update code according to suggested changes

Author: Benjamin Tong

src/compiler/checker.ts

@@ -21455,7 +21455,6 @@ namespace ts {
          * with no call or construct signatures.
          */
         function isObjectTypeWithInferableIndex(type: Type): boolean {
-            const objectFlags = getObjectFlags(type);
             return type.flags & TypeFlags.Intersection
                 ? every((type as IntersectionType).types, isObjectTypeWithInferableIndex)
                 : !!(
@@ -21464,8 +21463,7 @@ namespace ts {
                     && !(type.symbol.flags & SymbolFlags.Class)
                     && !typeHasCallOrConstructSignatures(type)
                 ) || !!(
-                    objectFlags
-                    && objectFlags & ObjectFlags.ObjectRestType
+                    getObjectFlags(type) & ObjectFlags.ObjectRestType
                 ) || !!(getObjectFlags(type) & ObjectFlags.ReverseMapped && isObjectTypeWithInferableIndex((type as ReverseMappedType).source));
         }