https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120879
Bug ID: 120879 Summary: ICE: tree check: expected tree_vec, have identifier_node in tsubst_decl, at cp/pt.cc:15757 Product: gcc Version: 16.0 Status: UNCONFIRMED Keywords: ice-checking, ice-on-invalid-code, needs-reduction Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: rush102333 at gmail dot com Target Milestone: --- $cat test.cpp template<typename ...T> auto lambda1() { return [](auto x) { struct A : T::template X<decltype(x)>... { using T::template X<decltype(x)>::f ...; using typename T::template X<decltype(x)>::type ...; void g(int n) { f(n); } void h() { type value; } A self_member; }; return A(); }; } struct A { template<typename> template<typename> struct X { void f(int); using type = int; X self_member; }; }; void f() { lambda1<A>() (0) .g(0); } With assertion enabled: $g++ test.cpp <source>: In lambda function: <source>:9:3: error: field 'self_member' has incomplete type 'lambda1()::<lambda(auto:1)>::A' [-Wtemplate-body] 9 | A self_member; }; | ^~~~~~~~~~~ <source>:3:12: note: definition of 'struct lambda1()::<lambda(auto:1)>::A' is not complete until the closing brace 3 | struct A : T::template X<decltype(x)>... { | ^ <source>: At global scope: <source>:15:46: error: too many template-parameter-lists 15 | template<typename> template<typename> struct X { | ^ <source>: In instantiation of 'struct lambda1<A>()::<lambda(auto:1)>::A': <source>:9:16: required from 'lambda1<A>()::<lambda(auto:1)> [with auto:1 = int]' 9 | A self_member; }; | ^ <source>:24:5: required from here 23 | lambda1<A>() | ~~~~~~~~~~~~ 24 | (0) | ^~~ <source>:3:12: error: no class template named 'X' in 'struct A' 3 | struct A : T::template X<decltype(x)>... { | ^ <source>:4:43: error: no class template named 'X' in 'struct A' 4 | using T::template X<decltype(x)>::f ...; | ^~~ <source>:4:43: internal compiler error: tree check: expected tree_vec, have identifier_node in tsubst_decl, at cp/pt.cc:15757 0x2844425 diagnostic_context::diagnostic_impl(rich_location*, diagnostic_metadata const*, diagnostic_option_id, char const*, __va_list_tag (*) [1], diagnostic_t) ???:0 0x2866fc6 internal_error(char const*, ...) ???:0 0x9f8e25 tree_check_failed(tree_node const*, char const*, int, char const*, ...) ???:0 0xd4c0c4 tsubst(tree_node*, tree_node*, int, tree_node*) ???:0 0xd7a999 instantiate_class_template(tree_node*) ???:0 0xd6e87d instantiate_decl(tree_node*, bool, bool) ???:0 0xbf7843 maybe_instantiate_decl(tree_node*) ???:0 0xbf95b7 mark_used(tree_node*, int) ???:0 0xb2a403 build_op_call(tree_node*, vec<tree_node*, va_gc, vl_embed>**, int) ???:0 0xd98c6e finish_call_expr(tree_node*, vec<tree_node*, va_gc, vl_embed>**, bool, bool, int) ???:0 0xd166e3 c_parse_file() ???:0 0xe7e469 c_common_parse_file() ???:0 Please submit a full bug report, with preprocessed source (by using -freport-bug). Please include the complete backtrace with any bug report. See <https://gcc.gnu.org/bugs/> for instructions. Godbolt: https://godbolt.org/z/73s69KMd9