Re: [Jiří Paleček] [PATCH][C+ +] Fix constant reference in a lambda ( PR c++/53488)

[Jason Merrill <jason at redhat dot com>]

Thanks for the patch!

> The idea of the fix is to postpone the decision whether or not to capture  later to the template instantiation.

That makes sense.  We might as well postpone all default captures to 
instantiation time, since we need to postpone some of them.

> +        /* This is a hack:
> +
> +           We absolutely need the capture list to be nonempty if the
> +           template had it nonempty, otherwise, we will have the
> +           conversion-to-function-pointer operator erroneously
> +           added. We use a dummy list with a single element that we
> +           can get rid of easily later
> +        */
> +	LAMBDA_EXPR_CAPTURE_LIST (r)
> +          = LAMBDA_EXPR_CAPTURE_LIST (t) != NULL_TREE ? tree_cons(NULL_TREE, NULL_TREE, NULL_TREE) : NULL_TREE;

I think rather than do this, we should set LAMBDA_EXPR_CAPTURE_LIST in 
instantiate_class_template_1.

Jason