Downgrade To A Warning

Author: CodaFi

lib/Sema/TypeCheckPattern.cpp

@@ -1294,8 +1294,11 @@ Pattern *TypeChecker::coercePatternToType(ContextualPattern pattern,
       } else {
         // ...but for non-optional types it can never match! Diagnose it.
         diags.diagnose(NLE->getLoc(),
-                       diag::value_type_comparison_with_nil_illegal, type);
-        return nullptr;
+                       diag::value_type_comparison_with_nil_illegal, type)
+             .warnUntilSwiftVersion(6);
+
+        if (type->getASTContext().isSwiftVersionAtLeast(6))
+          return nullptr;
       }
     }
 

test/Constraints/result_builder_diags.swift

@@ -826,3 +826,30 @@ func test_redeclations() {
     let (foo, foo) = (5, 6) // expected-error {{invalid redeclaration of 'foo'}} expected-note {{'foo' previously declared here}}
   }
 }
+
+func test_rdar89742267() {
+  @resultBuilder
+  struct Builder {
+    static func buildBlock<T>(_ t: T) -> T { t }
+    static func buildEither<T>(first: T) -> T { first }
+    static func buildEither<T>(second: T) -> T { second }
+  }
+
+  struct S {}
+
+  enum Hey {
+    case listen
+  }
+
+  struct MyView {
+    var entry: Hey
+
+    @Builder var body: S {
+      switch entry {
+      case .listen: S()
+      case nil: S() // expected-warning {{type 'Hey' is not optional, value can never be nil; this is an error in Swift 6}}
+      default: S()
+      }
+    }
+  }
+}

test/stmt/switch_nil.swift

@@ -6,10 +6,9 @@ enum Hey {
 
 func test() {
   switch Hey.listen {
-  case nil: // expected-error{{type 'Hey' is not optional, value can never be nil}}
+  case nil: // expected-warning {{type 'Hey' is not optional, value can never be nil}}
     break
   default:
     break
   }
 }
-