c++: Look through capture proxy from outer lambda instead of erroring out [PR110584]

We've been rejecting this valid code since r8-4571:

=== cut here ===
void foo (float);
int main () {
  constexpr float x = 0;
  (void) [&] () {
    foo (x);
    (void) [] () {
      foo (x);
    };
  };
}
=== cut here ===

The problem is that when processing X in the inner lambda,
process_outer_var_ref errors out even though it does find the constant
capture from the enclosing lambda.

This patch makes sure that process_outer_var_ref properly looks through
normal capture proxies, if any.

	PR c++/110584

gcc/cp/ChangeLog:

	* cp-tree.h (strip_normal_capture_proxy): Declare.
	* lambda.cc (strip_normal_capture_proxy): New function to look
	through normal capture proxies.
	(build_capture_proxy): Use it.
	* semantics.cc (process_outer_var_ref): Likewise.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/lambda/lambda-nested10.C: New test.

0 files changed, 0 insertions, 0 deletions