[Sema] Avoid computing raw values for enum cases in swiftinterface files

Raw values of enum cases from another module are not specified in the declaration of the enum unless that enum is `@objc`. This meant that `EnumRawValuesRequest` was computing potentially incorrect raw values when the enum declaration supported it and was emitting incorrect diagnostics for other enum decls.

Resolves SR-14355 and rdar://75451691

Author: tshortli

lib/Sema/TypeCheckDecl.cpp

@@ -1094,6 +1094,14 @@ EnumRawValuesRequest::evaluate(Evaluator &eval, EnumDecl *ED,
   if (!rawTy) {
     return std::make_tuple<>();
   }
+  
+  // Avoid computing raw values for enum cases in swiftinterface files since raw
+  // values are intentionally omitted from them (unless the enum is @objc).
+  // Without bailing here, incorrect raw values can be automatically generated
+  // and incorrect diagnostics may be omitted for some decls.
+  SourceFile *Parent = ED->getDeclContext()->getParentSourceFile();
+  if (Parent && Parent->Kind == SourceFileKind::Interface && !ED->isObjC())
+    return std::make_tuple<>();
 
   if (!computeAutomaticEnumValueKind(ED)) {
     return std::make_tuple<>();

test/ModuleInterface/Inputs/enums-layout-helper.swift

@@ -46,6 +46,12 @@ public enum FutureproofEnum: Int {
   case d
 }
 
+// CHECK-LABEL: public enum FutureproofUnicodeScalarEnum : Swift.Unicode.Scalar
+public enum FutureproofUnicodeScalarEnum: Unicode.Scalar {
+  // CHECK-NEXT: case a{{$}}
+  case a = "A"
+}
+
 // CHECK-LABEL: indirect public enum FutureproofIndirectEnum
 public indirect enum FutureproofIndirectEnum {
   // CHECK-NEXT: case a{{$}}

test/ModuleInterface/enums-layout.swift

@@ -42,6 +42,16 @@ func testFrozenObjCEnum() -> FrozenObjCEnum {
   return .b
 } // CHECK-NEXT: {{^}$}}
 
+// CHECK-LABEL: define{{.+}}testFutureproofUnicodeScalarEnum
+func testFutureproofUnicodeScalarEnum() -> FutureproofUnicodeScalarEnum {
+  // CHECK: [[CASE:%.+]] = load i32, i32* @"$s3Lib28FutureproofUnicodeScalarEnumO1ayA2CmFWC"
+  // CHECK: [[METADATA_RESPONSE:%.+]] = tail call swiftcc %swift.metadata_response @"$s3Lib28FutureproofUnicodeScalarEnumOMa"
+  // CHECK: [[METADATA:%.+]] = extractvalue %swift.metadata_response [[METADATA_RESPONSE]], 0
+  // CHECK: call void {{%.+}}(%swift.opaque* noalias %0, i32 [[CASE]], %swift.type* [[METADATA]])
+  // CHECK-NEXT: ret void
+  return .a
+}
+
 // CHECK-LABEL: define{{.+}}testFutureproofIndirectEnum
 func testFutureproofIndirectEnum() -> FutureproofIndirectEnum {
   // CHECK: [[CASE:%.+]] = load i32, i32* @"$s3Lib23FutureproofIndirectEnumO1cyA2CmFWC"