================
@@ -3239,61 +3162,11 @@ bool Sema::SubstTypeConstraint(
TC->getTemplateArgsAsWritten();
if (!EvaluateConstraints) {
- bool ShouldExpandExplicitTemplateArgs =
- TemplArgInfo && ArgumentPackSubstitutionIndex != -1 &&
- llvm::any_of(TemplArgInfo->arguments(), [](auto &Arg) {
- return Arg.getArgument().containsUnexpandedParameterPack();
- });
-
- // We want to transform the packs into Subst* nodes for type constraints
- // inside a pack expansion. For example,
- //
- // template <class... Ts> void foo() {
- // bar([](C<Ts> auto value) {}...);
- // }
- //
- // As we expand Ts in the process of instantiating foo(), and retain
- // the original template depths of Ts until the constraint evaluation, we
- // would otherwise have no chance to expand Ts by the time of evaluating
- // C<auto, Ts>.
- //
- // So we form a Subst* node for Ts along with a proper substitution index
- // here, and substitute the node with a complete MLTAL later in evaluation.
- if (ShouldExpandExplicitTemplateArgs) {
- TemplateArgumentListInfo InstArgs;
- InstArgs.setLAngleLoc(TemplArgInfo->LAngleLoc);
- InstArgs.setRAngleLoc(TemplArgInfo->RAngleLoc);
- if (ExpandPackedTypeConstraints(*this, TemplateArgs)
- .SubstTemplateArguments(TemplArgInfo->arguments(), InstArgs))
- return true;
-
- // The type of the original parameter.
- auto *ConstraintExpr = TC->getImmediatelyDeclaredConstraint();
- QualType ConstrainedType;
-
- if (auto *FE = dyn_cast<CXXFoldExpr>(ConstraintExpr)) {
- assert(FE->getLHS());
- ConstraintExpr = FE->getLHS();
- }
- auto *CSE = cast<ConceptSpecializationExpr>(ConstraintExpr);
- assert(!CSE->getTemplateArguments().empty() &&
- "Empty template arguments?");
- ConstrainedType = CSE->getTemplateArguments()[0].getAsType();
- assert(!ConstrainedType.isNull() &&
- "Failed to extract the original ConstrainedType?");
-
- return AttachTypeConstraint(
- TC->getNestedNameSpecifierLoc(), TC->getConceptNameInfo(),
- TC->getNamedConcept(),
- /*FoundDecl=*/TC->getConceptReference()->getFoundDecl(), &InstArgs,
- Inst, ConstrainedType,
- Inst->isParameterPack()
- ? cast<CXXFoldExpr>(TC->getImmediatelyDeclaredConstraint())
- ->getEllipsisLoc()
- : SourceLocation());
- }
+ auto Index = TC->getArgumentPackSubstitutionIndex();
+ if (Index == -1)
+ Index = SemaRef.ArgumentPackSubstitutionIndex;
----------------
zyn0217 wrote:
> If on a first transform pass this is not expanded and we see
> ArgumentPackSubstitutionIndex != -1, then it becomes expanded.
It doesn't perform actual expansion until the constraint checking, right? So we
just track the value of ArgumentPackSubstitutionIndex and make use of it before
evaluating constraints. I believe this is what we both wanted.
What I'm asking is, is it possible that, we run into this function multiple
times before we actually evaluate the constraint, and each time we end up in
this function with a different ArgumentPackSubstitutionIndex? It's true that we
record the first non -1 ArgumentPackSubstitutionIndex in the first pass, and I
think we should assume that it remains unchanged in the subsequent passes.
https://github.com/llvm/llvm-project/pull/132626
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