Merge pull request #41144 from vsapsai/accept-demoted-tagdecl

Make isVisibleFromModule accept TagDecl definitions that were demoted to declarations.

Author: vsapsai

lib/ClangImporter/ClangImporter.cpp

@@ -2705,9 +2705,12 @@ static bool isVisibleFromModule(const ClangModuleUnit *ModuleFilter,
 
     // For enums, structs, and unions, only count definitions when looking to
     // see what other modules they appear in.
-    if (IsTagDecl)
-      if (!cast<clang::TagDecl>(Redeclaration)->isCompleteDefinition())
+    if (IsTagDecl) {
+      auto TD = cast<clang::TagDecl>(Redeclaration);
+      if (!TD->isCompleteDefinition() &&
+          !TD->isThisDeclarationADemotedDefinition())
         continue;
+    }
 
     auto OwningClangModule = getClangTopLevelOwningModule(Redeclaration,
                                                           ClangASTContext);

test/ClangImporter/overlay.swift

@@ -17,6 +17,5 @@ let encoding: UInt = NSUTF8StringEncoding
 let viaTypedef: Redeclaration.NSPoint = AppKit.NSPoint(x: 0, y: 0)
 Redeclaration.NSStringToNSString(AppKit.NSStringToNSString("abc")) // expected-warning {{result of call to 'NSStringToNSString' is unused}}
 
-/// The following error should soon be introduced by https://github.com/apple/llvm-project/pull/3497.
-let viaStruct: Redeclaration.FooStruct1 = AppKit.FooStruct1() // expected-error * {{module 'AppKit' has no member named 'FooStruct1'}}
+let viaStruct: Redeclaration.FooStruct1 = AppKit.FooStruct1()
 let forwardDecl: Redeclaration.Tribool = AppKit.Tribool() // expected-error {{no type named 'Tribool' in module 'Redeclaration'}}