================
@@ -2744,31 +2744,155 @@ bool hasDeclaredDeductionGuides(DeclarationName Name,
DeclContext *DC) {
return false;
}
+unsigned getTemplateDepth(NamedDecl *TemplateParam) {
+ if (auto *TTP = dyn_cast<TemplateTypeParmDecl>(TemplateParam))
+ return TTP->getDepth();
+ if (auto *TTP = dyn_cast<TemplateTemplateParmDecl>(TemplateParam))
+ return TTP->getDepth();
+ if (auto *NTTP = dyn_cast<NonTypeTemplateParmDecl>(TemplateParam))
+ return NTTP->getDepth();
+ llvm_unreachable("Unhandled template parameter types");
+}
+
NamedDecl *transformTemplateParameter(Sema &SemaRef, DeclContext *DC,
NamedDecl *TemplateParam,
MultiLevelTemplateArgumentList &Args,
- unsigned NewIndex) {
+ unsigned NewIndex, unsigned NewDepth) {
if (auto *TTP = dyn_cast<TemplateTypeParmDecl>(TemplateParam))
- return transformTemplateTypeParam(SemaRef, DC, TTP, Args, TTP->getDepth(),
+ return transformTemplateTypeParam(SemaRef, DC, TTP, Args, NewDepth,
NewIndex);
if (auto *TTP = dyn_cast<TemplateTemplateParmDecl>(TemplateParam))
return transformTemplateParam(SemaRef, DC, TTP, Args, NewIndex,
- TTP->getDepth());
+ NewDepth);
if (auto *NTTP = dyn_cast<NonTypeTemplateParmDecl>(TemplateParam))
return transformTemplateParam(SemaRef, DC, NTTP, Args, NewIndex,
- NTTP->getDepth());
+ NewDepth);
llvm_unreachable("Unhandled template parameter types");
}
-Expr *transformRequireClause(Sema &SemaRef, FunctionTemplateDecl *FTD,
- llvm::ArrayRef<TemplateArgument> TransformedArgs)
{
- Expr *RC = FTD->getTemplateParameters()->getRequiresClause();
+// Transform the require-clause of F if any.
+// The return result is expected to be the require-clause for the synthesized
+// alias deduction guide.
+Expr *transformRequireClause(
+ Sema &SemaRef, FunctionTemplateDecl *F,
+ TypeAliasTemplateDecl *AliasTemplate,
+ ArrayRef<DeducedTemplateArgument> DeduceResults) {
+ Expr *RC = F->getTemplateParameters()->getRequiresClause();
if (!RC)
return nullptr;
+
+ auto &Context = SemaRef.Context;
+ LocalInstantiationScope Scope(SemaRef);
+
+ // In the clang AST, constraint nodes are not instantiated at all unless they
+ // are being evaluated. This means that occurrences of template parameters
+ // in the require-clause expr have subtle differences compared to occurrences
+ // in other places, such as function parameters. When transforming the
+ // require-clause, we must respect these differences, particularly regarding
+ // the 'depth' information:
+ // 1) In the transformed require-clause, occurrences of template parameters
+ // must use the "uninstantiated" depth;
+ // 2) When substituting on the require-clause expr of the underlying
+ // deduction guide, we must use the entire set of template argument lists.
+ //
+ // It's important to note that we're performing this transformation on an
+ // *instantiated* AliasTemplate.
+
+ // For 1), if the alias template is nested within a class template, we
+ // calcualte the 'uninstantiated' depth by adding the substitution level
back.
+ unsigned AdjustDepth = 0;
+ if (auto *PrimaryTemplate =
AliasTemplate->getInstantiatedFromMemberTemplate())
----------------
hokein wrote:
I've noticed that there are several places
(e.g.,[1](https://github.com/llvm/llvm-project/blob/main/clang/lib/Sema/SemaTemplate.cpp#L2374),
[2](https://github.com/llvm/llvm-project/blob/main/clang/lib/AST/DeclCXX.cpp#L1943),
[3](https://github.com/llvm/llvm-project/blob/main/clang/lib/AST/Decl.cpp#L4149))
where we use a while-loop to retrieve the primary template. However, I'm not
entirely clear on the rationale behind it. It appears that using
`getInstantiatedFromMemberTemplate()` consistently provides the correct result
for all cases I came up with. Interestingly, removing the while-loop from all
occurrences [1], [2], [3] doesn't trigger any test failures on `check-clang`.
https://github.com/llvm/llvm-project/pull/90961
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