Switch a cast to a dyn_cast and check the pointer before using. Fixes a crash

in the following code:

void test4(bool (&x)(void)) {
  while (x);
}

llvm-svn: 145918

clang/lib/Sema/SemaChecking.cpp

@@ -3771,12 +3771,13 @@ void CheckImplicitConversion(Sema &S, Expr *E, QualType T,
       }
 
       if (D && !D->isWeak()) {
-        FunctionDecl* F = cast<FunctionDecl>(D);
+        if (FunctionDecl* F = dyn_cast<FunctionDecl>(D)) {
           S.Diag(E->getExprLoc(), diag::warn_impcast_function_to_bool)
             << F << E->getSourceRange() << SourceRange(CC);
           return;
         }
       }
+    }
     return; // Other casts to bool are not checked.
   }
 

clang/test/SemaCXX/condition.cpp

@@ -52,3 +52,7 @@ void test3() {
   if (test3) // expected-warning {{address of function 'test3' will always evaluate to 'true'}}
     (void) 0;
 }
+
+void test4(bool (&x)(void)) {
+  while (x);
+}