[NFC] Lift out common "canImportAsOptional" to a new header.

Author: varungandhi-apple

include/swift/AST/ClangSwiftTypeCorrespondence.h

@@ -0,0 +1,36 @@
+//=- ClangSwiftTypeCorrespondence.h - Relations between Clang & Swift types -=//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2019 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+//
+// This file describes some common relations between Clang types and Swift
+// types that are need by the ClangTypeConverter and parts of ClangImporter.
+//
+// Since ClangTypeConverter is an implementation detail, ClangImporter should
+// not depend on ClangTypeConverter.h.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SWIFT_AST_CLANG_SWIFT_TYPE_CORRESPONDENCE_H
+#define SWIFT_AST_CLANG_SWIFT_TYPE_CORRESPONDENCE_H
+
+namespace clang {
+class Type;
+}
+
+namespace swift {
+/// Checks whether a Clang type can be imported as a Swift Optional type.
+///
+/// For example, a `const uint8_t *` could be imported as
+/// `Optional<UnsafePointer<UInt8>>`.
+bool canImportAsOptional(const clang::Type *type);
+}
+
+#endif /* SWIFT_AST_CLANG_SWIFT_TYPE_CORRESPONDENCE_H */

lib/AST/CMakeLists.txt

@@ -34,6 +34,7 @@ add_swift_host_library(swiftAST STATIC
   AvailabilitySpec.cpp
   Builtins.cpp
   CaptureInfo.cpp
+  ClangSwiftTypeCorrespondence.cpp
   ClangTypeConverter.cpp
   ConcreteDeclRef.cpp
   ConformanceLookupTable.cpp

lib/AST/ClangSwiftTypeCorrespondence.cpp

@@ -0,0 +1,27 @@
+//- ClangSwiftTypeCorrespondence.cpp - Relations between Clang & Swift types -//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2019 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+//
+// See description in ClangSwiftTypeCorrespondence.h.
+//
+//===----------------------------------------------------------------------===//
+
+#include "swift/AST/ClangSwiftTypeCorrespondence.h"
+#include "clang/AST/Type.h"
+
+bool swift::canImportAsOptional(const clang::Type *type) {
+  // Note: this mimics ImportHint::canImportAsOptional.
+
+  // Includes CoreFoundation types such as CFStringRef (== struct CFString *).
+  return type && (type->isPointerType()
+                  || type->isBlockPointerType()
+                  || type->isObjCObjectPointerType());
+}

lib/AST/ClangTypeConverter.cpp

@@ -26,6 +26,7 @@
 
 #include "swift/AST/ASTContext.h"
 #include "swift/AST/ClangModuleLoader.h"
+#include "swift/AST/ClangSwiftTypeCorrespondence.h"
 #include "swift/AST/ExistentialLayout.h"
 #include "swift/AST/Module.h"
 #include "swift/AST/Type.h"
@@ -460,7 +461,10 @@ ClangTypeConverter::visitBoundGenericType(BoundGenericType *type) {
   if (type->getDecl()->isOptionalDecl()) {
     auto args = type->getGenericArgs();
     assert((args.size() == 1) && "Optional should have 1 generic argument.");
-    return convert(args[0]);
+    clang::QualType innerTy = convert(args[0]);
+    if (swift::canImportAsOptional(innerTy.getTypePtrOrNull()))
+      return innerTy;
+    return clang::QualType();
   }
 
   auto swiftStructDecl = type->getDecl();

lib/ClangImporter/ImportName.cpp

@@ -21,6 +21,7 @@
 #include "ClangDiagnosticConsumer.h"
 #include "swift/Subsystems.h"
 #include "swift/AST/ASTContext.h"
+#include "swift/AST/ClangSwiftTypeCorrespondence.h"
 #include "swift/AST/DiagnosticEngine.h"
 #include "swift/AST/DiagnosticsClangImporter.h"
 #include "swift/AST/Module.h"
@@ -170,19 +171,6 @@ static bool isIntegerType(clang::QualType clangType) {
   return false;
 }
 
-/// Whether the given Objective-C type can be imported as an optional type.
-static bool canImportAsOptional(clang::ASTContext &ctx, clang::QualType type) {
-  // Note: this mimics ImportHint::canImportAsOptional.
-
-  // Objective-C object pointers.
-  if (type->getAs<clang::ObjCObjectPointerType>()) return true;
-
-  // Block and C pointers, including CF types.
-  if (type->isBlockPointerType() || type->isPointerType()) return true;
-
-  return false;
-}
-
 static Optional<ForeignErrorConvention::Kind>
 classifyMethodErrorHandling(const clang::ObjCMethodDecl *clangDecl,
                             OptionalTypeKind resultOptionality) {
@@ -202,7 +190,8 @@ classifyMethodErrorHandling(const clang::ObjCMethodDecl *clangDecl,
     // non-optional type.
     case clang::SwiftErrorAttr::NullResult:
       if (resultOptionality != OTK_None &&
-          canImportAsOptional(clangCtx, clangDecl->getReturnType()))
+          swift::canImportAsOptional(
+            clangDecl->getReturnType().getTypePtrOrNull()))
         return ForeignErrorConvention::NilResult;
       return None;
 
@@ -235,7 +224,8 @@ classifyMethodErrorHandling(const clang::ObjCMethodDecl *clangDecl,
 
   // For optional reference results, a nil value is normally an error.
   if (resultOptionality != OTK_None &&
-      canImportAsOptional(clangCtx, clangDecl->getReturnType())) {
+      swift::canImportAsOptional(
+        clangDecl->getReturnType().getTypePtrOrNull())) {
     return ForeignErrorConvention::NilResult;
   }
 

lib/PrintAsObjC/DeclAndTypePrinter.cpp

@@ -14,6 +14,7 @@
 
 #include "swift/AST/ASTContext.h"
 #include "swift/AST/ASTVisitor.h"
+#include "swift/AST/ClangSwiftTypeCorrespondence.h"
 #include "swift/AST/Comment.h"
 #include "swift/AST/Decl.h"
 #include "swift/AST/ExistentialLayout.h"
@@ -1559,8 +1560,7 @@ class DeclAndTypePrinter::Implementation
     ASTContext &ctx = getASTContext();
     auto &clangASTContext = ctx.getClangModuleLoader()->getClangASTContext();
     clang::QualType clangTy = clangASTContext.getTypeDeclType(clangTypeDecl);
-    return clangTy->isPointerType() || clangTy->isBlockPointerType() ||
-      clangTy->isObjCObjectPointerType();
+    return swift::canImportAsOptional(clangTy.getTypePtr());
   }
 
   bool printImportedAlias(const TypeAliasDecl *alias,