PR32673: Don't wrap parameter packs in SubstTemplateTypeParmPackType nodes when forming implicit deduction guides.
Doing so thwarts template type deduction. Instead, substitute the pack directly
by picking "slice 0" of the resulting expansion.
llvm-svn: 300805
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index f522e76..61b4df4 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -1636,11 +1636,22 @@
transformFunctionTypeParam(ParmVarDecl *OldParam,
MultiLevelTemplateArgumentList &Args) {
TypeSourceInfo *OldDI = OldParam->getTypeSourceInfo();
- TypeSourceInfo *NewDI =
- Args.getNumLevels()
- ? SemaRef.SubstType(OldDI, Args, OldParam->getLocation(),
- OldParam->getDeclName())
- : OldDI;
+ TypeSourceInfo *NewDI;
+ if (!Args.getNumLevels())
+ NewDI = OldDI;
+ else if (auto PackTL = OldDI->getTypeLoc().getAs<PackExpansionTypeLoc>()) {
+ // Expand out the one and only element in each inner pack.
+ Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(SemaRef, 0);
+ NewDI =
+ SemaRef.SubstType(PackTL.getPatternLoc(), Args,
+ OldParam->getLocation(), OldParam->getDeclName());
+ if (!NewDI) return nullptr;
+ NewDI =
+ SemaRef.CheckPackExpansion(NewDI, PackTL.getEllipsisLoc(),
+ PackTL.getTypePtr()->getNumExpansions());
+ } else
+ NewDI = SemaRef.SubstType(OldDI, Args, OldParam->getLocation(),
+ OldParam->getDeclName());
if (!NewDI)
return nullptr;