Function getOptionalType

test/fixtures/snapshot/typescript.js:67634–67638

(type, isProperty)

                        getUnionType([type, undefinedType, nullType]);
        }
        function getOptionalType(type, isProperty) {
            if (isProperty === void 0) { isProperty = false; }
            ts.Debug.assert(strictNullChecks);
            return type.flags & 32768 /* TypeFlags.Undefined */ ? type : getUnionType([type, isProperty ? missingType : undefinedType]);
        }
        function getGlobalNonNullableTypeInstantiation(type) {
            // First reduce away any constituents that are assignable to 'undefined' or 'null'. This not only eliminates
            // 'undefined' and 'null', but also higher-order types such as a type parameter 'U extends undefined | null'