[Clang importer] Fix lookup of custom ref-counting ops in bridging headers

Lookup for custom reference counting operators into a precompiled bridging
header was causing a crash because there is no "underlying module" in which
to perform the lookup. Handle the lookup at the level of the main Swift
module for such cases, filtering out declarations not coming from Clang.

Fixes rdar://114495840.

Author: DougGregor

lib/ClangImporter/ClangImporter.cpp

@@ -30,6 +30,7 @@
 #include "swift/AST/ImportCache.h"
 #include "swift/AST/LinkLibrary.h"
 #include "swift/AST/Module.h"
+#include "swift/AST/ModuleNameLookup.h"
 #include "swift/AST/NameLookup.h"
 #include "swift/AST/NameLookupRequests.h"
 #include "swift/AST/PrettyStackTrace.h"
@@ -6917,9 +6918,23 @@ CustomRefCountingOperationResult CustomRefCountingOperation::evaluate(
   auto *clangMod = swiftDecl->getClangDecl()->getOwningModule();
   if (clangMod && clangMod->isSubModule())
     clangMod = clangMod->getTopLevelModule();
-  auto parentModule = ctx.getClangModuleLoader()->getWrapperForModule(clangMod);
-  ctx.lookupInModule(parentModule, name, results);
-
+  if (clangMod) {
+    auto parentModule = ctx.getClangModuleLoader()->getWrapperForModule(clangMod);
+    ctx.lookupInModule(parentModule, name, results);
+  } else {
+    // There is no Clang module for this declaration, so perform lookup from
+    // the main module. This will find declarations from the bridging header.
+    namelookup::lookupInModule(
+        ctx.MainModule, ctx.getIdentifier(name), results,
+        NLKind::UnqualifiedLookup, namelookup::ResolutionKind::Overloadable,
+        ctx.MainModule, SourceLoc(), NL_UnqualifiedDefault);
+
+    // Filter out any declarations that didn't come from Clang.
+    auto newEnd = std::remove_if(results.begin(), results.end(), [&](ValueDecl *decl) {
+      return !decl->getClangDecl();
+    });
+    results.erase(newEnd, results.end());
+  }
   if (results.size() == 1)
     return {CustomRefCountingOperationResult::foundOperation, results.front(),
             name};

test/Interop/Cxx/ergonomics/swift-bridging-annotations.swift

@@ -1,17 +1,32 @@
 // RUN: rm -rf %t
 // RUN: split-file %s %t
+// RUN: mkdir -p %t/pch
 
 // RUN: %target-swift-frontend %t/SwiftMod.swift -module-name SwiftMod -emit-module -o %t/SwiftMod.swiftmodule -I %t -enable-experimental-cxx-interop -Xcc -DFIRSTPASS
 
 // RUN: %target-swift-ide-test -print-module -module-to-print=SwiftMod -module-to-print=CxxModule -I %t -I %t/Inputs -I %swift_src_root/lib/ClangImporter -source-filename=x -enable-experimental-cxx-interop | %FileCheck %s
 
 // RUN: %target-swift-ide-test -print-module -module-to-print=SwiftMod -module-to-print=CxxModule -I %t -I %t/Inputs -I %swift_src_root/lib/ClangImporter -source-filename=x -enable-experimental-cxx-interop -Xcc -DINCMOD | %FileCheck %s
 
+// Test through the use of the bridging header
+// RUN: %target-swift-frontend -emit-ir -I %t -import-objc-header %t/Inputs/header.h -I %swift_src_root/lib/ClangImporter -enable-experimental-cxx-interop -DBRIDGING_HEADER_TEST -disable-availability-checking %t/SwiftMod.swift
+
+// Precompile the bridging header and test the use of that.
+// RUN: %target-swift-frontend -emit-pch -I %t -pch-output-dir %t/pch %t/Inputs/header.h -I %swift_src_root/lib/ClangImporter -enable-experimental-cxx-interop
+// RUN: %target-swift-frontend -emit-ir -I %t -pch-output-dir %t/pch -import-objc-header %t/Inputs/header.h -I %swift_src_root/lib/ClangImporter -enable-experimental-cxx-interop -DBRIDGING_HEADER_TEST -disable-availability-checking %t/SwiftMod.swift
+
+
 //--- SwiftMod.swift
 
 public protocol Proto {
 }
 
+#if BRIDGING_HEADER_TEST
+func f() -> SharedObject { return SharedObject.create() }
+
+func releaseSharedObject(_: SharedObject) { }
+#endif
+
 //--- Inputs/module.modulemap
 module CxxModule {
     header "header.h"