ast: ContentEq for -0 vs +0

[Boshen]

Background

impl ContentEq for NumericLiteral<'_> {
    fn content_eq(&self, other: &Self) -> bool {
        ContentEq::content_eq(&self.value, &other.value)
    }
}

    macro_rules! content_eq_impl {
        ($($t:ty)*) => ($(
            impl ContentEq for $t {
                #[inline]
                fn content_eq(&self, other: &$t) -> bool { (*self) == (*other) }
                #[inline]
                fn content_ne(&self, other: &$t) -> bool { (*self) != (*other) }
            }
        )*)
    }

    content_eq_impl! {
        char &str
        bool isize usize
        u8 u16 u32 u64 u128
        i8 i16 i32 i64 i128
        f32 f64
    }

Motivation

In minifier a(b ? +0 : -0) is currently minified to a((b, 0));, but shouldn't, due to:

        if ctx.expr_eq(&expr.alternate, &expr.consequent) {
            // "a ? b : b" => "a, b"
            let expressions = ctx.ast.vec_from_array([
                ctx.ast.move_expression(&mut expr.test),
                ctx.ast.move_expression(&mut expr.consequent),
            ]);
            return Some(ctx.ast.expression_sequence(expr.span, expressions));
        }

[overlookmotel]

Should NumericLiteral ever contain a negative number? Aren't negative numbers expressed as a UnaryExpression wrapping a NumericLiteral? Playground

That's a question, not an argument! We can adapt ContentEq to handle this case no problem, but I'm wondering if we should need to, or whether the problem is best addressed elsewhere.

[Boshen]

Should NumericLiteral ever contain a negative number?

Our minifier folds unary numbers, Infinity, NaN into negative number, f64::inf and f64:NaN.

oxc/crates/oxc_minifier/src/peephole/normalize.rs

Lines 186 to 196 in 8eccdec

	"Infinity" if ident.is_global_reference(ctx.symbols()) => {
	Some(ctx.ast.expression_numeric_literal(
	ident.span,
	f64::INFINITY,
	None,
	NumberBase::Decimal,
	))
	}
	"NaN" if ident.is_global_reference(ctx.symbols()) => Some(
	ctx.ast.expression_numeric_literal(ident.span, f64::NAN, None, NumberBase::Decimal),
	),

oxc/crates/oxc_minifier/src/peephole/fold_constants.rs

Line 50 in 8eccdec

_ => ctx.eval_unary_expression(e).map(|v| ctx.value_to_expr(e.span, v)),

[overlookmotel]

Fixed in #9007.