Support constant expression evaluation for wchar_t versions of simple string
functions, in order to support constexpr std::char_traits<wchar_t>.

llvm-svn: 288193
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index 26c7938..62d9b65 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -8554,6 +8554,10 @@
     assert(HowLong == 0 && !Signed && !Unsigned && "Bad modifiers for 'z'!");
     Type = Context.getSizeType();
     break;
+  case 'w':  // wchar_t.
+    assert(HowLong == 0 && !Signed && !Unsigned && "Bad modifiers for 'w'!");
+    Type = Context.getWideCharType();
+    break;
   case 'F':
     Type = Context.getCFConstantStringType();
     break;