| Issue |
114069
|
| Summary |
[clang] Class fields with placeholder names cause incorrect instantiation of in-class initializers
|
| Labels |
clang
|
| Assignees |
|
| Reporter |
groundswellaudio
|
MRE :
https://godbolt.org/z/Mjdnz8G31
```cpp
#include <cassert>
template <class T>
struct A {
T _ = 5;
T _ = 4;
};
int main() {
A<int> a;
auto [x, y] = a;
assert( y == 4 );
}
```
`assert( y == 4 )` fails because Clang finds the in-class init pattern like this (in Sema::BuildCXXDefaultInitExpr) :
```cpp
CXXRecordDecl *ClassPattern = ParentRD->getTemplateInstantiationPattern();
DeclContext::lookup_result Lookup = ClassPattern->lookup(Field->getDeclName());
FieldDecl *Pattern = nullptr;
for (auto *L : Lookup) {
if ((Pattern = dyn_cast<FieldDecl>(L)))
break;
}
```
Obviously this cannot works with `_`. I think to remedy this imply keeping track of the pattern of an instantiated field with a placeholder name in some auxiliary structure? The entry would only need to be temporary until its consumed by Sema::BuildCXXDefaultInitExpr.
Also I think a warning should be emitted that we're using a C++26 feature before its time?
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