================
@@ -10827,8 +10865,16 @@ DeclResult Sema::ActOnExplicitInstantiation(Scope *S,
return true;
}
- // FIXME: Create an ExplicitInstantiation node?
- return (Decl*) nullptr;
+ const ASTTemplateArgumentListInfo *ArgsAsWritten = nullptr;
+ if (auto *VTSD = dyn_cast<VarTemplateSpecializationDecl>(Prev))
+ ArgsAsWritten = VTSD->getTemplateArgsAsWritten();
+ addExplicitInstantiationDecl(Context, CurContext, D.getCXXScopeSpec(),
Prev,
+ ExternLoc, TemplateLoc, SourceLocation(),
+ ArgsAsWritten, D.getIdentifierLoc(), T, TSK);
+ // Don't return the EID to the Parser — doing so would trigger
+ // unrelated semantic actions (e.g. access checks via
+ // FinalizeDeclaration).
+ return (Decl *)nullptr;
----------------
16bit-ykiko wrote:
I tried returning EID from `ActOnExplicitInstantiation`, but it caused 13 test
failures. Here are the CI results:
https://github.com/llvm/llvm-project/actions/runs/24298212726/artifacts/6390095043
The failures are all access control errors on private members, e.g. explicit
instantiation of private member function templates like `template void
A::f<int>();`.
The root cause is in `PopParsingDeclaration` (`SemaDeclAttr.cpp`): the Parser
uses a delayed diagnostic pool to accumulate access checks during parsing. When
`ActOnExplicitInstantiation` looks up `A::f`, an access check is recorded in
the pool because `f` is private. At the end of parsing,
`PopParsingDeclaration(State, decl)` checks whether `decl` is null — if null,
all delayed diagnostics are silently discarded; if non-null, they are emitted.
Returning EID (non-null) causes the delayed access checks to fire, even though
explicit instantiation of private members is perfectly legal (it happens at
namespace scope, outside the access context).
So returning `nullptr` is the correct behavior here — it tells the Parser that
there's no "new" declaration to validate.
https://github.com/llvm/llvm-project/pull/191658
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