Fix crash when handling an argument parsing-related warning.

Summary: Don't crash on warnings coming before the translation unit starts.

Reviewers: klimek, djasper

Reviewed By: djasper

CC: cfe-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D2676

llvm-svn: 200702

clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.cpp

@@ -82,7 +82,9 @@ void ClangTidyDiagnosticConsumer::HandleDiagnostic(
   // FIXME: Demultiplex diagnostics.
   // FIXME: Ensure that we don't get notes from user code related to errors
   // from non-user code.
-  if (Diags->getSourceManager().isInSystemHeader(Info.getLocation()))
+  // Let argument parsing-related warnings through.
+  if (Diags->hasSourceManager() &&
+      Diags->getSourceManager().isInSystemHeader(Info.getLocation()))
     return;
   if (DiagLevel != DiagnosticsEngine::Note) {
     Errors.push_back(

clang-tools-extra/test/clang-tidy/diagnostic.cpp

@@ -0,0 +1,5 @@
+// RUN: grep -Ev "// *[A-Z-]+:" %s > %t.cpp
+// RUN: clang-tidy %t.cpp -- -fan-unknown-option > %t2.cpp
+// RUN: FileCheck -input-file=%t2.cpp %s
+
+// CHECK: warning: unknown argument: '-fan-unknown-option'