Keep track of the number of expansions to be produced from a type pack

expansion, when it is known due to the substitution of an out
parameter pack. This allows us to properly handle substitution into
pack expansions that involve multiple parameter packs at different
template parameter levels, even when this substitution happens one
level at a time (as with partial specializations of member class
templates and the signatures of member function templates).

Note that the diagnostic we provide when there is an arity mismatch
between an outer parameter pack and an inner parameter pack in this
case isn't as clear as the normal diagnostic for an arity
mismatch. However, this doesn't matter because these cases are very,
very rare and (even then) only typically occur in a SFINAE context.

The other kinds of pack expansions (expression, template, etc.) still
need to support optional tracking of the number of expansions, and we
need the moral equivalent of SubstTemplateTypeParmPackType for
substituted argument packs of template template and non-type template
parameters.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@123448 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 4 insertions, 0 deletions

diff --git a/lib/AST/TemplateBase.cpp b/lib/AST/TemplateBase.cpp
index 42a936c500..f7c4ac832f 100644
--- a/lib/AST/TemplateBase.cpp
+++ b/lib/AST/TemplateBase.cpp
@@ -346,6 +346,7 @@ SourceRange TemplateArgumentLoc::getSourceRange() const {
 
 TemplateArgumentLoc 
 TemplateArgumentLoc::getPackExpansionPattern(SourceLocation &Ellipsis,
+                                       llvm::Optional<unsigned> &NumExpansions,
                                              ASTContext &Context) const {
   assert(Argument.isPackExpansion());
   
@@ -363,6 +364,7 @@ TemplateArgumentLoc::getPackExpansionPattern(SourceLocation &Ellipsis,
     Ellipsis = Expansion.getEllipsisLoc();
     
     TypeLoc Pattern = Expansion.getPatternLoc();
+    NumExpansions = Expansion.getTypePtr()->getNumExpansions();
     
     // FIXME: This is horrible. We know where the source location data is for
     // the pattern, and we have the pattern's type, but we are forced to copy
@@ -382,10 +384,12 @@ TemplateArgumentLoc::getPackExpansionPattern(SourceLocation &Ellipsis,
       = cast<PackExpansionExpr>(Argument.getAsExpr());
     Expr *Pattern = Expansion->getPattern();
     Ellipsis = Expansion->getEllipsisLoc();
+    // FIXME: Variadic templates num expansions
     return TemplateArgumentLoc(Pattern, Pattern);
   }
 
   case TemplateArgument::TemplateExpansion:
+    // FIXME: Variadic templates num expansions
     Ellipsis = getTemplateEllipsisLoc();
     return TemplateArgumentLoc(Argument.getPackExpansionPattern(),
                                getTemplateQualifierRange(),