| Issue |
178860
|
| Summary |
Static variable template with deduced type within a class template is rejected
|
| Labels |
clang:frontend,
confirmed,
diverges-from:gcc,
diverges-from:msvc,
diverges-from:edg
|
| Assignees |
|
| Reporter |
Endilll
|
Consider the following example:
```cpp
template <typename>
struct A {
template <typename>
static constexpr auto value = 5;
};
decltype(A<void>::value<void>) x{};
```
Clang has been rejecting this since 9 (https://godbolt.org/z/8xMYEW51a), but other compilers accept (https://godbolt.org/z/Wcnz4K8f6):
```
<source>:13:37: error: illegal initializer type 'decltype(A<void>::value<void>)' (aka 'const auto')
13 | decltype(A<void>::value<void>) x{};
| ^
```
Consider the following example derived from the first one that adds a type alias:
```cpp
template <typename>
struct A {
template <typename>
static constexpr auto value = 5;
using result_t = decltype(value<void>);
};
decltype(A<void>::value<void>) x{};
```
Clang has been rejecting this since 12 with the same diagnostic as above (https://godbolt.org/z/zqaExM1a8), but other compiler accept (https://godbolt.org/z/zxx1acje6). Since 21 we issue a different diagnostic:
```
<source>:9:19: error: the type of variable template specialization 'value<void>' declared with deduced type 'const auto' depends on itself
9 | decltype(A<void>::value<void>) x{};
| ^
```
Related: #147992, #134526, #45408
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