https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97214
Bug ID: 97214 Summary: ICE in lookup_template_class_1, at cp/pt.c:9896 Product: gcc Version: 10.2.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: sfranzen85 at hotmail dot com Target Milestone: --- The following snippet reproduces an error I encountered with lambdas: struct Foo { // void operator()(int) {} template<typename T> void operator()(T, T) { auto bar = [this](auto&& v){ operator()(v); }; } }; int main () { Foo{}(0,1); return 0; } Full error: ../src/main.cpp: In instantiation of ‘void Foo::operator()(T, T) [with T = int]’: ../src/main.cpp:13:14: required from here ../src/main.cpp:7:38: internal compiler error: in lookup_template_class_1, at cp/pt.c:9896 7 | auto bar = [this](auto&& v){ operator()(v); }; | ^~~~~~~~~~ Further observations: * The error appears regardless of available operator()() overloads; * It only appears if the function call is unqualified, e.g. (*this)(v) is fine if the overload exists. A possibly related error is given using a version of Foo without a function template: struct Foo { void operator()(int) {} void operator()(int a, int) { auto bar = [this](auto&& v){ operator()(v); }; bar(a); } }; ../src/main.cpp: In instantiation of ‘Foo::operator()(int, int)::<lambda(auto:1&&)> [with auto:1 = int&]’: ../src/main.cpp:8:14: required from here ../src/main.cpp:7:48: error: use of ‘Foo::operator()(int, int)::<lambda(auto:1&&)> [with auto:1 = int&]’ before deduction of ‘auto’ 7 | auto bar = [this](auto&& v){ operator()(v); }; | ~~~~~~~~~~^~~ This error similarly only appears with the unqualified call, and also disappears if the lambda has '-> void'.