[Sema] Avoid instantiating templates only when UncompilableErrorOccurred

and FatalErrorOccurred are both set.

This fixes a crash that occurs when a warning promoted to a fatal error
leaves the AST in an incomplete state, and then later CFG analysis is
run on the incomplete AST.

rdar://problem/28558923

Differential Revision: https://reviews.llvm.org/D26166

llvm-svn: 285923

1 files changed, 5 insertions, 3 deletions

diff --git a/clang/lib/Sema/SemaTemplateInstantiate.cpp b/clang/lib/Sema/SemaTemplateInstantiate.cpp
index b715c13b077..6e715d25b4d 100644
--- a/clang/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiate.cpp
@@ -209,9 +209,11 @@ Sema::InstantiatingTemplate::InstantiatingTemplate(
     sema::TemplateDeductionInfo *DeductionInfo)
     : SemaRef(SemaRef), SavedInNonInstantiationSFINAEContext(
                             SemaRef.InNonInstantiationSFINAEContext) {
-  // Don't allow further instantiation if a fatal error has occcured.  Any
-  // diagnostics we might have raised will not be visible.
-  if (SemaRef.Diags.hasFatalErrorOccurred()) {
+  // Don't allow further instantiation if a fatal error and an uncompilable
+  // error have occcured. Any diagnostics we might have raised will not be
+  // visible, and we do not need to construct a correct AST.
+  if (SemaRef.Diags.hasFatalErrorOccurred() &&
+      SemaRef.Diags.hasUncompilableErrorOccurred()) {
     Invalid = true;
     return;
   }