readonly modifier throws errors during compilation

[RoxKilly]

Expected behavior:
Valid typescript syntax should not raise errors during compilation.

Actual behavior:
The readonly modifier causes compilation errors. Eg, this line:

readonly change: Observable<MdButtonToggleChange>;

Throws the following errors during compilation:

error TS1005: '=' expected.
error TS1005: ';' expected.
error TS1005: '(' expected.

The typescript compiler (typescript 2.0.2) does not throw errors

Your gulpfile:

gulp.task('build-ts', function () {
    return gulp.src(appDev + '**/*.ts')
        .pipe(sourcemaps.init())
        .pipe(typescript(tsProject))
        .pipe(sourcemaps.write('.',{
            sourceMappingURL: function(file) {
                return host + '/' + appProd + file.relative + '.map';
            }
        }))
        .pipe(gulp.dest(appProd));
});

The app runs fine despite these errors.

[ivogabe]

The readonly modifier is not supported in the last stable release of TypeScript (1.8). You have to install a nightly or the release candidate of 2.0 to use it, and configure it in your gulpfile. See more in the readme.

[RoxKilly]

Thanks @ivogabe . That resolved things for me. I didn't know gulp-typescript could be used with a custom typescript version.

Do you have any insight about whether this tool can be used with ngc the angular compiler? (ngc is a drop in replacement for tsc that compiles and bundles Angular typescript into JS)

Reference: https://github.com/angular/angular/tree/master/modules/%40angular/compiler-cli#install-and-use

[ivogabe]

gulp-typescript can be used with forks of TypeScript, but ngc seems to be a different program instead of a fork. So I'm afraid that ngc cannot be used with gulp-typescript, but there might be a different gulp plugin for it.