[MSVC] Fix check for wchar_t type in case of -fno-wchar

[DmitryPolukhin]

Summary

The example below should work identically with and without compiler native wchar_t support.

void foo(wchar_t * t = L"");

[rnk]

lgtm

test/SemaCXX/no-wchar.cpp

12 ↗

(On Diff #53542)

Can you add some negative tests like these:

short *p1 = L""; // error
int *p2 = L""; // error

Even if they don't make it into IsStringLiteralToNonConstPointerConversion, it's nice to test around things a bit.

[DmitryPolukhin]

I added few more negative tests. Thank you for the review!

cfe/trunk/lib/Sema/SemaExprCXX.cpp

if (const PointerType *ToPtrType = ToType->getAs<PointerType>())
             case StringLiteral::UTF16:
             case StringLiteral::UTF32:
               // We don't allow UTF literals to be implicitly converted
               break;
             case StringLiteral::Ascii:
               return (ToPointeeType->getKind() == BuiltinType::Char_U ||
                       ToPointeeType->getKind() == BuiltinType::Char_S);
             case StringLiteral::Wide:
-              return ToPointeeType->isWideCharType();
+              return Context.typesAreCompatible(Context.getWideCharType(),
+                                                QualType(ToPointeeType, 0));
           }
         }
       }
 
   return false;
 }
 
 static ExprResult BuildCXXCastArgument(Sema &S,

cfe/trunk/test/SemaCXX/no-wchar.cpp

 // RUN: %clang_cc1 -triple i386-pc-win32 -fsyntax-only -fno-wchar -verify %s
 wchar_t x; // expected-error {{unknown type name 'wchar_t'}}
 
 typedef unsigned short wchar_t;
 void foo(const wchar_t* x);
 
 void bar() {
   foo(L"wide string literal");
 }
+
+void foo1(wchar_t * t = L"");
+// expected-warning@-1 {{conversion from string literal to 'wchar_t *' (aka 'unsigned short *') is deprecated}}
+
+short *a = L"";
+// expected-error@-1 {{cannot initialize a variable of type 'short *' with an lvalue of type 'const unsigned short [1]'}}
+char *b = L"";
+// expected-error@-1 {{cannot initialize a variable of type 'char *' with an lvalue of type 'const unsigned short [1]'}}
+
+// NOTE: MSVC allows deprecated conversion in conditional expression if at least
+// one of the operand is a string literal but Clang doesn't allow it.
+wchar_t *c = true ? L"a" : L"";
+// expected-error@-1 {{cannot initialize a variable of type 'wchar_t *' (aka 'unsigned short *') with}}
+
+const wchar_t *d1 = 0;
+const wchar_t *d2 = 0;
+wchar_t *d = true ? d1 : d2;
+// expected-error@-1 {{cannot initialize a variable of type 'wchar_t *' (aka 'unsigned short *') with}}
+
+wchar_t* e = (const wchar_t*)L"";
+// expected-error@-1 {{cannot initialize a variable of type 'wchar_t *' (aka 'unsigned short *') with an rvalue of type 'const wchar_t *' (aka 'const unsigned short *')}}