[libclang] Fix CXTranslationUnit_KeepGoing

[nik]

Summary

Since

commit 56f548bbbb7e4387a69708f70724d00e9e076153
[modules] Round-trip -Werror flag through explicit module build.

the behavior of CXTranslationUnit_KeepGoing changed:
Unresolved #includes are fatal errors again. As a consequence, some
templates are not instantiated and lead to confusing errors.

Revert to the old behavior: With CXTranslationUnit_KeepGoing fatal
errors are mapped to errors.

[nik]

Fixed minor typo.

include/clang/Basic/Diagnostic.h

public:
   /// Represents on argument value, which is a union discriminated
   /// by ArgumentKind, with a value.
   using ArgumentValue = std::pair<ArgumentKind, intptr_t>;
 
 private:
   // Used by __extension__
   unsigned char AllExtensionsSilenced = 0;
 
-  // Suppress diagnostics after a fatal error?
-  bool SuppressAfterFatalError = true;
+  // Treat fatal errors like errors.
+  bool FatalsAsError = false;
 
   // Suppress all diagnostics.
   bool SuppressAllDiagnostics = false;
 
   // Elide common types of templates.
   bool ElideType = true;
 
   // Print a tree when comparing templates.
public:
   bool getWarningsAsErrors() const {
     return GetCurDiagState()->WarningsAsErrors;
   }
 
   /// When set to true, any error reported is made a fatal error.
   void setErrorsAsFatal(bool Val) { GetCurDiagState()->ErrorsAsFatal = Val; }
   bool getErrorsAsFatal() const { return GetCurDiagState()->ErrorsAsFatal; }
 
-  /// When set to true (the default), suppress further diagnostics after
-  /// a fatal error.
-  void setSuppressAfterFatalError(bool Val) { SuppressAfterFatalError = Val; }
+  /// \brief When set to true, any fatal error reported is made an error.
+  ///
+  /// This setting takes precedence over the setErrorsAsFatal setting above.
+  void setFatalsAsError(bool Val) { FatalsAsError = Val; }
+  bool getFatalsAsError() const { return FatalsAsError; }
 
   /// When set to true mask warnings that come from system headers.
   void setSuppressSystemWarnings(bool Val) {
     GetCurDiagState()->SuppressSystemWarnings = Val;
   }
   bool getSuppressSystemWarnings() const {
     return GetCurDiagState()->SuppressSystemWarnings;
   }

lib/Basic/DiagnosticIDs.cpp

DiagnosticIDs::getDiagnosticSeverity(unsigned DiagID, SourceLocation Loc,
 
   // If -Wfatal-errors is enabled, map errors to fatal unless explicitly
   // disabled.
   if (Result == diag::Severity::Error) {
     if (State->ErrorsAsFatal && !Mapping.hasNoErrorAsFatal())
       Result = diag::Severity::Fatal;
   }
 
+  // If explicitly requested, map fatal errors to errors.
+  if (Result == diag::Severity::Fatal &&
+      Diag.CurDiagID != diag::fatal_too_many_errors && Diag.FatalsAsError)
+    Result = diag::Severity::Error;
+
   // Custom diagnostics always are emitted in system headers.
   bool ShowInSystemHeader =
       !GetDiagInfo(DiagID) || GetDiagInfo(DiagID)->WarnShowInSystemHeader;
 
   // If we are in a system header, we ignore it. We look at the diagnostic class
   // because we also want to ignore extensions and warnings in -Werror and
   // -pedantic-errors modes, which *map* warnings/extensions to errors.
   if (State->SuppressSystemWarnings && !ShowInSystemHeader && Loc.isValid() &&
if (DiagLevel != DiagnosticIDs::Note) {
     if (Diag.LastDiagLevel == DiagnosticIDs::Fatal)
       Diag.FatalErrorOccurred = true;
 
     Diag.LastDiagLevel = DiagLevel;
   }
 
   // If a fatal error has already been emitted, silence all subsequent
   // diagnostics.
-  if (Diag.FatalErrorOccurred && Diag.SuppressAfterFatalError) {
+  if (Diag.FatalErrorOccurred) {
     if (DiagLevel >= DiagnosticIDs::Error &&
         Diag.Client->IncludeInDiagnosticCounts()) {
       ++Diag.NumErrors;
     }
 
     return false;
   }
 

test/Index/Inputs/keep-going-template-instantiations.h

+template<typename T, T v> struct c {};
+using d = c<bool, false>;
+struct foo : public d {};

test/Index/keep-going-template-instantiations.cpp

+#include "missing.h"
+#include <keep-going-template-instantiations.h>
+
+// RUN: env CINDEXTEST_KEEP_GOING=1 c-index-test -test-load-source none -I%S/Inputs %s 2>&1 | FileCheck %s
+// CHECK-NOT: error: expected class name

test/Index/keep-going.cpp

 // CHECK: C++ base class specifier=A<int>:4:7 [access=public isVirtual=false] [type=A<int>] [typekind=Unexposed] [templateargs/1= [type=int] [typekind=Int]] [canonicaltype=A<int>] [canonicaltypekind=Record] [canonicaltemplateargs/1= [type=int] [typekind=Int]] [isPOD=0] [nbFields=1]
 // CHECK: TemplateRef=A:4:7 [type=] [typekind=Invalid] [isPOD=0]
 // CHECK: ClassDecl=C:10:7 (Definition) [type=C] [typekind=Record] [isPOD=0]
 // CHECK: C++ base class specifier=A<float>:4:7 [access=public isVirtual=false] [type=A<float>] [typekind=Unexposed] [templateargs/1= [type=float] [typekind=Float]] [canonicaltype=A<float>] [canonicaltypekind=Record] [canonicaltemplateargs/1= [type=float] [typekind=Float]] [isPOD=0] [nbFields=1]
 // CHECK: TemplateRef=A:4:7 [type=] [typekind=Invalid] [isPOD=0]
 
 // CHECK-KEEP-GOING-ONLY: VarDecl=global_var:1:12 [type=int] [typekind=Int] [isPOD=1]
 
-// CHECK-DIAG: keep-going.cpp:1:10: fatal error: 'missing1.h' file not found
-// CHECK-DIAG: keep-going.cpp:8:10: fatal error: 'missing2.h' file not found
+// CHECK-DIAG: keep-going.cpp:1:10: error: 'missing1.h' file not found
+// CHECK-DIAG: keep-going.cpp:8:10: error: 'missing2.h' file not found

tools/libclang/CIndex.cpp

SkipFunctionBodies =
             : SkipFunctionBodiesScope::PreambleAndMainFile;
   }
 
   // Configure the diagnostics.
   IntrusiveRefCntPtr<DiagnosticsEngine>
     Diags(CompilerInstance::createDiagnostics(new DiagnosticOptions));
 
   if (options & CXTranslationUnit_KeepGoing)
-    Diags->setSuppressAfterFatalError(false);
+    Diags->setFatalsAsError(true);
 
   // Recover resources if we crash before exiting this function.
   llvm::CrashRecoveryContextCleanupRegistrar<DiagnosticsEngine,
     llvm::CrashRecoveryContextReleaseRefCleanup<DiagnosticsEngine> >
     DiagCleanup(Diags.get());
 
   std::unique_ptr<std::vector<ASTUnit::RemappedFile>> RemappedFiles(
       new std::vector<ASTUnit::RemappedFile>());

unittests/Basic/DiagnosticTest.cpp

TEST(DiagnosticTest, suppressAndTrap) {
   }
 
   EXPECT_FALSE(Diags.hasErrorOccurred());
   EXPECT_FALSE(Diags.hasFatalErrorOccurred());
   EXPECT_FALSE(Diags.hasUncompilableErrorOccurred());
   EXPECT_FALSE(Diags.hasUnrecoverableErrorOccurred());
 }
 
-// Check that SuppressAfterFatalError works as intended
-TEST(DiagnosticTest, suppressAfterFatalError) {
-  for (unsigned Suppress = 0; Suppress != 2; ++Suppress) {
+// Check that FatalsAsError works as intended
+TEST(DiagnosticTest, fatalsAsError) {
+  for (unsigned FatalsAsError = 0; FatalsAsError != 2; ++FatalsAsError) {
     DiagnosticsEngine Diags(new DiagnosticIDs(),
                             new DiagnosticOptions,
                             new IgnoringDiagConsumer());
-    Diags.setSuppressAfterFatalError(Suppress);
+    Diags.setFatalsAsError(FatalsAsError);
 
     // Diag that would set UnrecoverableErrorOccurred and ErrorOccurred.
     Diags.Report(diag::err_cannot_open_file) << "file" << "error";
 
     // Diag that would set FatalErrorOccurred
     // (via non-note following a fatal error).
     Diags.Report(diag::warn_mt_message) << "warning";
 
     EXPECT_TRUE(Diags.hasErrorOccurred());
-    EXPECT_TRUE(Diags.hasFatalErrorOccurred());
+    EXPECT_EQ(Diags.hasFatalErrorOccurred(), FatalsAsError ? 0u : 1u);
     EXPECT_TRUE(Diags.hasUncompilableErrorOccurred());
     EXPECT_TRUE(Diags.hasUnrecoverableErrorOccurred());
 
     // The warning should be emitted and counted only if we're not suppressing
     // after fatal errors.
-    EXPECT_EQ(Diags.getNumWarnings(), Suppress ? 0u : 1u);
+    EXPECT_EQ(Diags.getNumWarnings(), FatalsAsError);
   }
 }
 
 TEST(DiagnosticTest, diagnosticError) {
   DiagnosticsEngine Diags(new DiagnosticIDs(), new DiagnosticOptions,
                           new IgnoringDiagConsumer());
   PartialDiagnostic::StorageAllocator Alloc;
   llvm::Expected<std::pair<int, int>> Value = DiagnosticError::create(