[AST][RecoveryExpr] Fix a crash on a field decl with invalid type.

[hokein]

Summary

The field decl (in the testcase) was still valid, which results in a
valid RecordDecl, it led to crash when performing struct layout,
and computing struct size etc.

clang/lib/Sema/SemaDecl.cpp

FieldDecl *Sema::CheckFieldDecl(DeclarationName Name, QualType T,
                                 AccessSpecifier AS, NamedDecl *PrevDecl,
                                 Declarator *D) {
   IdentifierInfo *II = Name.getAsIdentifierInfo();
   bool InvalidDecl = false;
   if (D) InvalidDecl = D->isInvalidType();
 
   // If we receive a broken type, recover by assuming 'int' and
   // marking this declaration as invalid.
-  if (T.isNull()) {
+  if (T.isNull() || T->containsErrors()) {
     InvalidDecl = true;
     T = Context.IntTy;
   }
 
   QualType EltTy = Context.getBaseElementType(T);
   if (!EltTy->isDependentType() && !EltTy->containsErrors()) {
     if (RequireCompleteSizedType(Loc, EltTy,
                                  diag::err_field_incomplete_or_sizeless)) {

clang/test/Sema/invalid-member.cpp

 // RUN: %clang_cc1 -verify -fsyntax-only -fno-recovery-ast %s
 // RUN: %clang_cc1 -verify -fsyntax-only -frecovery-ast %s
 
 void foo(); // expected-note 2{{requires 0 arguments}}
 class X {
   decltype(foo(42)) invalid; // expected-error {{no matching function}}
 };
 // Should be able to evaluate sizeof without crashing.
 static_assert(sizeof(X) == 1, "No valid members");
 
 class Y {
   typeof(foo(42)) invalid; // expected-error {{no matching function}}
 };
 // Should be able to evaluate sizeof without crashing.
 static_assert(sizeof(Y) == 1, "No valid members");
+
+class Z {
+  int array[sizeof(invalid())]; // expected-error {{use of undeclared identifier}}
+};
+// Should be able to evaluate sizeof without crashing.
+static_assert(sizeof(Z) == 1, "No valid members");