https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104548
Bug ID: 104548
Summary: parser rejects alias template id of lambda in
unevaluated-context and accepts when no alias is used
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: nickhuang99 at hotmail dot com
Target Milestone: ---
I feel this issue is related with PR104537 and PR104358
Parser rejects following code with alias of template id:
https://www.godbolt.org/z/eec3T5ebj
template<typename T>
using FunPtr=decltype(+[](T t)->T{return t+1;});
template<typename T>
auto foo(T t, FunPtr<T> funPtr){
return funPtr(t);
}
void test(){
// parser rejects when using alias
foo<int>(5, [](int t){return t+1;});
}
<source>:14:21: error: invalid user-defined conversion from
'test()::<lambda(int)>' to 'int' [-fpermissive]
14 | foo<int>(5, [](int t){return t+1;});
| ^~~~~~~~~~~~~~~~~~~~~~
And accepts exact same code when NO alias is used:
template<typename T>
auto foo(T t, decltype(+[](T t)->T{return t+1;}) lam){
return lam(t);
}
void test(){
// parser accepts when no alias is used
foo<int>(5, [](int t){return t+1;});
}
