Do not remove PURE comment after typed declaration

[LongTengDao]

TypeScript Version: 3.4.0-dev.201xxxxx

Search Terms:

Code

const a :Type = /*#__PURE__*/ function () {}();

Expected behavior:

const a = /*#__PURE__*/ function () {}();

Actual behavior:

const a = function () {}();

Playground Link:

Related Issues:

[AnyhowStep]

Why not make it a JSDoc?

/**
 * __PURE__
 */
const a : Type = function () {}();

Output:

/**
 * __PURE__
 */
var a = function () { }();

[AlCalzone]

This is #13721 I think

[LongTengDao]

@AnyhowStep Thanks for reply. I didn't know that. But only /*#__PURE__*/ is widely used in downstream tools, like rollup (pack tool) or uglify/terser (minify tool).

BTW: I wonder why the comment removed, it's just same line with types syntax, not same part of an expression, even not same side of assignment equal mark...

[ashi009]

@AlCalzone

This is #13721 I think

#13721 is mainly for classes, which is fixed in #16631. This is actually #7770.

@LongTengDao

A workaround is to add parentheses around the pure expression, which will preserve the comment until this is fixed.

const a : Type = (/*#__PURE__*/ function () {}());
// var a = ( /*#__PURE__*/function () { }());

[LongTengDao]

@ashi009 Oh, that works, thank you!

Anyway, I wrote my personal ts transpiler (@ ltd/j-ts) ;)

[LongTengDao]

seems fixed in 5.3

[jakebailey]

Yes, this was fixed by #47407 (and #47158 was a dupe of this one).