On 7/7/25 4:52 PM, Marek Polacek wrote:
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?-- >8 -- This patch is an attempt to implement P2036R3 along with P2579R0, fixing build breakages caused by P2036R3. The simplest example is: auto counter1 = [j=0]() mutable -> decltype(j) { return j++; }; which currently doesn't compile because the 'j' in the capture isn't visible in the trailing return type. With these proposals, the 'j' will be in a lambda scope which spans the trailing return type, so this test will compile. This oughtn't be difficult but decltype and other issues made this patch much more challenging. We have to push the explicit captures before going into _lambda_declarator_opt because that is what parses the trailing return type. Yet we can't build any captures until after _lambda_body -> start_lambda_function which creates the lambda's operator(), without which we can't build a proxy, but _lambda_body happens only after parsing the declarator. This patch works around it by creating a fake operator() in make_dummy_lambda_op.
I was thinking that we could build the real operator() earlier, before the trailing return type, so that it's there for the above uses, and then splice in the trailing return type to the already-built function declaration, perhaps with apply_deduced_return_type.
Jason
