codegen: remove underscore from bigint

[Boshen]

oxc/crates/oxc_codegen/src/gen.rs

Line 1171 in 44375a5

p.print_str(self.raw.as_str());

looks like it prints the raw val from the original source text

Good catch, underscore should be removed from codegen.

Originally posted by @Boshen in #7280 (comment)

[overlookmotel]

Please also see #7254. Of the options outlined there, personally I'd tend towards the option of removing the raw field.

In my view, the ideal solution would be to parse the BigInt's value in the parser. At that point we are running through the source text byte-by-byte anyway.

I would propose:

• Adding a value: &'a str field.
• Removing the base field.

pub struct BigIntLiteral<'a> {
    pub span: Span,
    pub value: &'a str,
    pub raw: &'a str, // Leave for now, but likely remove later
}

In parser, parse it to a &str (without underscores, converted to decimal), using code like this:

oxc/crates/oxc_ast/src/serialize.rs

Lines 68 to 93 in f0affa2

	impl<'a> From<&'a BigIntLiteral<'a>> for ESTreeLiteral<'a, ()> {
	fn from(value: &'a BigIntLiteral) -> Self {
	let src = &value.raw.strip_suffix('n').unwrap().cow_replace('_', "");
	let src = match value.base {
	BigintBase::Decimal => src,
	BigintBase::Binary | BigintBase::Octal | BigintBase::Hex => &src[2..],
	};
	let radix = match value.base {
	BigintBase::Decimal => 10,
	BigintBase::Binary => 2,
	BigintBase::Octal => 8,
	BigintBase::Hex => 16,
	};
	let bigint = BigInt::from_str_radix(src, radix).unwrap();
	Self {
	span: value.span,
	// BigInts can't be serialized to JSON
	value: (),
	raw: Some(value.raw.as_str()),
	bigint: Some(bigint.to_string()),
	regex: None,
	}
	}
	}

Then codegen can print the value field.

A bit of background: Originally BigIntLiteral had a value: BigInt field. We had to remove it because BigInt stores data on the heap, so it's not possible to make it part of the AST, as that heap data didn't get freed when the AST is dropped (memory leak). So that's why we have to store the value as a string slice (which would be stored in arena).

However, removing the underscores in codegen is an improvement on how it is now - not a bad interim solution.