1 files changed, 11 insertions, 4 deletions
diff --git a/lib/Sema/SemaTemplateInstantiateDecl.cpp b/lib/Sema/SemaTemplateInstantiateDecl.cpp
index 818548cb62..d1ad304e62 100644
--- a/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -3515,14 +3515,21 @@ TemplateDeclInstantiator::SubstTemplateParams(TemplateParameterList *L) {
   if (Invalid)
     return nullptr;
 
-  // Note: we substitute into associated constraints later
-  Expr *const UninstantiatedRequiresClause = L->getRequiresClause();
+  // FIXME: Concepts: Substitution into requires clause should only happen when
+  // checking satisfaction.
+  Expr *InstRequiresClause = nullptr;
+  if (Expr *E = L->getRequiresClause()) {
+    ExprResult Res = SemaRef.SubstExpr(E, TemplateArgs);
+    if (Res.isInvalid() || !Res.isUsable()) {
+      return nullptr;
+    }
+    InstRequiresClause = Res.get();
+  }
 
   TemplateParameterList *InstL
     = TemplateParameterList::Create(SemaRef.Context, L->getTemplateLoc(),
                                     L->getLAngleLoc(), Params,
-                                    L->getRAngleLoc(),
-                                    UninstantiatedRequiresClause);
+                                    L->getRAngleLoc(), InstRequiresClause);
   return InstL;
 }