re PR c++/79133 (lambda capture shadowing parameter & decltype confusion)

PR c++/79133

gcc/cp/

PR c++/79133
* name-lookup.c (check_local_shadow): Reject captures and parameters
with the same name.

testsuite/

PR c++/79133
* g++.dg/cpp0x/lambda/lambda-shadow3.C: New.
* g++.dg/cpp1y/lambda-generic-variadic18.C: Likewise.

From-SVN: r263357

gcc/cp/ChangeLog

+2018-08-07  Ville Voutilainen  <ville.voutilainen@gmail.com>
+
+	PR c++/79133
+	* name-lookup.c (check_local_shadow): Reject captures and parameters
+	with the same name.
+
 2018-08-06  Marek Polacek  <polacek@redhat.com>
 
 	PR c++/86767

gcc/cp/name-lookup.c

@@ -2640,13 +2640,29 @@ check_local_shadow (tree decl)
 		  || TREE_CODE (decl) == TYPE_DECL)))
       && DECL_FUNCTION_SCOPE_P (old)
       && (!DECL_ARTIFICIAL (decl)
+	  || is_capture_proxy (decl)
 	  || DECL_IMPLICIT_TYPEDEF_P (decl)
 	  || (VAR_P (decl) && DECL_ANON_UNION_VAR_P (decl))))
     {
       /* DECL shadows a local thing possibly of interest.  */
 
+      /* DR 2211: check that captures and parameters
+	 do not have the same name. */
+      if (is_capture_proxy (decl))
+	{
+	  if (current_lambda_expr ()
+	      && DECL_CONTEXT (old) == lambda_function (current_lambda_expr ())
+	      && TREE_CODE (old) == PARM_DECL
+	      && DECL_NAME (decl) != this_identifier)
+	    {
+	      error_at (DECL_SOURCE_LOCATION (old),
+			"lambda parameter %qD "
+			"previously declared as a capture", old);
+	    }
+	  return;
+	}
       /* Don't complain if it's from an enclosing function.  */
-      if (DECL_CONTEXT (old) == current_function_decl
+      else if (DECL_CONTEXT (old) == current_function_decl
 	  && TREE_CODE (decl) != PARM_DECL
 	  && TREE_CODE (old) == PARM_DECL)
 	{

gcc/testsuite/g++.dg/cpp0x/lambda/lambda-shadow3.C

+// { dg-do compile { target c++11 } }
+
+int main() {
+  int x = 42;
+  auto lambda = [x](int x) {}; // { dg-error "previously declared as a capture" }
+}

gcc/testsuite/g++.dg/cpp1y/lambda-generic-variadic18.C

+// { dg-do compile { target c++14 } }
+
+int main() {
+  int x = 42;
+  auto lambda2 = [x=x](int x) {}; // { dg-error "previously declared as a capture" }
+  auto lambda3 = [x](auto... x) {}; // { dg-error "previously declared as a capture" }
+  auto lambda4 = [](auto... x) {
+    auto lambda5 = [x...](auto... x) {};  // { dg-error "previously declared as a capture" }
+    auto lambda6 = [x...](int x) {};  // { dg-error "previously declared as a capture" }
+  };
+}