[ClangImporter] Always rebuild any bridging PCH that has errors

If a PCH was output with errors, it may not have serialized all its
inputs. If there was a change to the search path or a headermap now
exists where it didn't previously, it's possible those inputs will now
be found. Ideally we would only rebuild in this particular case rather
than any error in general, but explicit module builds are the real
solution there. For now, just treat PCH with errors as out of date.

Resolves rdar://117037471.

Author: bnbarham

lib/ClangImporter/ClangImporter.cpp

@@ -894,9 +894,6 @@ bool ClangImporter::canReadPCH(StringRef PCHFilename) {
   invocation->getHeaderSearchOpts().ModulesValidateSystemHeaders = true;
   invocation->getLangOpts().NeededByPCHOrCompilationUsesPCH = true;
   invocation->getLangOpts().CacheGeneratedPCH = true;
-  // If the underlying invocation is allowing PCH errors, then it "can be read",
-  // even if it has its error bit set. Thus, don't override
-  // `AllowPCHWithCompilerErrors`.
 
   // ClangImporter::create adds a remapped MemoryBuffer that we don't need
   // here.  Moreover, it's a raw pointer owned by the preprocessor options; if
@@ -934,6 +931,14 @@ bool ClangImporter::canReadPCH(StringRef PCHFilename) {
     clang::ASTReader::ARR_OutOfDate |
     clang::ASTReader::ARR_VersionMismatch;
 
+  // If a PCH was output with errors, it may not have serialized all its
+  // inputs. If there was a change to the search path or a headermap now
+  // exists where it didn't previously, it's possible those inputs will now be
+  // found. Ideally we would only rebuild in this particular case rather than
+  // any error in general, but explicit module builds are the real solution
+  // there. For now, just treat PCH with errors as out of date.
+  failureCapabilities |= clang::ASTReader::ARR_TreatModuleWithErrorsAsOutOfDate;
+
   auto result = Reader.ReadAST(PCHFilename, clang::serialization::MK_PCH,
                                clang::SourceLocation(), failureCapabilities);
   switch (result) {

test/ClangImporter/AllowErrors/invalid-pch-bridging-header.swift

@@ -3,27 +3,48 @@
 // RUN: %empty-directory(%t)
 // RUN: mkdir -p %t/pch %t/pch-dir
 // RUN: split-file %s %t
+// RUN: sed -e "s|TEST_DIR|%/t|g" %t/hmap.json > %t/inner.json
 
 // Check that the pch is output even though it has errors
-// RUN: %target-swift-frontend -emit-pch -o %t/pch/bridging-header.pch -Xcc -Xclang -Xcc -fallow-pcm-with-compiler-errors -Xcc -Xclang -Xcc -fmodule-format=raw %t/bridging-header.h
-// RUN: %target-swift-frontend -typecheck -verify -import-objc-header %t/pch/bridging-header.pch -Xcc -Xclang -Xcc -fallow-pcm-with-compiler-errors -Xcc -Xclang -Xcc -fmodule-format=raw %t/use.swift
+// RUN: %target-swift-frontend -emit-pch -o %t/pch/bridging-header.pch -Xcc -Xclang -Xcc -fallow-pcm-with-compiler-errors -Xcc -Xclang -Xcc -fmodule-format=raw %t/bridging-header.h -Xcc -I%t/inner.hmap
+// RUN: not %target-swift-frontend -typecheck -import-objc-header %t/pch/bridging-header.pch -Xcc -Xclang -Xcc -fallow-pcm-with-compiler-errors -Xcc -Xclang -Xcc -fmodule-format=raw %t/use.swift -Xcc -I%t/inner.hmap 2>&1 | %FileCheck %s -check-prefix MISSING_HMAP
 // RUN: ls %t/pch/*.pch | count 1
 
 // Same but with implicit PCH instead
-// RUN: %target-swift-frontend -typecheck -verify -import-objc-header %t/bridging-header.h -pch-output-dir %t/pch-dir -Xcc -Xclang -Xcc -fallow-pcm-with-compiler-errors -Xcc -Xclang -Xcc -fmodule-format=raw %t/use.swift
+// RUN: not %target-swift-frontend -typecheck -import-objc-header %t/bridging-header.h -pch-output-dir %t/pch-dir -Xcc -Xclang -Xcc -fallow-pcm-with-compiler-errors -Xcc -Xclang -Xcc -fmodule-format=raw %t/use.swift -Xcc -I%t/inner.hmap 2>&1 | %FileCheck %s -check-prefix MISSING_HMAP
 // RUN: ls %t/pch-dir/*.pch | count 1
 
 // Second implicit run since we may go down a different path if the PCH already
 // exists
-// RUN: %target-swift-frontend -typecheck -verify -import-objc-header %t/bridging-header.h -pch-output-dir %t/pch-dir -Xcc -Xclang -Xcc -fallow-pcm-with-compiler-errors -Xcc -Xclang -Xcc -fmodule-format=raw %t/use.swift
+// RUN: not %target-swift-frontend -typecheck -import-objc-header %t/bridging-header.h -pch-output-dir %t/pch-dir -Xcc -Xclang -Xcc -fallow-pcm-with-compiler-errors -Xcc -Xclang -Xcc -fmodule-format=raw %t/use.swift -Xcc -I%t/inner.hmap 2>&1 | %FileCheck %s -check-prefix MISSING_HMAP
+// RUN: ls %t/pch-dir/*.pch | count 1
+
+// Create the headermap, should now have no errors
+// RUN: %hmaptool write %t/inner.json %t/inner.hmap
+// RUN: %target-swift-frontend -typecheck -verify -import-objc-header %t/bridging-header.h -pch-output-dir %t/pch-dir -Xcc -Xclang -Xcc -fallow-pcm-with-compiler-errors -Xcc -Xclang -Xcc -fmodule-format=raw %t/use.swift -Xcc -I%t/inner.hmap
 // RUN: ls %t/pch-dir/*.pch | count 1
 
 //--- bridging-header.h
-@import DoesNotExist;
+#include "inner.h"
 
 struct SomeTy {
   int a;
 };
 
+//--- inner/inner.h
+struct InnerTy {
+  int b;
+};
+
+//--- hmap.json
+{
+  "mappings": {
+    "inner.h": "TEST_DIR/inner/inner.h"
+  }
+}
+
 //--- use.swift
-func use(s: SomeTy) {}
+func use(s: SomeTy, s2: InnerTy) {}
+// MISSING_HMAP-NOT: cannot find type 'SomeTy' in scope
+// MISSING_HMAP: cannot find type 'InnerTy' in scope
+// MISSING_HMAP-NOT: cannot find type 'SomeTy' in scope