1 files changed, 12 insertions, 1 deletions
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 5f4071924d3f..ea4b93ee6a5a 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -350,6 +350,17 @@ bool Sema::DiagnoseUseOfDecl(NamedDecl *D, ArrayRef<SourceLocation> Locs,
     }
   }
 
+  if (isa<ParmVarDecl>(D) && isa<RequiresExprBodyDecl>(D->getDeclContext()) &&
+      !isUnevaluatedContext()) {
+    // C++ [expr.prim.req.nested] p3
+    //   A local parameter shall only appear as an unevaluated operand
+    //   (Clause 8) within the constraint-expression.
+    Diag(Loc, diag::err_requires_expr_parameter_referenced_in_evaluated_context)
+        << D;
+    Diag(D->getLocation(), diag::note_entity_declared_at) << D;
+    return true;
+  }
+
   return false;
 }
 
@@ -1904,7 +1915,7 @@ Sema::BuildDeclRefExpr(ValueDecl *D, QualType Ty, ExprValueKind VK,
   bool RefersToCapturedVariable =
       isa<VarDecl>(D) &&
       NeedToCaptureVariable(cast<VarDecl>(D), NameInfo.getLoc());
-
+  
   DeclRefExpr *E = DeclRefExpr::Create(
       Context, NNS, TemplateKWLoc, D, RefersToCapturedVariable, NameInfo, Ty,
       VK, FoundD, TemplateArgs, getNonOdrUseReasonInCurrentContext(D));