[ClangImporter] Handle -Xcc -include, sort of.

What does that mean? We'll indeed parse the provided prefix header.
If you aren't using a bridging header, that's all you get -- nothing
extra is made visible. If you /are/ using a bridging header, the prefix
header is prepended to it...but none of the modular content it imports
is made visible. I cloned rdar://problem/22083824 to fix that.

The important thing is that we /won't/ try to import overlays before
we've even finished setting up all the module loaders, and therefore
won't crash.

rdar://problem/20893290

Swift SVN r30831

Author: jrose-apple

lib/ClangImporter/ClangImporter.cpp

@@ -518,8 +518,6 @@ ClangImporter::create(ASTContext &ctx,
 
   clang::Preprocessor &clangPP = instance.getPreprocessor();
   clangPP.enableIncrementalProcessing();
-  auto *CB = new HeaderImportCallbacks(*importer, importer->Impl);
-  clangPP.addPPCallbacks(std::unique_ptr<clang::PPCallbacks>(CB));
 
   instance.createModuleManager();
   instance.getModuleManager()->addListener(
@@ -537,6 +535,9 @@ ClangImporter::create(ASTContext &ctx,
   clang::Parser::DeclGroupPtrTy parsed;
   while (!importer->Impl.Parser->ParseTopLevelDecl(parsed)) {}
 
+  auto *CB = new HeaderImportCallbacks(*importer, importer->Impl);
+  clangPP.addPPCallbacks(std::unique_ptr<clang::PPCallbacks>(CB));
+
   // Create the selectors we'll be looking for.
   auto &clangContext = importer->Impl.Instance->getASTContext();
   importer->Impl.objectAtIndexedSubscript

test/ClangModules/MixedSource/Inputs/Xcc_include.h

@@ -0,0 +1,3 @@
+@import Security;
+
+extern const int includedConst;

test/ClangModules/MixedSource/Xcc_include.swift

@@ -0,0 +1,26 @@
+// RUN: not %target-swift-frontend(mock-sdk: %clang-importer-sdk) -Xcc -include -Xcc %S/Inputs/Xcc_include.h -parse %s 2>&1 | FileCheck -check-prefix=CHECK-INCLUDE-ONLY %s
+
+// RUN: not %target-swift-frontend(mock-sdk: %clang-importer-sdk) -Xcc -include -Xcc %S/Inputs/Xcc_include.h -import-objc-header %S/../../Inputs/empty.swift -parse %s 2>&1 | FileCheck -check-prefix=CHECK-INCLUDE-PLUS-BRIDGING %s
+
+// RUN: not %target-swift-frontend(mock-sdk: %clang-importer-sdk) -Xcc -include -Xcc %S/Inputs/Xcc_include.h -F %S/Inputs/mixed-target/ -module-name Mixed -import-underlying-module -parse %s -disable-objc-attr-requires-foundation-module 2>&1 | FileCheck -check-prefix=CHECK-INCLUDE-FRAMEWORK %s
+
+// RUN: not %target-swift-frontend(mock-sdk: %clang-importer-sdk) -Xcc -include -Xcc %S/Inputs/this_header_does_not_exist.h -parse %s 2>&1 | FileCheck -check-prefix=CHECK-INCLUDE-MISSING %s
+
+// CHECK-INCLUDE-MISSING: error: '{{.*}}this_header_does_not_exist.h' file not found
+
+func test() {
+  // CHECK-INCLUDE-ONLY: error: use of unresolved identifier 'includedConst'
+  // CHECK-INCLUDE-PLUS-BRIDGING-NOT: unresolved identifier 'includedConst'
+  // CHECK-INCLUDE-FRAMEWORK: error: use of unresolved identifier 'includedConst'
+  _ = includedConst
+  
+  // CHECK-INCLUDE-ONLY: error: use of unresolved identifier 'errSecSuccess'
+  // CHECK-INCLUDE-PLUS-BRIDGING: error: use of unresolved identifier 'errSecSuccess'
+  // CHECK-INCLUDE-FRAMEWORK: error: use of unresolved identifier 'errSecSuccess'
+  _ = errSecSuccess
+
+#if FRAMEWORK
+  // CHECK-INCLUDE-FRAMEWORK-NOT: error: unresolved identifier 'Base'
+  _ = Base()
+#endif
+}

test/ClangModules/sdk-bridging-header.swift

@@ -1,8 +1,17 @@
 // RUN: %target-swift-frontend -parse -verify %s -import-objc-header %S/Inputs/sdk-bridging-header.h
 // RUN: not %target-swift-frontend -parse %s -import-objc-header %S/Inputs/bad-bridging-header.h 2>&1 | FileCheck -check-prefix=CHECK-FATAL %s
 
+// RUN: %target-swift-frontend -parse -verify %s -Xcc -include -Xcc %S/Inputs/sdk-bridging-header.h -import-objc-header %S/../Inputs/empty.swift
+
+// RUN: not %target-swift-frontend -parse %s -Xcc -include -Xcc %S/Inputs/bad-bridging-header.h 2>&1 | FileCheck -check-prefix=CHECK-INCLUDE %s
+// RUN: not %target-swift-frontend -parse %s -Xcc -include -Xcc %S/Inputs/bad-bridging-header.h -import-objc-header %S/../Inputs/empty.swift 2>&1 | FileCheck -check-prefix=CHECK-INCLUDE %s
+// RUN: not %target-swift-frontend -parse %s -Xcc -include -Xcc %S/Inputs/bad-bridging-header.h -import-objc-header %S/Inputs/sdk-bridging-header.h 2>&1 | FileCheck -check-prefix=CHECK-INCLUDE %s
+
 // CHECK-FATAL: failed to import bridging header
 
+// CHECK-INCLUDE: error: 'this-header-does-not-exist.h' file not found
+// CHECK-INCLUDE: error: use of unresolved identifier 'Predicate'
+
 // REQUIRES: objc_interop
 
 import Foundation