C++ PATCH for c++/86499, non-local lambda with a capture-default

[Marek Polacek]

This PR complains about us accepting a lambda with a capture-default
at file scope, which seems to be forbidden.  This patch disallows
such a use.  clang gives an error, so I did the same, but maybe we
only want a pedwarn.

Bootstrapped/regtested on x86_64-linux, ok for trunk?

2018-08-13  Marek Polacek  <pola...@redhat.com>

        PR c++/86499
        * parser.c (cp_parser_lambda_introducer): Give error if a non-local
        lambda has a capture-default.

        * g++.dg/cpp0x/lambda/lambda-non-local.C: New test.
        * g++.dg/cpp0x/lambda/lambda-this10.C: Adjust dg-error.

diff --git gcc/cp/parser.c gcc/cp/parser.c
index 8cfcd150705..6a760136f99 100644
--- gcc/cp/parser.c
+++ gcc/cp/parser.c
@@ -10280,6 +10280,9 @@ cp_parser_lambda_introducer (cp_parser* parser, tree 
lambda_expr)
     {
       cp_lexer_consume_token (parser->lexer);
       first = false;
+
+      if (!(at_function_scope_p () || at_class_scope_p ()))
+       error ("non-local lambda expression cannot have a capture-default");
     }
 
   while (cp_lexer_next_token_is_not (parser->lexer, CPP_CLOSE_SQUARE))
diff --git gcc/testsuite/g++.dg/cpp0x/lambda/lambda-non-local.C 
gcc/testsuite/g++.dg/cpp0x/lambda/lambda-non-local.C
index e69de29bb2d..005f8f3888b 100644
--- gcc/testsuite/g++.dg/cpp0x/lambda/lambda-non-local.C
+++ gcc/testsuite/g++.dg/cpp0x/lambda/lambda-non-local.C
@@ -0,0 +1,10 @@
+// PR c++/86499
+// { dg-do compile { target c++11 } }
+
+auto l1 = [=]{}; // { dg-error "non-local lambda expression cannot have a 
capture-default" }
+auto l2 = [&]{}; // { dg-error "non-local lambda expression cannot have a 
capture-default" }
+
+namespace {
+  auto l3 = [=]{}; // { dg-error "non-local lambda expression cannot have a 
capture-default" }
+  auto l4 = [&]{}; // { dg-error "non-local lambda expression cannot have a 
capture-default" }
+}
diff --git gcc/testsuite/g++.dg/cpp0x/lambda/lambda-this10.C 
gcc/testsuite/g++.dg/cpp0x/lambda/lambda-this10.C
index b4b8e7201aa..e8e94771ef0 100644
--- gcc/testsuite/g++.dg/cpp0x/lambda/lambda-this10.C
+++ gcc/testsuite/g++.dg/cpp0x/lambda/lambda-this10.C
@@ -1,4 +1,4 @@
 // PR c++/54383
 // { dg-do compile { target c++11 } }
 
-auto foo = [&](int a) { return a > this->b; }; // { dg-error "this" }
+auto foo = [&](int a) { return a > this->b; }; // { dg-error "non-local|this" }