================
@@ -9180,6 +9180,12 @@ bool Sema::hasAcceptableDefinition(NamedDecl *D,
NamedDecl **Suggested,
if (!getLangOpts().Modules && !getLangOpts().ModulesLocalVisibility)
return true;
+ // The external source may have additional definitions of this entity that
are
+ // visible, so complete the redeclaration chain now.
+ if (auto *Source = Context.getExternalSource()) {
+ Source->CompleteRedeclChain(D);
+ }
----------------
mpark wrote:
So the issue has to do with `ClassTemplateDecl`,
`ClassTemplateSpecializationDecl`, and `CXXRecordDecl`.
I'll describe my observations in the problematic invocation of
`hasAcceptableDefinition`.
I believe there are 4 relevant pieces here:
1. `ClassTemplateSpecializationDecl` for `BS<Empty<int>>`
2. `CXXRecordDecl` for `BS<Empty<int>>` (base portion of (1))
3. `ClassTemplateDecl` for `BS<T>`
4. `CXXRecordDecl` for `BS<T>`
`NamedDecl* D` coming into `hasAcceptableDefinition` points to a `NamedDecl`
base portion of `ClassTemplateSpecializationDecl` for `BS<Empty<int>>` [1].
`auto* RD = dyn_cast<CXXRecordDecl>(D)` is the `CXXRecordDecl` portion of
`BS<Empty<int>>` [2]. `auto *Pattern = RD->getTemplateInstantiationPattern()`
is an instance of `CXXRecordDecl` for `BS<T>` [4].
Whatever the reason, at this point the *definition* of [4] has not been loaded
yet. I would've expected that the call to `RD->getDefinition()` (which has a
dummy invocation to `getMostRecentDecl()` under the hood) should load the
definition, but this does not happen for some reason.
However, calling `getMostRecentDecl()` on any of [1], [2] or [3] have the
desired effect of loading the definition of [4]... e.g.
`RD->getMostRecentDecl()` calls it on [2] which loads the definition of [4],
and `Pattern->getDescribedClassTemplate()->getMostRecentDecl()` calls it on [3]
which also gives us the definition of [4] we're looking for...
The current solution here effectively is to call `getMostRecentDecl` on [2]
such that it loads the redecl chain which somehow includes the definition of
[4]... but maybe the real solution is to figure out why the `getMostRecentDecl`
call on [4] itself doesn't load the corresponding definition?
https://github.com/llvm/llvm-project/pull/129982
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