https://gcc.gnu.org/g:4d02f20772f170b78491769a78086c92de127f95
commit r16-6352-g4d02f20772f170b78491769a78086c92de127f95 Author: Egas Ribeiro <[email protected]> Date: Fri Dec 19 16:58:58 2025 +0000 c++: Fix ICE with lambdas combining explicit and implicit template params [PR117518] When a lambda with explicit template parameters like []<int> also has implicit template parameters from auto, and is used as a default template argument, processing_template_parmlist remained set from the outer template context. This caused function_being_declared_is_template_p to incorrectly return false, leading synthesize_implicit_template_parm to create a new template scope instead of extending the existing one, resulting in a binding level mismatch and an ICE in poplevel_class. Fix by clearing processing_template_parmlist in cp_parser_lambda_expression alongside the other parser state save/restore operations. PR c++/117518 gcc/cp/ChangeLog: * parser.cc (cp_parser_lambda_expression): Clear processing_template_parmlist when parsing lambda body. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/lambda-targ19.C: New test. Signed-off-by: Egas Ribeiro <[email protected]> Reviewed-by: Jason Merrill <[email protected]> Diff: --- gcc/cp/parser.cc | 2 ++ gcc/testsuite/g++.dg/cpp2a/lambda-targ19.C | 4 ++++ 2 files changed, 6 insertions(+) diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc index b3bf0703d3d2..26da789f8218 100644 --- a/gcc/cp/parser.cc +++ b/gcc/cp/parser.cc @@ -12043,6 +12043,8 @@ cp_parser_lambda_expression (cp_parser* parser, bool saved_omp_array_section_p = parser->omp_array_section_p; bool saved_in_targ = parser->in_template_argument_list_p; bool saved_in_declarator_p = parser->in_declarator_p; + auto parmlist_sentinel + = make_temp_override (processing_template_parmlist, 0); parser->num_template_parameter_lists = 0; parser->in_statement = 0; diff --git a/gcc/testsuite/g++.dg/cpp2a/lambda-targ19.C b/gcc/testsuite/g++.dg/cpp2a/lambda-targ19.C new file mode 100644 index 000000000000..d02f6d6a3a38 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/lambda-targ19.C @@ -0,0 +1,4 @@ +// { dg-do compile { target c++20 } } +// PR c++/117518 +template <auto = []<int> (auto) {}> int x; +int y = x<>;
