Sema: Don't crash when trying to emit a warning for a duplicate value in an invalid enum.

Fixes PR15693. A null check on a pointer returned from cast<> is a very dubious
construct, do we have a checker for this somewhere?

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@178975 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 10 insertions, 1 deletions

diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 84d992c878..c8a5d932e7 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -11538,7 +11538,7 @@ static void CheckForDuplicateEnumValues(Sema &S, Decl **Elements,
   // Populate the EnumMap with all values represented by enum constants without
   // an initialier.
   for (unsigned i = 0; i < NumElements; ++i) {
-    EnumConstantDecl *ECD = cast<EnumConstantDecl>(Elements[i]);
+    EnumConstantDecl *ECD = cast_or_null<EnumConstantDecl>(Elements[i]);
 
     // Null EnumConstantDecl means a previous diagnostic has been emitted for
     // this constant.  Skip this enum since it may be ill-formed.
diff --git a/test/Sema/warn-duplicate-enum.c b/test/Sema/warn-duplicate-enum.c
index 239f6f1995..f108b3aa6c 100644
--- a/test/Sema/warn-duplicate-enum.c
+++ b/test/Sema/warn-duplicate-enum.c
@@ -90,3 +90,12 @@ enum {
   NMax = N2,
   NCount = NMax + 1
 };
+
+// PR15693
+enum enum1 {
+  VALUE // expected-note{{previous definition is here}}
+};
+
+enum enum2 {
+  VALUE // expected-error{{redefinition of enumerator 'VALUE'}}
+};