[PrintAsObjC] Handle the importer's compatibility typealiases. (#10042)

These are TypeAliasDecls whose Clang nodes are not TypedefNameDecls.
This worked all right for classes, but dropped the tag keyword
(e.g. 'struct') for tag decls with names of their own, and didn't
print any name at all for C types that used the
typedef-for-anonymous-tag pattern.

rdar://problem/32514335

Author: jrose-apple

lib/AST/SwiftNameTranslation.cpp

@@ -28,7 +28,8 @@ using namespace swift;
 StringRef swift::objc_translation::
 getNameForObjC(const ValueDecl *VD, CustomNamesOnly_t customNamesOnly) {
   assert(isa<ClassDecl>(VD) || isa<ProtocolDecl>(VD) || isa<StructDecl>(VD) ||
-         isa<EnumDecl>(VD) || isa<EnumElementDecl>(VD));
+         isa<EnumDecl>(VD) || isa<EnumElementDecl>(VD) ||
+         isa<TypeAliasDecl>(VD));
   if (auto objc = VD->getAttrs().getAttribute<ObjCAttr>()) {
     if (auto name = objc->getName()) {
       assert(name->getNumSelectorPieces() == 1);

lib/PrintAsObjC/PrintAsObjC.cpp

@@ -1366,7 +1366,8 @@ class ObjCPrinter : private DeclVisitor<ObjCPrinter>,
     if (alias->hasClangNode()) {
       if (auto *clangTypeDecl =
             dyn_cast<clang::TypeDecl>(alias->getClangDecl())) {
-        os << clangTypeDecl->getName();
+        maybePrintTagKeyword(alias);
+        os << getNameForObjC(alias);
 
         if (isClangPointerType(clangTypeDecl))
           printNullability(optionalKind);
@@ -1392,7 +1393,7 @@ class ObjCPrinter : private DeclVisitor<ObjCPrinter>,
     visitPart(alias->getUnderlyingTypeLoc().getType(), optionalKind);
   }
 
-  void maybePrintTagKeyword(const NominalTypeDecl *NTD) {
+  void maybePrintTagKeyword(const TypeDecl *NTD) {
     if (isa<EnumDecl>(NTD) && !NTD->hasClangNode()) {
       os << "enum ";
       return;

test/PrintAsObjC/Inputs/custom-modules/NestedClass.apinotes

@@ -4,3 +4,11 @@ SwiftVersions:
     Classes:
       - Name: InnerClass
         SwiftName: InnerClass
+    Tags:
+      - Name: InnerStruct
+        SwiftName: InnerStruct
+    Typedefs:
+      - Name: InnerAlias
+        SwiftName: InnerAlias
+      - Name: InnerAnonStruct
+        SwiftName: InnerAnonStruct

test/PrintAsObjC/Inputs/custom-modules/NestedClass.h

@@ -8,3 +8,14 @@
 __attribute__((swift_name("Outer.Inner")))
 @interface InnerClass : NSObject
 @end
+
+struct __attribute__((swift_name("Outer.InnerV"))) InnerStruct {
+  int value;
+};
+
+typedef struct {
+  int value;
+} InnerAnonStruct __attribute__((swift_name("Outer.InnerAS")));
+
+typedef int InnerAlias __attribute__((swift_name("Outer.InnerA")));
+

test/PrintAsObjC/versioned.swift

@@ -22,6 +22,12 @@ import NestedClass
 @objc class UsesNestedClass : NSObject {
   // CHECK-NEXT: - (InnerClass * _Nullable)foo SWIFT_WARN_UNUSED_RESULT;
   @objc func foo() -> InnerClass? { return nil }
+  // CHECK-NEXT: - (void)fooStruct:(struct InnerStruct)_;
+  @objc func fooStruct(_: InnerStruct) {}
+  // CHECK-NEXT: - (void)fooAnonStruct:(InnerAnonStruct)_;
+  @objc func fooAnonStruct(_: InnerAnonStruct) {}
+  // CHECK-NEXT: - (void)fooAlias:(InnerAlias)_;
+  @objc func fooAlias(_: InnerAlias) {}
 
   // CHECK-NEXT: - (nonnull instancetype)init OBJC_DESIGNATED_INITIALIZER;
 }