| Issue |
178879
|
| Summary |
[Clang][C++20] CTAD on aggregates fails with designated initializers in function templates
|
| Labels |
clang
|
| Assignees |
|
| Reporter |
Attacker23
|
### The following code is rejected by Clang but accepted by GCC, EDG, and MSVC.
https://godbolt.org/z/We8WMz7vo
```cpp
template<typename T>
struct A { T i, j; };
template<typename T>
void foo ()
{
A a = { .i = 1, .j = 3 };
}
int main ()
{
foo<int>();
}
```
### Output:
```
<source>:7:5: error: no viable constructor or deduction guide for deduction of template arguments of 'A'
7 | A a = { .i = 1, .j = 3 };
| ^
<source>:12:3: note: in instantiation of function template specialization 'foo<int>' requested here
12 | foo<int>();
| ^
<source>:2:8: note: candidate template ignored: couldn't infer template argument 'T'
2 | struct A { T i, j; };
| ^
<source>:2:8: note: implicit deduction guide declared as 'template <typename T> A(int, int) -> A<T>'
<source>:2:8: note: candidate function template not viable: requires 1 argument, but 2 were provided
2 | struct A { T i, j; };
| ^
<source>:2:8: note: implicit deduction guide declared as 'template <typename T> A(A<T>) -> A<T>'
<source>:2:8: note: candidate function template not viable: requires 0 arguments, but 2 were provided
<source>:2:8: note: implicit deduction guide declared as 'template <typename T> A() -> A<T>'
1 error generated.
Compiler returned: 1
```
### The following code is accepted by all compilers; Clang has accepted it since version 17.0.1 (as a result of the fix for issue #83368).
https://godbolt.org/z/qEja4afzo
```cpp
template<typename T>
struct A { T i, j; };
int main ()
{
A a = { .i = 1, .j = 3 };
}
```
I believe this is a rejects-valid bug.
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