Sema: Cleanup and improve string-plus-char checking.

Patch by Anders Rönnholm

llvm-svn: 224268

clang/lib/Sema/SemaExpr.cpp

@@ -7312,13 +7312,13 @@ static void diagnoseStringPlusInt(Sema &Self, SourceLocation OpLoc,
 /// \brief Emit a warning when adding a char literal to a string.
 static void diagnoseStringPlusChar(Sema &Self, SourceLocation OpLoc,
                                    Expr *LHSExpr, Expr *RHSExpr) {
-  const DeclRefExpr *StringRefExpr =
-      dyn_cast<DeclRefExpr>(LHSExpr->IgnoreImpCasts());
+  const Expr *StringRefExpr = LHSExpr;
   const CharacterLiteral *CharExpr =
       dyn_cast<CharacterLiteral>(RHSExpr->IgnoreImpCasts());
-  if (!StringRefExpr) {
-    StringRefExpr = dyn_cast<DeclRefExpr>(RHSExpr->IgnoreImpCasts());
+
+  if (!CharExpr) {
     CharExpr = dyn_cast<CharacterLiteral>(LHSExpr->IgnoreImpCasts());
+    StringRefExpr = RHSExpr;
   }
 
   if (!CharExpr || !StringRefExpr)

clang/test/Sema/string-plus-char.c

@@ -1,5 +1,11 @@
 // RUN: %clang_cc1 -fsyntax-only -verify %s
 
+struct AB{const char *a; const char*b;};
+
+const char *foo(const struct AB *ab) {
+  return ab->a + 'b'; // expected-warning {{adding 'char' to a string pointer does not append to the string}} expected-note {{use array indexing to silence this warning}}
+}
+
 void f(const char *s) {
   char *str = 0;
   char *str2 = str + 'c'; // expected-warning {{adding 'char' to a string pointer does not append to the string}} expected-note {{use array indexing to silence this warning}}
@@ -8,6 +14,15 @@ void f(const char *s) {
 
   str = 'c' + str;// expected-warning {{adding 'char' to a string pointer does not append to the string}} expected-note {{use array indexing to silence this warning}}
 
+  char strArr[] = "foo";
+  str = strArr + 'c'; // expected-warning {{adding 'char' to a string pointer does not append to the string}} expected-note {{use array indexing to silence this warning}}
+  char *strArr2[] = {"ac","dc"};
+  str = strArr2[0] + 'c'; // expected-warning {{adding 'char' to a string pointer does not append to the string}} expected-note {{use array indexing to silence this warning}}
+
+
+  struct AB ab;
+  constStr = foo(&ab) + 'c'; // expected-warning {{adding 'char' to a string pointer does not append to the string}} expected-note {{use array indexing to silence this warning}}
+
   // no-warning
   char c = 'c';
   str = str + c;