Sign is printed twice when formatting a negative BigInt

[ryangoree]

Describe the Bug

If you format a negative BigInt instance, the sign (-) gets printed twice.

Steps to Reproduce

1. Create a negative BigInt

   let int = BigInt::from(-1);

2. Use console_log! macro to see it's formatted with 2 signs:

   console_log!("{}", int); // --1

Minimal test repo: https://github.com/ryangoree/js-sys-bigint-display-bug

Expected Behavior

The sign would be printed once (-1).

Actual Behavior

The sign is printed twice (--1).

[ryangoree]

Looks like the problem is here:

wasm-bindgen/crates/js-sys/src/lib.rs

Line 1496 in ddceac7

f.pad_integral(self >= &BigInt::from(0), "", &self.to_string_unchecked(10))

The docs for pad_integral state:

The str should not contain the sign for the integer, that will be added by this method.

However to_string_unchecked calls toString on the bigint which returns a string with the sign:

wasm-bindgen/crates/js-sys/src/lib.rs

Lines 1349 to 1350 in ddceac7

	#[wasm_bindgen(method, js_name = toString)]
	fn to_string_unchecked(this: &BigInt, radix: u8) -> String;