {
             "Str",
         );
     }
+
+    #[test]
+    fn match_on_result_with_uninhabited_error_destructuring() {
+        infer_eq_without_problem(
+            indoc!(
+                r#"
+                x : Result Str []
+                x = Ok "abc"
+
+                Ok str = x
+
+                str
+                "#
+            ),
+            "Str",
+        );
+    }
+
+    #[test]
+    fn match_on_result_with_uninhabited_error_destructuring_in_lambda_syntax() {
+        infer_eq_without_problem(
+            indoc!(
+                r#"
+                x : Result Str [] -> Str
+                x = \Ok s -> s
+
+                x
+                "#
+            ),
+            "Result Str [] -> Str",
+        );
+    }
 }