pack tests, remove dead code

Author: cor3ntin

clang/include/clang/Sema/Sema.h

@@ -12779,7 +12779,7 @@ class Sema final : public SemaBase {
   /// Mark which template parameters are named in a given expression.
   ///
   /// Unlike MarkUsedTemplateParameters, this excludes parameter that
-  /// are used but not directly named by an expression - ie it excludes
+  /// are used but not directly named by an expression - i.e. it excludes
   /// any template parameter that denotes the type of a referenced NTTP.
   ///
   /// \param Used a bit vector whose elements will be set to \c true

clang/lib/Sema/SemaConcept.cpp

@@ -1937,10 +1937,6 @@ void SubstituteParameterMappings::buildParameterMapping(
         static_cast<FoldExpandedConstraint &>(N).getPattern(),
         /*OnlyDeduced=*/false,
         /*Depth=*/0, OccurringIndices);
-
-    SemaRef.MarkUsedTemplateParametersForSubsumptionParameterMapping(
-        static_cast<FoldExpandedConstraint &>(N).getPattern(),
-        /*Depth=*/0, OccurringIndicesForSubsumption);
   }
   TemplateArgumentLoc *TempArgs =
       new (SemaRef.Context) TemplateArgumentLoc[OccurringIndices.count()];

clang/test/SemaTemplate/instantiate-template-argument.cpp

@@ -57,6 +57,24 @@ static_assert(foo<int, 'a'>() == 2);
 
 }
 
+namespace packs {
+
+template<auto T, decltype(T)... U>
+concept C1 = (sizeof(U) && ...) >= 4;
+
+template<typename Y, char... V>
+concept C2 = (C1<Y{}, V> && ...);
+
+template<char... W>
+constexpr int foo() requires (C2<int, W> && ...) { return 1; }
+
+template<char... X>
+constexpr int foo() requires (C1<1, X> && ...) && true { return 2; }
+
+static_assert(foo<'a'>() == 2);
+
+}
+
 namespace case2 {
 template<auto T> concept C1 = sizeof(decltype(T)) >= 0;
 template<typename Y> concept C2 = C1<Y{}>;