[Bug c++/90426] [P0732] Error constructing non-type template parameter from a prvalue
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90426 --- Comment #6 from Marek Polacek --- I posted a patch to improve diagnostics for this particular case: https://gcc.gnu.org/ml/gcc-patches/2019-05/msg00529.html
[Bug c++/90426] [P0732] Error constructing non-type template parameter from a prvalue
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90426
--- Comment #5 from Mateusz Pusz ---
(In reply to Mateusz Pusz from comment #3)
> (In reply to Marek Polacek from comment #1)
> > This compiles if I use {} instead of ():
> >
> > struct gram : unit {};
>
> (In reply to Marek Polacek from comment #2)
> > I think this is invalid. [temp.arg]p2:
> > "In a template-argument, an ambiguity between a type-id and an expression is
> > resolved to a type-id, regardless of the form of the corresponding
> > template-parameter."
> >
> > template
> > struct S { };
> >
> > struct R { };
> >
> > void
> > g (void)
> > {
> > S s; // template argument treated as function type
> > S s2;
> > S s3; // template argument treated as function type
> > S s4;
> > }
>
> Please note that all of the following compiles fine and is not treated as a
> function type (most vexing parse)
>
> constexpr auto r1(ratio(std::milli()));
> constexpr auto r2(ratio(std::milli()));
> constexpr ratio r3(std::milli());
My bad, that actually is a most vexing parse issue. Sorry!
[Bug c++/90426] [P0732] Error constructing non-type template parameter from a prvalue
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90426
--- Comment #4 from Mateusz Pusz ---
(In reply to Marek Polacek from comment #1)
> This compiles if I use {} instead of ():
>
> struct gram : unit {};
I know that it compiles fine in the following cases:
struct gram : unit {};
struct gram : unit {}; // not treated as a function type
struct gram : unit {};
So the only one lacking is:
struct gram : unit {};
[Bug c++/90426] [P0732] Error constructing non-type template parameter from a prvalue
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90426
--- Comment #3 from Mateusz Pusz ---
(In reply to Marek Polacek from comment #1)
> This compiles if I use {} instead of ():
>
> struct gram : unit {};
(In reply to Marek Polacek from comment #2)
> I think this is invalid. [temp.arg]p2:
> "In a template-argument, an ambiguity between a type-id and an expression is
> resolved to a type-id, regardless of the form of the corresponding
> template-parameter."
>
> template
> struct S { };
>
> struct R { };
>
> void
> g (void)
> {
> S s; // template argument treated as function type
> S s2;
> S s3; // template argument treated as function type
> S s4;
> }
Please note that all of the following compiles fine and is not treated as a
function type (most vexing parse)
constexpr auto r1(ratio(std::milli()));
constexpr auto r2(ratio(std::milli()));
constexpr ratio r3(std::milli());
[Bug c++/90426] [P0732] Error constructing non-type template parameter from a prvalue
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90426
Marek Polacek changed:
What|Removed |Added
Status|UNCONFIRMED |RESOLVED
Resolution|--- |INVALID
--- Comment #2 from Marek Polacek ---
I think this is invalid. [temp.arg]p2:
"In a template-argument, an ambiguity between a type-id and an expression is
resolved to a type-id, regardless of the form of the corresponding
template-parameter."
template
struct S { };
struct R { };
void
g (void)
{
S s; // template argument treated as function type
S s2;
S s3; // template argument treated as function type
S s4;
}
[Bug c++/90426] [P0732] Error constructing non-type template parameter from a prvalue
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90426
Marek Polacek changed:
What|Removed |Added
CC||mpolacek at gcc dot gnu.org
--- Comment #1 from Marek Polacek ---
This compiles if I use {} instead of ():
struct gram : unit {};
