1 files changed, 8 insertions, 1 deletions
diff --git a/clang/lib/Sema/SemaConcept.cpp b/clang/lib/Sema/SemaConcept.cpp
index 11d2d5c..8946f1b 100644
--- a/clang/lib/Sema/SemaConcept.cpp
+++ b/clang/lib/Sema/SemaConcept.cpp
@@ -280,6 +280,11 @@ public:
     if (T->getDepth() >= TemplateArgs.getNumLevels())
       return true;
 
+    // There might not be a corresponding template argument before substituting
+    // into the parameter mapping, e.g. a sizeof... expression.
+    if (!TemplateArgs.hasTemplateArgument(T->getDepth(), T->getIndex()))
+      return true;
+
     TemplateArgument Arg = TemplateArgs(T->getDepth(), T->getIndex());
 
     if (T->isParameterPack() && SemaRef.ArgPackSubstIndex) {
@@ -1049,6 +1054,7 @@ ExprResult ConstraintSatisfactionChecker::Evaluate(
   case NormalizedConstraint::ConstraintKind::Compound:
     return Evaluate(static_cast<const CompoundConstraint &>(Constraint), MLTAL);
   }
+  llvm_unreachable("Unknown ConstraintKind enum");
 }
 
 static bool CheckConstraintSatisfaction(
@@ -2141,6 +2147,7 @@ bool SubstituteParameterMappings::substitute(NormalizedConstraint &N) {
     return substitute(Compound.getRHS());
   }
   }
+  llvm_unreachable("Unknown ConstraintKind enum");
 }
 
 } // namespace
@@ -2561,7 +2568,6 @@ FormulaType SubsumptionChecker::Normalize(const NormalizedConstraint &NC) {
   };
 
   switch (NC.getKind()) {
-
   case NormalizedConstraint::ConstraintKind::Atomic:
     return {{find(&static_cast<const AtomicConstraint &>(NC))}};
 
@@ -2601,6 +2607,7 @@ FormulaType SubsumptionChecker::Normalize(const NormalizedConstraint &NC) {
     return Res;
   }
   }
+  llvm_unreachable("Unknown ConstraintKind enum");
 }
 
 void SubsumptionChecker::AddUniqueClauseToFormula(Formula &F, Clause C) {