[Concepts] Add check for dependent RC when checking function constraints

Do not attempt to check a dependent requires clause in a function constraint
(may be triggered by, for example, DiagnoseUseOfDecl).
diff --git a/clang/lib/Sema/SemaConcept.cpp b/clang/lib/Sema/SemaConcept.cpp
index e5c0fa2..8fdc602 100755
--- a/clang/lib/Sema/SemaConcept.cpp
+++ b/clang/lib/Sema/SemaConcept.cpp
@@ -325,9 +325,10 @@
                                     ConstraintSatisfaction &Satisfaction,
                                     SourceLocation UsageLoc) {
   const Expr *RC = FD->getTrailingRequiresClause();
-  assert(!RC->isInstantiationDependent() &&
-         "CheckFunctionConstraints can only be used with functions with "
-         "non-dependent constraints");
+  if (RC->isInstantiationDependent()) {
+    Satisfaction.IsSatisfied = true;
+    return false;
+  }
   // We substitute with empty arguments in order to rebuild the atomic
   // constraint in a constant-evaluated context.
   // FIXME: Should this be a dedicated TreeTransform?