[ClangImporter] Give compatibility typealiases the correct version.

Unlike values, we can't import multiple copies of types under
different names and get good results. Instead, we make a typealias
that points back to the original type. Make sure this typealias is
flagged with whatever version is appropriate, rather than always using
"Swift 2".

Author: jrose-apple

lib/ClangImporter/ImportDecl.cpp

@@ -2041,10 +2041,11 @@ namespace {
       decl->setImplicit();
     }
 
-    /// Create a typealias for the Swift 2 name of a Clang type declaration.
-    Decl *importSwift2TypeAlias(const clang::NamedDecl *decl,
-                                ImportedName swift2Name,
-                                ImportedName correctSwiftName);
+    /// Create a typealias for the name of a Clang type declaration in an
+    /// alternate version of Swift.
+    Decl *importCompatibilityTypeAlias(const clang::NamedDecl *decl,
+                                       ImportedName compatibilityName,
+                                       ImportedName correctSwiftName);
 
     /// Create a swift_newtype struct corresponding to a typedef. Returns
     /// nullptr if unable.
@@ -2062,7 +2063,8 @@ namespace {
       // If we've been asked to produce a Swift 2 stub, handle it via a
       // typealias.
       if (correctSwiftName)
-        return importSwift2TypeAlias(Decl, importedName, *correctSwiftName);
+        return importCompatibilityTypeAlias(Decl, importedName,
+                                            *correctSwiftName);
 
       Type SwiftType;
       if (Decl->getDeclContext()->getRedeclContext()->isTranslationUnit()) {
@@ -2277,7 +2279,8 @@ namespace {
       // If we've been asked to produce a Swift 2 stub, handle it via a
       // typealias.
       if (correctSwiftName)
-        return importSwift2TypeAlias(decl, importedName, *correctSwiftName);
+        return importCompatibilityTypeAlias(decl, importedName,
+                                            *correctSwiftName);
 
       auto dc =
           Impl.importDeclContextOf(decl, importedName.getEffectiveContext());
@@ -2693,7 +2696,8 @@ namespace {
       // If we've been asked to produce a Swift 2 stub, handle it via a
       // typealias.
       if (correctSwiftName)
-        return importSwift2TypeAlias(decl, importedName, *correctSwiftName);
+        return importCompatibilityTypeAlias(decl, importedName,
+                                            *correctSwiftName);
 
       auto dc =
           Impl.importDeclContextOf(decl, importedName.getEffectiveContext());
@@ -3957,7 +3961,8 @@ namespace {
       // If we've been asked to produce a Swift 2 stub, handle it via a
       // typealias.
       if (correctSwiftName)
-        return importSwift2TypeAlias(decl, importedName, *correctSwiftName);
+        return importCompatibilityTypeAlias(decl, importedName,
+                                            *correctSwiftName);
 
       Identifier name = importedName.getDeclName().getBaseName();
 
@@ -4092,7 +4097,8 @@ namespace {
       // If we've been asked to produce a Swift 2 stub, handle it via a
       // typealias.
       if (correctSwiftName)
-        return importSwift2TypeAlias(decl, importedName, *correctSwiftName);
+        return importCompatibilityTypeAlias(decl, importedName,
+                                            *correctSwiftName);
 
       auto name = importedName.getDeclName().getBaseName();
 
@@ -4630,9 +4636,10 @@ SwiftDeclConverter::importCFClassType(const clang::TypedefNameDecl *decl,
   return theClass;
 }
 
-Decl *SwiftDeclConverter::importSwift2TypeAlias(const clang::NamedDecl *decl,
-                                                ImportedName swift2Name,
-                                                ImportedName correctSwiftName) {
+Decl *SwiftDeclConverter::importCompatibilityTypeAlias(
+    const clang::NamedDecl *decl,
+    ImportedName compatibilityName,
+    ImportedName correctSwiftName) {
   // Import the referenced declaration. If it doesn't come in as a type,
   // we don't care.
   auto importedDecl = Impl.importDecl(decl, getActiveSwiftVersion());
@@ -4665,19 +4672,14 @@ Decl *SwiftDeclConverter::importSwift2TypeAlias(const clang::NamedDecl *decl,
 
   // Create the type alias.
   auto alias = Impl.createDeclWithClangNode<TypeAliasDecl>(
-      decl,
-      Accessibility::Public, Impl.importSourceLoc(decl->getLocStart()),
-      SourceLoc(), swift2Name.getDeclName().getBaseName(),
-      Impl.importSourceLoc(decl->getLocation()),
-      genericParams, dc);
+      decl, Accessibility::Public, Impl.importSourceLoc(decl->getLocStart()),
+      SourceLoc(), compatibilityName.getDeclName().getBaseName(),
+      Impl.importSourceLoc(decl->getLocation()), genericParams, dc);
   alias->setUnderlyingType(underlyingType);
   alias->setGenericEnvironment(genericEnv);
 
-  // Record that this is the Swift 2 version of this declaration.
-  Impl.ImportedDecls[{decl->getCanonicalDecl(), ImportNameVersion::Swift2}] =
-      alias;
-
-  // Mark it as the Swift 2 variant.
+  // Record that this is the official version of this declaration.
+  Impl.ImportedDecls[{decl->getCanonicalDecl(), getVersion()}] = alias;
   markAsVariant(alias, correctSwiftName);
   return alias;
 }

test/APINotes/Inputs/custom-frameworks/APINotesFrameworkTest.framework/Headers/APINotesFrameworkTest.apinotes

@@ -89,3 +89,6 @@ SwiftVersions:
       - Name: acceptDoublePointer
         SwiftName: 'acceptPointer(_:)'
         Nullability: [ O ]
+    Tags:
+      - Name: SomeCStruct
+        SwiftName: ImportantCStruct

test/APINotes/Inputs/custom-frameworks/APINotesFrameworkTest.framework/Headers/APINotesFrameworkTest.h

@@ -19,3 +19,4 @@ __attribute__((objc_root_class))
 
 #import <APINotesFrameworkTest/Properties.h>
 #import <APINotesFrameworkTest/Protocols.h>
+#import <APINotesFrameworkTest/Types.h>

test/APINotes/Inputs/custom-frameworks/APINotesFrameworkTest.framework/Headers/Types.h

@@ -0,0 +1,7 @@
+#pragma clang assume_nonnull begin
+
+struct __attribute__((swift_name("VeryImportantCStruct"))) SomeCStruct {
+	int field;
+};
+
+#pragma clang assume_nonnull end

test/APINotes/versioned.swift

@@ -23,20 +23,36 @@ func testRenamedTopLevel() {
   // CHECK-DIAGS-3: versioned.swift:[[@LINE-1]]:3: error: 'accept' has been renamed to 'acceptPointer(_:)'
   // CHECK-DIAGS-3: note: 'accept' was introduced in Swift 4
 
-  // CHECK-DIAGS-4-NOT: versioned.swift:[[@LINE+1]]:
+  // CHECK-DIAGS-3-NOT: versioned.swift:[[@LINE+1]]:
   acceptPointer(&value)
   // CHECK-DIAGS-4: versioned.swift:[[@LINE-1]]:3: error: 'acceptPointer' has been renamed to 'accept(_:)'
   // CHECK-DIAGS-4: note: 'acceptPointer' was obsoleted in Swift 4
 
   acceptDoublePointer(&value)
   // CHECK-DIAGS: versioned.swift:[[@LINE-1]]:3: error: 'acceptDoublePointer' has been renamed to
-  // CHECK-DIAGS-4: 'accept(_:)'
-  // CHECK-DIAGS-3: 'acceptPointer(_:)'
+  // CHECK-DIAGS-4-SAME: 'accept(_:)'
+  // CHECK-DIAGS-3-SAME: 'acceptPointer(_:)'
   // CHECK-DIAGS: note: 'acceptDoublePointer' was obsoleted in Swift 3
 
   oldAcceptDoublePointer(&value)
   // CHECK-DIAGS: versioned.swift:[[@LINE-1]]:3: error: 'oldAcceptDoublePointer' has been renamed to
-  // CHECK-DIAGS-4: 'accept(_:)'
-  // CHECK-DIAGS-3: 'acceptPointer(_:)'
+  // CHECK-DIAGS-4-SAME: 'accept(_:)'
+  // CHECK-DIAGS-3-SAME: 'acceptPointer(_:)'
   // CHECK-DIAGS: note: 'oldAcceptDoublePointer' has been explicitly marked unavailable here
+
+  _ = SomeCStruct()
+  // CHECK-DIAGS: versioned.swift:[[@LINE-1]]:7: error: 'SomeCStruct' has been renamed to
+  // CHECK-DIAGS-4-SAME: 'VeryImportantCStruct'
+  // CHECK-DIAGS-3-SAME: 'ImportantCStruct'
+  // CHECK-DIAGS: note: 'SomeCStruct' was obsoleted in Swift 3
+
+  // CHECK-DIAGS-3-NOT: versioned.swift:[[@LINE+1]]:
+  _ = ImportantCStruct()
+  // CHECK-DIAGS-4: versioned.swift:[[@LINE-1]]:7: error: 'ImportantCStruct' has been renamed to 'VeryImportantCStruct'
+  // CHECK-DIAGS-4: note: 'ImportantCStruct' was obsoleted in Swift 4
+
+  // CHECK-DIAGS-4-NOT: versioned.swift:[[@LINE+1]]:
+  _ = VeryImportantCStruct()
+  // CHECK-DIAGS-3: versioned.swift:[[@LINE-1]]:7: error: 'VeryImportantCStruct' has been renamed to 'ImportantCStruct'
+  // CHECK-DIAGS-3: note: 'VeryImportantCStruct' was introduced in Swift 4
 }