Limit check to only fresh object literals on the source side

Author: ahejlsberg

src/compiler/checker.ts

@@ -20693,7 +20693,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                     isNonGenericObjectType(target) && !isArrayOrTupleType(target) && source.flags & TypeFlags.Intersection && getApparentType(source).flags & TypeFlags.StructuredType && !some((source as IntersectionType).types, t => !!(getObjectFlags(t) & ObjectFlags.NonInferrableType)))) {
                     inPropertyCheck = true;
                     result &= propertiesRelatedTo(source, target, reportErrors, /*excludedProperties*/ undefined, IntersectionState.None);
-                    if (result) {
+                    if (result && isObjectLiteralType(source) && getObjectFlags(source) & ObjectFlags.FreshLiteral) {
                         result &= indexSignaturesRelatedTo(source, target, /*sourceIsPrimitive*/ false, reportErrors, IntersectionState.None);
                     }
                     inPropertyCheck = false;