Function appendTypeMapping

test/fixtures/snapshot/typescript.js:63334–63336

(mapper, source, target)

            return !mapper ? makeUnaryTypeMapper(source, target) : makeCompositeTypeMapper(4 /* TypeMapKind.Merged */, makeUnaryTypeMapper(source, target), mapper);
        }
        function appendTypeMapping(mapper, source, target) {
            return !mapper ? makeUnaryTypeMapper(source, target) : makeCompositeTypeMapper(4 /* TypeMapKind.Merged */, mapper, makeUnaryTypeMapper(source, target));
        }
        function getRestrictiveTypeParameter(tp) {
            return tp.constraint === unknownType ? tp : tp.restrictiveInstantiation || (tp.restrictiveInstantiation = createTypeParameter(tp.symbol),
                tp.restrictiveInstantiation.constraint = unknownType,