Support #__PURE__ and #__NO_SIDE_EFFECTS__ notation

[Boshen]

Background: https://github.com/javascript-compiler-hints/compiler-notations-spec

[Boshen]

I propose a no_side_effects: bool field to be added to CallExpression, NewExpression, and Function. These values are set in the parser, or upon construction in the transformer, and read from in codegen and minifier.

[IWANABETHATGUY]

This method did not scale, if the downstream app required more annotation

[Boshen]

This method did not scale, if the downstream app required more annotation

Can you give us an example?

[IWANABETHATGUY]

vite has a special magic comments vite-ignore to let user explicit control bundler behavior. ref: https://github.com/rolldown/rolldown/blob/b546e53adf0d8fecbca8a9f0dddbcb44cb308a99/crates/rolldown/src/ast_scanner/new_url.rs?plain=1#L35-L43
vitejs/vite#18494, webpack also has some special meaning magic comments

[IWANABETHATGUY]

https://github.com/rolldown/rolldown/blob/b546e53adf0d8fecbca8a9f0dddbcb44cb308a99/crates/rolldown/src/ast_scanner/new_url.rs?plain=1#L35-L43, for now this code works fine when the ast is parsed from source code, but will not work if the ast is generated by transformer. If use the method you proposed, you may need to add many flag to support other widely used tools.

[IWANABETHATGUY]

What about use a hashmap to store leading comments of some generated node, the key should be their Address

[IWANABETHATGUY]

But I think your method is good enough for rolldown and vite

[Boshen]

#__PURE__ and #__NO_SIDE_EFFECTS__ has semantic meanings that affect the whole compiler pipeline, whereas other annotations don't.