1 files changed, 22 insertions, 0 deletions
diff --git a/clang/lib/Parse/ParseExpr.cpp b/clang/lib/Parse/ParseExpr.cpp
index 847b074d5c8..582721cf40f 100644
--- a/clang/lib/Parse/ParseExpr.cpp
+++ b/clang/lib/Parse/ParseExpr.cpp
@@ -1589,6 +1589,28 @@ Parser::ParseExprAfterUnaryExprOrTypeTrait(const Token &OpTok,
 
   // If the operand doesn't start with an '(', it must be an expression.
   if (Tok.isNot(tok::l_paren)) {
+    // If construct allows a form without parenthesis, user may forget to put
+    // pathenthesis around type name.
+    if (OpTok.is(tok::kw_sizeof)  || OpTok.is(tok::kw___alignof) ||
+        OpTok.is(tok::kw_alignof) || OpTok.is(tok::kw__Alignof)) {
+      bool isAmbiguousTypeId;
+      if (isTypeIdInParens(isAmbiguousTypeId)) {
+        DeclSpec DS(AttrFactory);
+        ParseSpecifierQualifierList(DS);
+        Declarator DeclaratorInfo(DS, Declarator::TypeNameContext);
+        ParseDeclarator(DeclaratorInfo);
+
+        SourceLocation LParenLoc = PP.getLocForEndOfToken(OpTok.getLocation());
+        SourceLocation RParenLoc = PP.getLocForEndOfToken(PrevTokLocation);
+        Diag(LParenLoc, diag::err_missed_parenthesis_around_typename)
+          << OpTok.getName()
+          << FixItHint::CreateInsertion(LParenLoc, "(")
+          << FixItHint::CreateInsertion(RParenLoc, ")");
+        isCastExpr = true;
+        return ExprEmpty();
+      }
+    }
+
     isCastExpr = false;
     if (OpTok.is(tok::kw_typeof) && !getLangOpts().CPlusPlus) {
       Diag(Tok,diag::err_expected_lparen_after_id) << OpTok.getIdentifierInfo();