[CSApply] Mark dynamic member lookup subscript expr and its argument as implicit

These expressions are created to model an implicit call to dynamic
member lookup endpoint, which means both of them have to be implicit.

Author: xedin

lib/Sema/CSApply.cpp

@@ -2863,18 +2863,16 @@ namespace {
       auto tupleTy =
           TupleType::get(TupleTypeElt(paramTy, ctx.Id_dynamicMember), ctx);
 
-      auto loc = nameLoc;
-      Expr *index = TupleExpr::create(ctx, loc, argExpr, ctx.Id_dynamicMember,
-                                      loc, loc, /*hasTrailingClosure*/ false,
-                                      /*implicit*/ true);
+      Expr *index =
+          TupleExpr::createImplicit(ctx, argExpr, ctx.Id_dynamicMember);
       index->setType(tupleTy);
       cs.cacheType(index);
 
       // Build and return a subscript that uses this string as the index.
       return buildSubscript(
           base, index, ctx.Id_dynamicMember,
           /*trailingClosure*/ false, cs.getConstraintLocator(expr),
-          /*isImplicit*/ false, AccessSemantics::Ordinary, overload);
+          /*isImplicit*/ true, AccessSemantics::Ordinary, overload);
     }
 
     Type getTypeOfDynamicMemberIndex(const SelectedOverload &overload) {