[clang] Treat variable-length array of incomplete element type as

incomplete type.

Differential Revision: https://reviews.llvm.org/D99165

clang/lib/AST/Type.cpp

@@ -2229,10 +2229,11 @@ bool Type::isIncompleteType(NamedDecl **Def) const {
     return !Rec->isCompleteDefinition();
   }
   case ConstantArray:
+  case VariableArray:
     // An array is incomplete if its element type is incomplete
     // (C++ [dcl.array]p1).
-    // We don't handle variable arrays (they're not allowed in C++) or
-    // dependent-sized arrays (dependent types are never treated as incomplete).
+    // We don't handle dependent-sized arrays (dependent types are never treated
+    // as incomplete).
     return cast<ArrayType>(CanonicalType)->getElementType()
              ->isIncompleteType(Def);
   case IncompleteArray:

clang/test/SemaCXX/cxx0x-initializer-aggregates.cpp

@@ -133,3 +133,10 @@ namespace array_addressof {
 namespace PR24816 {
   struct { int i; } ne = {{0, 1}}; // expected-error{{excess elements in scalar initializer}}
 }
+
+namespace no_crash {
+class Foo; // expected-note {{forward declaration}}
+void test(int size) {
+  Foo array[size] = {0}; // expected-error {{variable has incomplete type}}
+}
+}