https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81157
Bug ID: 81157
Summary: If constexpr does not support Short-circuit evaluation
Product: gcc
Version: 7.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: kmp53 at sina dot com
Target Milestone: ---
template <typename T,typename U> concept bool Same=std::is_same_v<T,U>;
template<typename T> concept bool IsContainer=requires(T t){
t.cnt();
typename T::innerType;
};
struct Ct {
void cnt(){;}
using innerType=int;
};
template<class V>
requires IsContainer<V>&&Same<typename V::innerType,int>||Same<V,int> void
fn(const V &a) {
void fn(const V &a) {
if constexpr(IsContainer<V>&&Same<typename V::innerType,int>) ;//①
//if constexpr(IsContainer<V>)//②
//if constexpr(Same<typename V::innerType,int>) ;
else if (Same<V,int>) ;
}
int main(int argc,char*argv[]){
fn(1);//ill-formed
fn(Ct());//OK
}
Concept supports short expressions, while if constexpr does not.
When I write ①, there is an error
'int' is not a class, struct, or union type
If it is written ②, there will be no problem. Is it a bug or a defect?
