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* [Bug c++/101435] New: Bad error with missing typename keyword
@ 2021-07-13 10:57 tobi at gcc dot gnu.org
2021-07-13 11:02 ` [Bug c++/101435] " tobi at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: tobi at gcc dot gnu.org @ 2021-07-13 10:57 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101435
Bug ID: 101435
Summary: Bad error with missing typename keyword
Product: gcc
Version: 11.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: tobi at gcc dot gnu.org
Target Milestone: ---
Consider (https://godbolt.org/z/hxnv779Tr):
===================================
template<typename U, int dim>
class X {
public:
U v;
using Scalar = U;
static constexpr auto Dim = dim;
explicit X(U x) : v(x) {}
template<typename T>
X<T, dim> cast()
{
return X<T, dim>(T{v});
}
};
void f(int err) {
auto propertyHelper = [err]<typename M>(M&& fallback) -> M {
using FloatM = X<float, M::Dim>;
FloatM v{0};
return err == 0 ? M{ v.cast<typename M::Scalar>() } : fallback;
};
}
================================
This gives the fairly confusing error messages:
+++++++++++++++++++++++++++++++
<source>: In lambda function:
<source>:23:28: error: expected primary-expression before '{' token
23 | return err == 0 ? M{ v.cast<typename M::Scalar>() } : fallback;
| ^
<source>:23:28: error: expected ':' before '{' token
23 | return err == 0 ? M{ v.cast<typename M::Scalar>() } : fallback;
| ^
| :
<source>:23:28: error: expected primary-expression before '{' token
<source>:23:28: error: expected ';' before '{' token
23 | return err == 0 ? M{ v.cast<typename M::Scalar>() } : fallback;
| ^
| ;
<source>:23:55: error: expected '(' before '>' token
23 | return err == 0 ? M{ v.cast<typename M::Scalar>() } : fallback;
| ^
| (
<source>:23:57: error: expected primary-expression before ')' token
23 | return err == 0 ? M{ v.cast<typename M::Scalar>() } : fallback;
| ^
<source>:23:58: error: expected ';' before '}' token
23 | return err == 0 ? M{ v.cast<typename M::Scalar>() } : fallback;
| ^~
| ;
<source>:23:61: error: expected primary-expression before ':' token
23 | return err == 0 ? M{ v.cast<typename M::Scalar>() } : fallback;
| ^
Compiler returned: 1
+++++++++++++++++++++++++++++++
The actual cause of the error is the missing typename keyword before M (clang
points this out correctly, MSVC of course accepts the code without error
message). This is similar to #63392 but in that case we at least get a hint as
to what the actual problem is.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c++/101435] Bad error with missing typename keyword
2021-07-13 10:57 [Bug c++/101435] New: Bad error with missing typename keyword tobi at gcc dot gnu.org
@ 2021-07-13 11:02 ` tobi at gcc dot gnu.org
2021-07-13 12:10 ` redi at gcc dot gnu.org
2021-07-14 1:56 ` [Bug c++/101435] Bad error with missing template keyword tobi at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: tobi at gcc dot gnu.org @ 2021-07-13 11:02 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101435
--- Comment #1 from Tobias Schlüter <tobi at gcc dot gnu.org> ---
Grrr, I made a mistake in describing the issue with the code: what is missing
is the `template` keyword before `cast`, so it should read
return err == 0 ? M{ v.template cast<typename M::Scalar>() } : fallback;
^^^^^^^^^
Of course GCC gives errors everywhere but there :D
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c++/101435] Bad error with missing typename keyword
2021-07-13 10:57 [Bug c++/101435] New: Bad error with missing typename keyword tobi at gcc dot gnu.org
2021-07-13 11:02 ` [Bug c++/101435] " tobi at gcc dot gnu.org
@ 2021-07-13 12:10 ` redi at gcc dot gnu.org
2021-07-14 1:56 ` [Bug c++/101435] Bad error with missing template keyword tobi at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: redi at gcc dot gnu.org @ 2021-07-13 12:10 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101435
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
Last reconfirmed| |2021-07-13
Keywords| |diagnostic
See Also| |https://gcc.gnu.org/bugzill
| |a/show_bug.cgi?id=16233
--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Right, "typename M" would be invalid, you only need "typename" before a nested
name like M::Scalar, where M is dependent. This is nothing to do with PR 63392.
Confirmed as a diagnostic bug. It would be good to get a fix-it here. Maybe a
dup of PR 16233.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c++/101435] Bad error with missing template keyword
2021-07-13 10:57 [Bug c++/101435] New: Bad error with missing typename keyword tobi at gcc dot gnu.org
2021-07-13 11:02 ` [Bug c++/101435] " tobi at gcc dot gnu.org
2021-07-13 12:10 ` redi at gcc dot gnu.org
@ 2021-07-14 1:56 ` tobi at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: tobi at gcc dot gnu.org @ 2021-07-14 1:56 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101435
--- Comment #3 from Tobias Schlüter <tobi at gcc dot gnu.org> ---
Thank you! I would certainly have found the other bug had I put the right
keyword into the title of the PR myself ...
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2021-07-14 1:56 UTC | newest]
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2021-07-13 10:57 [Bug c++/101435] New: Bad error with missing typename keyword tobi at gcc dot gnu.org
2021-07-13 11:02 ` [Bug c++/101435] " tobi at gcc dot gnu.org
2021-07-13 12:10 ` redi at gcc dot gnu.org
2021-07-14 1:56 ` [Bug c++/101435] Bad error with missing template keyword tobi at gcc dot gnu.org
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