Add ability to disable lexical dep

[Manishearth]

swc uses the lexical family of crates for parsing numbers. It's a fast crate, but unfortunately it has a number of soundness issues, and so far there has been no movement from upstream on this (or accepting any of the patches opened so far):

• [BUG] Safety comments for MaybeUninit::assume_init calls are wrong, calls are UB Alexhuszagh/rust-lexical#95
• [BUG] Unsoundness: try_parse_{4,8}digits appear to advance iterators out of bounds Alexhuszagh/rust-lexical#101
• [BUG] Unsoundness in Bytes::read() Alexhuszagh/rust-lexical#102
• [BUG] BytesIter should be an unsafe trait or private Alexhuszagh/rust-lexical#104

It would be nice for users of swc to be able to choose whether lexical is used. I would recommend making lexical an optional dependency, enabled by default, so that people can use swc with no-default-features if they wish to avoid the dep. The num family of crates is well established and has alternate code that does the same stuff as lexical, though perhaps not as optimized.

We have a patch we can submit to support this.

[kdy1]

It's fine to switch to num completely, but I don't want it to be optional dep. It's too much for the maintainers

[Manishearth]

It's a relatively small patch. How about we provide both options (remove the dep completely vs make it optional) and you can choose?

[kdy1]

Who choose? Removing dep completely is fine, but I'm not sure what you are saying

[Manishearth]

Oh, I was saying that the patch to make it optional is not much more complicated and you can choose which PR to land after looking at them: whether to land the one making it optional or the one removing it completely. But if you strongly prefer removing the dep we can just do that.

[gmcsorley-work]

I've sent two pull requests:

• Make usage of lexical from swc_ecma_parser optional #7757 - This will make lexical an optional feature within swc-ecma-parser but included in the default with fallback to num-bigint if the feature is excluded.
• refactor(es/parser): Do not use lexical #7758 - This will remove all usage of lexical from swc-ecma-parser replacing it with the num-bigint implementation.

You can decide which approach you prefer.

[swc-bot]

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