Revert "[Sema] Suppress -Wchar-subscripts if the index is a literal char"

This reverts commit 7adab7719e.

clang/lib/Sema/SemaExpr.cpp

@@ -4741,8 +4741,7 @@ Sema::CreateBuiltinArraySubscriptExpr(Expr *Base, SourceLocation LLoc,
 
   if ((IndexExpr->getType()->isSpecificBuiltinType(BuiltinType::Char_S) ||
        IndexExpr->getType()->isSpecificBuiltinType(BuiltinType::Char_U))
-         && !IndexExpr->isTypeDependent()
-         && !isa<CharacterLiteral>(IndexExpr))
+         && !IndexExpr->isTypeDependent())
     Diag(LLoc, diag::warn_subscript_is_char) << IndexExpr->getSourceRange();
 
   // C99 6.5.2.1p1: "shall have type "pointer to *object* type". Similarly,

clang/test/SemaCXX/warn-char-subscripts.cpp

@@ -14,19 +14,6 @@ void t2() {
   int val = subscript[array]; // expected-warning{{array subscript is of type 'char'}}
 }
 
-void t3() {
-  int array[50] = { 0 };
-  int val = array[' ']; // no warning, subscript is a literal
-}
-void t4() {
-  int array[50] = { 0 };
-  int val = '('[array]; // no warning, subscript is a literal
-}
-void t5() {
-  int array[50] = { 0 };
-  int val = array['\x11']; // no warning, subscript is a literal
-}
-
 void test() {
   t1<char>(); // expected-note {{in instantiation of function template specialization 't1<char>' requested here}}
   t2<char>(); // expected-note {{in instantiation of function template specialization 't2<char>' requested here}}