Function getSpreadType

test/fixtures/snapshot/typescript.js:62907–62990

* Since the source of spread types are object literals, which are not binary, * this function should be called in a left folding style, with left = previous result of getSpreadType * and right = the new element to be spread.

(left, right, symbol, objectFlags, readonly)

         * and right = the new element to be spread.
         */
        function getSpreadType(left, right, symbol, objectFlags, readonly) {
            if (left.flags & 1 /* TypeFlags.Any */ || right.flags & 1 /* TypeFlags.Any */) {
                return anyType;
            }
            if (left.flags & 2 /* TypeFlags.Unknown */ || right.flags & 2 /* TypeFlags.Unknown */) {
                return unknownType;
            }
            if (left.flags & 131072 /* TypeFlags.Never */) {
                return right;
            }
            if (right.flags & 131072 /* TypeFlags.Never */) {
                return left;
            }
            left = tryMergeUnionOfObjectTypeAndEmptyObject(left, readonly);
            if (left.flags & 1048576 /* TypeFlags.Union */) {
                return checkCrossProductUnion([left, right])
                    ? mapType(left, function (t) { return getSpreadType(t, right, symbol, objectFlags, readonly); })
                    : errorType;
            }
            right = tryMergeUnionOfObjectTypeAndEmptyObject(right, readonly);
            if (right.flags & 1048576 /* TypeFlags.Union */) {
                return checkCrossProductUnion([left, right])
                    ? mapType(right, function (t) { return getSpreadType(left, t, symbol, objectFlags, readonly); })
                    : errorType;
            }
            if (right.flags & (528 /* TypeFlags.BooleanLike */ | 296 /* TypeFlags.NumberLike */ | 2112 /* TypeFlags.BigIntLike */ | 402653316 /* TypeFlags.StringLike */ | 1056 /* TypeFlags.EnumLike */ | 67108864 /* TypeFlags.NonPrimitive */ | 4194304 /* TypeFlags.Index */)) {
                return left;
            }
            if (isGenericObjectType(left) || isGenericObjectType(right)) {
                if (isEmptyObjectType(left)) {
                    return right;
                }
                // When the left type is an intersection, we may need to merge the last constituent of the
                // intersection with the right type. For example when the left type is 'T & { a: string }'
                // and the right type is '{ b: string }' we produce 'T & { a: string, b: string }'.
                if (left.flags & 2097152 /* TypeFlags.Intersection */) {
                    var types = left.types;
                    var lastLeft = types[types.length - 1];
                    if (isNonGenericObjectType(lastLeft) && isNonGenericObjectType(right)) {
                        return getIntersectionType(ts.concatenate(types.slice(0, types.length - 1), [getSpreadType(lastLeft, right, symbol, objectFlags, readonly)]));
                    }
                }
                return getIntersectionType([left, right]);
            }
            var members = ts.createSymbolTable();
            var skippedPrivateMembers = new ts.Set();
            var indexInfos = left === emptyObjectType ? getIndexInfosOfType(right) : getUnionIndexInfos([left, right]);
            for (var _i = 0, _a = getPropertiesOfType(right); _i < _a.length; _i++) {
                var rightProp = _a[_i];
                if (ts.getDeclarationModifierFlagsFromSymbol(rightProp) & (8 /* ModifierFlags.Private */ | 16 /* ModifierFlags.Protected */)) {
                    skippedPrivateMembers.add(rightProp.escapedName);
                }
                else if (isSpreadableProperty(rightProp)) {
                    members.set(rightProp.escapedName, getSpreadSymbol(rightProp, readonly));
                }
            }
            for (var _b = 0, _c = getPropertiesOfType(left); _b < _c.length; _b++) {
                var leftProp = _c[_b];