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oxc/crates/oxc_minifier/src/ast_passes/peephole_fold_constants.rs

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use oxc_ast::ast::*;
use oxc_ecmascript::{
constant_evaluation::{ConstantEvaluation, ConstantValue, ValueType},
side_effects::MayHaveSideEffects,
};
use oxc_span::{GetSpan, SPAN};
use oxc_syntax::{
number::NumberBase,
operator::{BinaryOperator, LogicalOperator},
};
use oxc_traverse::{traverse_mut_with_ctx, Ancestor, ReusableTraverseCtx, Traverse, TraverseCtx};
use crate::{node_util::Ctx, CompressorPass};
/// Constant Folding
///
/// <https://github.com/google/closure-compiler/blob/v20240609/src/com/google/javascript/jscomp/PeepholeFoldConstants.java>
pub struct PeepholeFoldConstants {
pub(crate) changed: bool,
}
impl<'a> CompressorPass<'a> for PeepholeFoldConstants {
fn build(&mut self, program: &mut Program<'a>, ctx: &mut ReusableTraverseCtx<'a>) {
self.changed = false;
traverse_mut_with_ctx(self, program, ctx);
}
}
impl<'a> Traverse<'a> for PeepholeFoldConstants {
fn exit_expression(&mut self, expr: &mut Expression<'a>, ctx: &mut TraverseCtx<'a>) {
let ctx = Ctx(ctx);
if let Some(folded_expr) = match expr {
Expression::CallExpression(e) => {
Self::try_fold_useless_object_dot_define_properties_call(e, ctx)
}
Expression::NewExpression(e) => Self::try_fold_ctor_cal(e, ctx),
// TODO
// return tryFoldSpread(subtree);
Expression::ArrayExpression(e) => Self::try_flatten_array_expression(e, ctx),
Expression::ObjectExpression(e) => Self::try_flatten_object_expression(e, ctx),
Expression::BinaryExpression(e) => Self::try_fold_binary_expression(e, ctx),
#[allow(clippy::float_cmp)]
Expression::UnaryExpression(e) => {
match e.operator {
// Do not fold `void 0` back to `undefined`.
UnaryOperator::Void if e.argument.is_number_0() => None,
// Do not fold `true` and `false` back to `!0` and `!1`
UnaryOperator::LogicalNot if matches!(&e.argument, Expression::NumericLiteral(lit) if lit.value == 0.0 || lit.value == 1.0) => {
None
}
_ => ctx.eval_unary_expression(e).map(|v| ctx.value_to_expr(e.span, v)),
}
}
// TODO: return tryFoldGetProp(subtree);
Expression::LogicalExpression(e) => Self::try_fold_logical_expression(e, ctx),
Expression::ChainExpression(e) => Self::try_fold_optional_chain(e, ctx),
// TODO: tryFoldGetElem
// TODO: tryFoldAssign
_ => None,
} {
*expr = folded_expr;
self.changed = true;
};
}
}
impl<'a, 'b> PeepholeFoldConstants {
pub fn new() -> Self {
Self { changed: false }
}
fn try_fold_useless_object_dot_define_properties_call(
_call_expr: &mut CallExpression<'a>,
_ctx: Ctx<'a, '_>,
) -> Option<Expression<'a>> {
None
}
fn try_fold_ctor_cal(
_new_expr: &mut NewExpression<'a>,
_ctx: Ctx<'a, '_>,
) -> Option<Expression<'a>> {
None
}
fn try_flatten_array_expression(
_new_expr: &mut ArrayExpression<'a>,
_ctx: Ctx<'a, 'b>,
) -> Option<Expression<'a>> {
None
}
fn try_flatten_object_expression(
_new_expr: &mut ObjectExpression<'a>,
_ctx: Ctx<'a, 'b>,
) -> Option<Expression<'a>> {
None
}
fn try_fold_logical_expression(
logical_expr: &mut LogicalExpression<'a>,
ctx: Ctx<'a, 'b>,
) -> Option<Expression<'a>> {
match logical_expr.operator {
LogicalOperator::And | LogicalOperator::Or => Self::try_fold_and_or(logical_expr, ctx),
LogicalOperator::Coalesce => Self::try_fold_coalesce(logical_expr, ctx),
}
}
fn try_fold_optional_chain(
chain_expr: &mut ChainExpression<'a>,
ctx: Ctx<'a, 'b>,
) -> Option<Expression<'a>> {
let member_expr = chain_expr.expression.as_member_expression()?;
if !member_expr.optional() {
return None;
}
let object = member_expr.object();
let ty = ValueType::from(object);
(ty.is_null() || ty.is_undefined())
.then(|| ctx.value_to_expr(chain_expr.span, ConstantValue::Undefined))
}
/// Try to fold a AND / OR node.
///
/// port from [closure-compiler](https://github.com/google/closure-compiler/blob/09094b551915a6487a980a783831cba58b5739d1/src/com/google/javascript/jscomp/PeepholeFoldConstants.java#L587)
pub fn try_fold_and_or(
logical_expr: &mut LogicalExpression<'a>,
ctx: Ctx<'a, 'b>,
) -> Option<Expression<'a>> {
let op = logical_expr.operator;
debug_assert!(matches!(op, LogicalOperator::And | LogicalOperator::Or));
let left = &logical_expr.left;
let left_val = ctx.get_boolean_value(left);
if let Some(lval) = left_val {
// Bail `0 && (module.exports = {})` for `cjs-module-lexer`.
if !lval {
if let Expression::AssignmentExpression(assign_expr) = &logical_expr.right {
if let Some(member_expr) = assign_expr.left.as_member_expression() {
if member_expr.is_specific_member_access("module", "exports") {
return None;
}
}
}
}
// (TRUE || x) => TRUE (also, (3 || x) => 3)
// (FALSE && x) => FALSE
if if lval { op == LogicalOperator::Or } else { op == LogicalOperator::And } {
return Some(ctx.ast.move_expression(&mut logical_expr.left));
} else if !left.may_have_side_effects() {
let parent = ctx.ancestry.parent();
// Bail `let o = { f() { assert.ok(this !== o); } }; (true && o.f)(); (true && o.f)``;`
if parent.is_tagged_template_expression()
|| matches!(parent, Ancestor::CallExpressionCallee(_))
{
return None;
}
// (FALSE || x) => x
// (TRUE && x) => x
return Some(ctx.ast.move_expression(&mut logical_expr.right));
}
// Left side may have side effects, but we know its boolean value.
// e.g. true_with_sideeffects || foo() => true_with_sideeffects, foo()
// or: false_with_sideeffects && foo() => false_with_sideeffects, foo()
let left = ctx.ast.move_expression(&mut logical_expr.left);
let right = ctx.ast.move_expression(&mut logical_expr.right);
let vec = ctx.ast.vec_from_array([left, right]);
let sequence_expr = ctx.ast.expression_sequence(logical_expr.span, vec);
return Some(sequence_expr);
} else if let Expression::LogicalExpression(left_child) = &mut logical_expr.left {
if left_child.operator == logical_expr.operator {
let left_child_right_boolean = ctx.get_boolean_value(&left_child.right);
let left_child_op = left_child.operator;
if let Some(right_boolean) = left_child_right_boolean {
if !left_child.right.may_have_side_effects() {
// a || false || b => a || b
// a && true && b => a && b
if !right_boolean && left_child_op == LogicalOperator::Or
|| right_boolean && left_child_op == LogicalOperator::And
{
let left = ctx.ast.move_expression(&mut left_child.left);
let right = ctx.ast.move_expression(&mut logical_expr.right);
let logic_expr = ctx.ast.expression_logical(
logical_expr.span,
left,
left_child_op,
right,
);
return Some(logic_expr);
}
}
}
}
}
None
}
/// Try to fold a nullish coalesce `foo ?? bar`.
pub fn try_fold_coalesce(
logical_expr: &mut LogicalExpression<'a>,
ctx: Ctx<'a, 'b>,
) -> Option<Expression<'a>> {
debug_assert_eq!(logical_expr.operator, LogicalOperator::Coalesce);
let left = &logical_expr.left;
let left_val = ValueType::from(left);
match left_val {
ValueType::Null | ValueType::Undefined => {
Some(if left.may_have_side_effects() {
// e.g. `(a(), null) ?? 1` => `(a(), null, 1)`
let expressions = ctx.ast.vec_from_array([
ctx.ast.move_expression(&mut logical_expr.left),
ctx.ast.move_expression(&mut logical_expr.right),
]);
ctx.ast.expression_sequence(SPAN, expressions)
} else {
// nullish condition => this expression evaluates to the right side.
ctx.ast.move_expression(&mut logical_expr.right)
})
}
ValueType::Number
| ValueType::BigInt
| ValueType::String
| ValueType::Boolean
| ValueType::Object => {
// non-nullish condition => this expression evaluates to the left side.
Some(ctx.ast.move_expression(&mut logical_expr.left))
}
ValueType::Undetermined => None,
}
}
fn try_fold_binary_expression(
e: &mut BinaryExpression<'a>,
ctx: Ctx<'a, 'b>,
) -> Option<Expression<'a>> {
// TODO: tryReduceOperandsForOp
match e.operator {
BinaryOperator::ShiftLeft
| BinaryOperator::ShiftRight
| BinaryOperator::ShiftRightZeroFill
| BinaryOperator::Addition
| BinaryOperator::Subtraction
| BinaryOperator::Division
| BinaryOperator::Remainder
| BinaryOperator::Multiplication
| BinaryOperator::Exponential => {
ctx.eval_binary_expression(e).map(|v| ctx.value_to_expr(e.span, v))
}
BinaryOperator::BitwiseAnd | BinaryOperator::BitwiseOR | BinaryOperator::BitwiseXOR => {
if let Some(v) = ctx.eval_binary_expression(e) {
return Some(ctx.value_to_expr(e.span, v));
}
Self::try_fold_left_child_op(e, ctx)
}
op if op.is_equality() || op.is_compare() => Self::try_fold_comparison(e, ctx),
_ => None,
}
}
fn try_fold_left_child_op(
e: &mut BinaryExpression<'a>,
ctx: Ctx<'a, '_>,
) -> Option<Expression<'a>> {
let op = e.operator;
debug_assert!(matches!(
op,
BinaryOperator::BitwiseAnd | BinaryOperator::BitwiseOR | BinaryOperator::BitwiseXOR
));
let Expression::BinaryExpression(left) = &mut e.left else {
return None;
};
if left.operator != op {
return None;
}
let (v, expr_to_move);
if let Some(result) = ctx.eval_binary_operation(op, &left.left, &e.right) {
(v, expr_to_move) = (result, &mut left.right);
} else if let Some(result) = ctx.eval_binary_operation(op, &left.right, &e.right) {
(v, expr_to_move) = (result, &mut left.left);
} else {
return None;
}
Some(ctx.ast.expression_binary(
e.span,
ctx.ast.move_expression(expr_to_move),
op,
ctx.value_to_expr(Span::new(left.right.span().start, e.right.span().end), v),
))
}
fn try_fold_comparison(e: &BinaryExpression<'a>, ctx: Ctx<'a, 'b>) -> Option<Expression<'a>> {
let left = &e.left;
let right = &e.right;
let op = e.operator;
if left.may_have_side_effects() || right.may_have_side_effects() {
return None;
}
let value = match op {
BinaryOperator::LessThan
| BinaryOperator::GreaterThan
| BinaryOperator::LessEqualThan
| BinaryOperator::GreaterEqualThan => {
return ctx.eval_binary_expression(e).map(|v| ctx.value_to_expr(e.span, v));
}
BinaryOperator::Equality => Self::try_abstract_equality_comparison(left, right, ctx),
BinaryOperator::Inequality => {
Self::try_abstract_equality_comparison(left, right, ctx).map(|b| !b)
}
BinaryOperator::StrictEquality => {
Self::try_strict_equality_comparison(left, right, ctx)
}
BinaryOperator::StrictInequality => {
Self::try_strict_equality_comparison(left, right, ctx).map(|b| !b)
}
_ => None,
};
let value = match value {
Some(true) => true,
Some(false) => false,
None => return None,
};
Some(ctx.ast.expression_boolean_literal(e.span, value))
}
/// <https://tc39.es/ecma262/#sec-abstract-equality-comparison>
fn try_abstract_equality_comparison(
left_expr: &'b Expression<'a>,
right_expr: &'b Expression<'a>,
ctx: Ctx<'a, 'b>,
) -> Option<bool> {
let left = ValueType::from(left_expr);
let right = ValueType::from(right_expr);
if left != ValueType::Undetermined && right != ValueType::Undetermined {
if left == right {
return Self::try_strict_equality_comparison(left_expr, right_expr, ctx);
}
if matches!(
(left, right),
(ValueType::Null, ValueType::Undefined) | (ValueType::Undefined, ValueType::Null)
) {
return Some(true);
}
if matches!((left, right), (ValueType::Number, ValueType::String))
|| matches!(right, ValueType::Boolean)
{
let right_number = ctx.get_side_free_number_value(right_expr);
if let Some(num) = right_number {
let number_literal_expr = ctx.ast.expression_numeric_literal(
right_expr.span(),
num,
None,
if num.fract() == 0.0 { NumberBase::Decimal } else { NumberBase::Float },
);
return Self::try_abstract_equality_comparison(
left_expr,
&number_literal_expr,
ctx,
);
}
return None;
}
if matches!((left, right), (ValueType::String, ValueType::Number))
|| matches!(left, ValueType::Boolean)
{
let left_number = ctx.get_side_free_number_value(left_expr);
if let Some(num) = left_number {
let number_literal_expr = ctx.ast.expression_numeric_literal(
left_expr.span(),
num,
None,
if num.fract() == 0.0 { NumberBase::Decimal } else { NumberBase::Float },
);
return Self::try_abstract_equality_comparison(
&number_literal_expr,
right_expr,
ctx,
);
}
return None;
}
if matches!(left, ValueType::BigInt) || matches!(right, ValueType::BigInt) {
let left_bigint = ctx.get_side_free_bigint_value(left_expr);
let right_bigint = ctx.get_side_free_bigint_value(right_expr);
if let (Some(l_big), Some(r_big)) = (left_bigint, right_bigint) {
return Some(l_big.eq(&r_big));
}
}
if matches!(left, ValueType::String | ValueType::Number | ValueType::BigInt)
&& matches!(right, ValueType::Object)
{
return None;
}
if matches!(left, ValueType::Object)
&& matches!(right, ValueType::String | ValueType::Number | ValueType::BigInt)
{
return None;
}
return Some(false);
}
None
}
/// <https://tc39.es/ecma262/#sec-strict-equality-comparison>
#[expect(clippy::float_cmp)]
fn try_strict_equality_comparison(
left_expr: &'b Expression<'a>,
right_expr: &'b Expression<'a>,
ctx: Ctx<'a, 'b>,
) -> Option<bool> {
let left = ValueType::from(left_expr);
let right = ValueType::from(right_expr);
if left != ValueType::Undetermined && right != ValueType::Undetermined {
// Strict equality can only be true for values of the same type.
if left != right {
return Some(false);
}
return match left {
ValueType::Number => {
let left_number = ctx.get_side_free_number_value(left_expr);
let right_number = ctx.get_side_free_number_value(right_expr);
if let (Some(l_num), Some(r_num)) = (left_number, right_number) {
if l_num.is_nan() || r_num.is_nan() {
return Some(false);
}
return Some(l_num == r_num);
}
None
}
ValueType::String => {
let left_string = ctx.get_side_free_string_value(left_expr);
let right_string = ctx.get_side_free_string_value(right_expr);
if let (Some(left_string), Some(right_string)) = (left_string, right_string) {
return Some(left_string == right_string);
}
None
}
ValueType::Undefined | ValueType::Null => Some(true),
ValueType::Boolean if right.is_boolean() => {
let left = ctx.get_boolean_value(left_expr);
let right = ctx.get_boolean_value(right_expr);
if let (Some(left_bool), Some(right_bool)) = (left, right) {
return Some(left_bool == right_bool);
}
None
}
// TODO
ValueType::BigInt
| ValueType::Object
| ValueType::Boolean
| ValueType::Undetermined => None,
};
}
// Then, try to evaluate based on the value of the expression.
// There's only one special case:
// Any strict equality comparison against NaN returns false.
if left_expr.is_nan() || right_expr.is_nan() {
return Some(false);
}
None
}
}
/// <https://github.com/google/closure-compiler/blob/v20240609/test/com/google/javascript/jscomp/PeepholeFoldConstantsTest.java>
#[cfg(test)]
mod test {
use oxc_allocator::Allocator;
static MAX_SAFE_FLOAT: f64 = 9_007_199_254_740_991_f64;
static NEG_MAX_SAFE_FLOAT: f64 = -9_007_199_254_740_991_f64;
static MAX_SAFE_INT: i64 = 9_007_199_254_740_991_i64;
static NEG_MAX_SAFE_INT: i64 = -9_007_199_254_740_991_i64;
use crate::tester;
fn test(source_text: &str, expected: &str) {
let allocator = Allocator::default();
let mut pass = super::PeepholeFoldConstants::new();
tester::test(&allocator, source_text, expected, &mut pass);
}
fn test_nospace(source_text: &str, expected: &str) {
let allocator = Allocator::default();
let mut pass = super::PeepholeFoldConstants::new();
tester::test_impl(&allocator, source_text, expected, &mut pass, true);
}
fn test_same(source_text: &str) {
test(source_text, source_text);
}
#[test]
fn undefined_comparison1() {
test("undefined == undefined", "true");
test("undefined == null", "true");
test("undefined == void 0", "true");
test("undefined == 0", "false");
test("undefined == 1", "false");
test("undefined == 'hi'", "false");
test("undefined == true", "false");
test("undefined == false", "false");
test("undefined === undefined", "true");
test("undefined === null", "false");
test("undefined === void 0", "true");
test_same("undefined == this");
test_same("undefined == x");
test("undefined != undefined", "false");
test("undefined != null", "false");
test("undefined != void 0", "false");
test("undefined != 0", "true");
test("undefined != 1", "true");
test("undefined != 'hi'", "true");
test("undefined != true", "true");
test("undefined != false", "true");
test("undefined !== undefined", "false");
test("undefined !== void 0", "false");
test("undefined !== null", "true");
test_same("undefined != this");
test_same("undefined != x");
test("undefined < undefined", "false");
test("undefined > undefined", "false");
test("undefined >= undefined", "false");
test("undefined <= undefined", "false");
test("0 < undefined", "false");
test("true > undefined", "false");
test("'hi' >= undefined", "false");
test("null <= undefined", "false");
test("undefined < 0", "false");
test("undefined > true", "false");
test("undefined >= 'hi'", "false");
test("undefined <= null", "false");
test("null == undefined", "true");
test("0 == undefined", "false");
test("1 == undefined", "false");
test("'hi' == undefined", "false");
test("true == undefined", "false");
test("false == undefined", "false");
test("null === undefined", "false");
test("void 0 === undefined", "true");
test("undefined == NaN", "false");
test("NaN == undefined", "false");
test("undefined == Infinity", "false");
test("Infinity == undefined", "false");
test("undefined == -Infinity", "false");
test("-Infinity == undefined", "false");
test("({}) == undefined", "false");
test("undefined == ({})", "false");
test("([]) == undefined", "false");
test("undefined == ([])", "false");
test("(/a/g) == undefined", "false");
test("undefined == (/a/g)", "false");
test("(function(){}) == undefined", "false");
test("undefined == (function(){})", "false");
test("undefined != NaN", "true");
test("NaN != undefined", "true");
test("undefined != Infinity", "true");
test("Infinity != undefined", "true");
test("undefined != -Infinity", "true");
test("-Infinity != undefined", "true");
test("({}) != undefined", "true");
test("undefined != ({})", "true");
test("([]) != undefined", "true");
test("undefined != ([])", "true");
test("(/a/g) != undefined", "true");
test("undefined != (/a/g)", "true");
test("(function(){}) != undefined", "true");
test("undefined != (function(){})", "true");
test_same("this == undefined");
test_same("x == undefined");
}
#[test]
fn test_undefined_comparison2() {
test("\"123\" !== void 0", "true");
test("\"123\" === void 0", "false");
test("void 0 !== \"123\"", "true");
test("void 0 === \"123\"", "false");
}
#[test]
fn test_undefined_comparison3() {
test("\"123\" !== undefined", "true");
test("\"123\" === undefined", "false");
test("undefined !== \"123\"", "true");
test("undefined === \"123\"", "false");
}
#[test]
fn test_null_comparison1() {
test("null == undefined", "true");
test("null == null", "true");
test("null == void 0", "true");
test("null == 0", "false");
test("null == 1", "false");
// test("null == 0n", "false");
// test("null == 1n", "false");
test("null == 'hi'", "false");
test("null == true", "false");
test("null == false", "false");
test("null === undefined", "false");
test("null === null", "true");
test("null === void 0", "false");
test_same("null===x");
test_same("null==this");
test_same("null==x");
test("null != undefined", "false");
test("null != null", "false");
test("null != void 0", "false");
test("null != 0", "true");
test("null != 1", "true");
// test("null != 0n", "true");
// test("null != 1n", "true");
test("null != 'hi'", "true");
test("null != true", "true");
test("null != false", "true");
test("null !== undefined", "true");
test("null !== void 0", "true");
test("null !== null", "false");
test_same("null!=this");
test_same("null!=x");
test("null < null", "false");
test("null > null", "false");
test("null >= null", "true");
test("null <= null", "true");
test("0 < null", "false");
test("0 > null", "false");
test("0 >= null", "true");
// test("0n < null", "false");
// test("0n > null", "false");
// test("0n >= null", "true");
test("true > null", "true");
test("'hi' < null", "false");
test("'hi' >= null", "false");
test("null <= null", "true");
test("null < 0", "false");
// test("null < 0n", "false");
test("null > true", "false");
test("null < 'hi'", "false");
test("null >= 'hi'", "false");
test("null <= null", "true");
test("null == null", "true");
test("0 == null", "false");
test("1 == null", "false");
test("'hi' == null", "false");
test("true == null", "false");
test("false == null", "false");
test("null === null", "true");
test("void 0 === null", "false");
test("null == NaN", "false");
test("NaN == null", "false");
test("null == Infinity", "false");
test("Infinity == null", "false");
test("null == -Infinity", "false");
test("-Infinity == null", "false");
test("({}) == null", "false");
test("null == ({})", "false");
test("([]) == null", "false");
test("null == ([])", "false");
test("(/a/g) == null", "false");
test("null == (/a/g)", "false");
test("(function(){}) == null", "false");
test("null == (function(){})", "false");
test("null != NaN", "true");
test("NaN != null", "true");
test("null != Infinity", "true");
test("Infinity != null", "true");
test("null != -Infinity", "true");
test("-Infinity != null", "true");
test("({}) != null", "true");
test("null != ({})", "true");
test("([]) != null", "true");
test("null != ([])", "true");
test("(/a/g) != null", "true");
test("null != (/a/g)", "true");
test("(function(){}) != null", "true");
test("null != (function(){})", "true");
test_same("({a:f()})==null");
test_same("null=={a:f()}");
test_same("[f()]==null");
test_same("null==[f()]");
test_same("this==null");
test_same("x==null");
}
#[test]
fn test_boolean_boolean_comparison() {
test_same("!x==!y");
test_same("!x<!y");
test_same("!x!==!y");
test_same("!x==!x"); // foldable
test_same("!x<!x"); // foldable
test_same("!x!==!x"); // foldable
}
#[test]
fn test_boolean_number_comparison() {
test_same("!x==+y");
test_same("!x<=+y");
test_same("!x !== +y");
}
#[test]
fn test_number_boolean_comparison() {
test_same("+x==!y");
test_same("+x<=!y");
test_same("+x === !y");
}
#[test]
fn test_boolean_string_comparison() {
test_same("!x==''+y");
test_same("!x<=''+y");
test_same("!x !== '' + y");
}
#[test]
fn test_string_boolean_comparison() {
test_same("''+x==!y");
test_same("''+x<=!y");
test_same("'' + x === !y");
}
#[test]
fn test_string_string_comparison() {
test("'a' < 'b'", "true");
test("'a' <= 'b'", "true");
test("'a' > 'b'", "false");
test("'a' >= 'b'", "false");
test("+'a' < +'b'", "false");
test_same("typeof a < 'a'");
test_same("'a' >= typeof a");
test_same("typeof a < typeof a");
test_same("typeof a >= typeof a");
test("typeof 3 > typeof 4", "false");
test("typeof function() {} < typeof function() {}", "false");
test("'a' == 'a'", "true");
test("'b' != 'a'", "true");
test_same("'undefined' == typeof a");
test_same("typeof a != 'number'");
test_same("'undefined' == typeof a");
test_same("'undefined' == typeof a");
test_same("typeof a == typeof a");
test("'a' === 'a'", "true");
test("'b' !== 'a'", "true");
test_same("typeof a === typeof a");
test_same("typeof a !== typeof a");
test_same("'' + x <= '' + y");
test_same("'' + x != '' + y");
test_same("'' + x === '' + y");
test_same("'' + x <= '' + x"); // potentially foldable
test_same("'' + x != '' + x"); // potentially foldable
test_same("'' + x === '' + x"); // potentially foldable
test(r#"if (" str ing " !== "\u000Bstr\u000Bing\u000B") {}"#, "if (false) {}\n");
}
#[test]
fn test_number_string_comparison() {
test("1 < '2'", "true");
test("2 > '1'", "true");
test("123 > '34'", "true");
test("NaN >= 'NaN'", "false");
test("1 == '2'", "false");
test("1 != '1'", "false");
test("NaN == 'NaN'", "false");
test("1 === '1'", "false");
test("1 !== '1'", "true");
test_same("+x>''+y");
test_same("+x==''+y");
test_same("+x !== '' + y");
}
#[test]
fn test_string_number_comparison() {
test("'1' < 2", "true");
test("'2' > 1", "true");
test("'123' > 34", "true");
test("'NaN' < NaN", "false");
test("'1' == 2", "false");
test("'1' != 1", "false");
test("'NaN' == NaN", "false");
test("'1' === 1", "false");
test("'1' !== 1", "true");
test_same("''+x<+y");
test_same("''+x==+y");
test_same("'' + x === +y");
}
#[test]
#[ignore]
fn test_bigint_number_comparison() {
test("1n < 2", "true");
test("1n > 2", "false");
test("1n == 1", "true");
test("1n == 2", "false");
// comparing with decimals is allowed
test("1n < 1.1", "true");
test("1n < 1.9", "true");
test("1n < 0.9", "false");
test("-1n < -1.1", "false");
test("-1n < -1.9", "false");
test("-1n < -0.9", "true");
test("1n > 1.1", "false");
test("1n > 0.9", "true");
test("-1n > -1.1", "true");
test("-1n > -0.9", "false");
// Don't fold unsafely large numbers because there might be floating-point error
test(&format!("0n > {MAX_SAFE_INT}"), "false");
test(&format!("0n < {MAX_SAFE_INT}"), "true");
test(&format!("0n > {NEG_MAX_SAFE_INT}"), "true");
test(&format!("0n < {NEG_MAX_SAFE_INT}"), "false");
test(&format!("0n > {MAX_SAFE_FLOAT}"), "false");
test(&format!("0n < {MAX_SAFE_FLOAT}"), "true");
test(&format!("0n > {NEG_MAX_SAFE_FLOAT}"), "true");
test(&format!("0n < {NEG_MAX_SAFE_FLOAT}"), "false");
// comparing with Infinity is allowed
test("1n < Infinity", "true");
test("1n > Infinity", "false");
test("1n < -Infinity", "false");
test("1n > -Infinity", "true");
// null is interpreted as 0 when comparing with bigint
// test("1n < null", "false");
// test("1n > null", "true");
}
#[test]
#[ignore]
fn test_bigint_string_comparison() {
test("1n < '2'", "true");
test("2n > '1'", "true");
test("123n > '34'", "true");
test("1n == '1'", "true");
test("1n == '2'", "false");
test("1n != '1'", "false");
test("1n === '1'", "false");
test("1n !== '1'", "true");
}
#[test]
#[ignore]
fn test_string_bigint_comparison() {
test("'1' < 2n", "true");
test("'2' > 1n", "true");
test("'123' > 34n", "true");
test("'1' == 1n", "true");
test("'1' == 2n", "false");
test("'1' != 1n", "false");
test("'1' === 1n", "false");
test("'1' !== 1n", "true");
}
#[test]
fn test_object_bigint_comparison() {
test_same("{ valueOf: function() { return 0n; } } != 0n");
test_same("0n != { valueOf: function() { return 0n; } }");
test_same("0n != { toString: function() { return '0'; } }");
}
#[test]
fn test_nan_comparison() {
test("NaN < 1", "false");
test("NaN <= 1", "false");
test("NaN > 1", "false");
test("NaN >= 1", "false");
// test("NaN < 1n", "false");
// test("NaN <= 1n", "false");
// test("NaN > 1n", "false");
// test("NaN >= 1n", "false");
test("NaN < NaN", "false");
test("NaN >= NaN", "false");
test("NaN == NaN", "false");
test("NaN === NaN", "false");
test("NaN < null", "false");
test("null >= NaN", "false");
test("NaN == null", "false");
test("null != NaN", "true");
test("null === NaN", "false");
test("NaN < undefined", "false");
test("undefined >= NaN", "false");
test("NaN == undefined", "false");
test("undefined != NaN", "true");
test("undefined === NaN", "false");
test_same("NaN<x");
test_same("x>=NaN");
test_same("NaN==x");
test_same("x!=NaN");
test_same("NaN === x");
test_same("x !== NaN");
test_same("NaN==foo()");
}
#[test]
fn js_typeof() {
test("x = typeof 1", "x = \"number\"");
test("x = typeof 'foo'", "x = \"string\"");
test("x = typeof true", "x = \"boolean\"");
test("x = typeof false", "x = \"boolean\"");
test("x = typeof null", "x = \"object\"");
test("x = typeof undefined", "x = \"undefined\"");
test("x = typeof void 0", "x = \"undefined\"");
test("x = typeof []", "x = \"object\"");
test("x = typeof [1]", "x = \"object\"");
test("x = typeof [1,[]]", "x = \"object\"");
test("x = typeof {}", "x = \"object\"");
test("x = typeof function() {}", "x = 'function'");
test_same("x = typeof[1,[foo()]]");
test_same("x = typeof{bathwater:baby()}");
}
#[test]
fn unary_ops() {
// TODO: need to port
// These cases are handled by PeepholeRemoveDeadCode in closure-compiler.
// test_same("!foo()");
// test_same("~foo()");
// test_same("-foo()");
// These cases are handled here.
test("a=!true", "a=false");
test("a=!10", "a=false");
test("a=!false", "a=true");
test_same("a=!foo()");
// test("a=-0", "a=-0.0");
// test("a=-(0)", "a=-0.0");
test_same("a=-Infinity");
test("a=-NaN", "a=NaN");
test_same("a=-foo()");
test("a=~~0", "a=0");
test("a=~~10", "a=10");
test("a=~-7", "a=6");
test_same("a=~~foo()");
// test("a=+true", "a=1");
test("a=+10", "a=10");
// test("a=+false", "a=0");
test_same("a=+foo()");
test_same("a=+f");
// test("a=+(f?true:false)", "a=+(f?1:0)");
test("a=+0", "a=0");
test("a=+Infinity", "a=Infinity");
test("a=+NaN", "a=NaN");
test("a=+-7", "a=-7");
// test("a=+.5", "a=.5");
test("a=~0xffffffff", "a=0");
test("a=~~0xffffffff", "a=-1");
// test_same("a=~.5", PeepholeFoldConstants.FRACTIONAL_BITWISE_OPERAND);
}
#[test]
fn unary_with_big_int() {
test("-(1n)", "-1n");
test("- -1n", "1n");
test("!1n", "false");
test("~0n", "-1n");
test("~-1n", "0n");
test("~~1n", "1n");
test("~0x3n", "-4n");
test("~0b11n", "-4n");
}
#[test]
fn test_unary_ops_string_compare() {
test_same("a = -1");
test("a = ~0", "a = -1");
test("a = ~1", "a = -2");
test("a = ~101", "a = -102");
test("a = ~1.1", "a = -2");
test("a = ~0x3", "a = -4"); // Hexadecimal number
test("a = ~9", "a = -10"); // Despite `-10` is longer than `~9`, the compiler still folds it.
test_same("a = ~b");
test("a = ~NaN", "a = -1");
test("a = ~-Infinity", "a = -1");
test("x = ~2147483658.0", "x = 2147483637");
test("x = ~-2147483658", "x = -2147483639");
}
#[test]
fn test_fold_logical_op() {
test("x = true && x", "x = x");
test("x = [foo()] && x", "x = ([foo()],x)");
test("x = false && x", "x = false");
test("x = true || x", "x = true");
test("x = false || x", "x = x");
test("x = 0 && x", "x = 0");
test("x = 3 || x", "x = 3");
test("x = 0n && x", "x = 0n");
test("x = 3n || x", "x = 3n");
test("x = false || 0", "x = 0");
// unfoldable, because the right-side may be the result
test("a = x && true", "a=x && true");
test("a = x && false", "a=x && false");
test("a = x || 3", "a=x || 3");
test("a = x || false", "a=x || false");
test("a = b ? c : x || false", "a=b ? c:x || false");
test("a = b ? x || false : c", "a=b ? x || false:c");
test("a = b ? c : x && true", "a=b ? c:x && true");
test("a = b ? x && true : c", "a=b ? x && true:c");
// folded, but not here.
test_same("a = x || false ? b : c");
test_same("a = x && true ? b : c");
test("x = foo() || true || bar()", "x = foo() || true");
test("x = foo() || true && bar()", "x = foo() || bar()");
test("x = foo() || false && bar()", "x = foo() || false");
test("x = foo() && false && bar()", "x = foo() && false");
test("x = foo() && false || bar()", "x = (foo() && false,bar())");
test("x = foo() || false || bar()", "x = foo() || bar()");
test("x = foo() && true && bar()", "x = foo() && bar()");
test("x = foo() || true || bar()", "x = foo() || true");
test("x = foo() && false && bar()", "x = foo() && false");
test("x = foo() && 0 && bar()", "x = foo() && 0");
test("x = foo() && 1 && bar()", "x = foo() && bar()");
test("x = foo() || 0 || bar()", "x = foo() || bar()");
test("x = foo() || 1 || bar()", "x = foo() || 1");
test("x = foo() && 0n && bar()", "x = foo() && 0n");
test("x = foo() && 1n && bar()", "x = foo() && bar()");
test("x = foo() || 0n || bar()", "x = foo() || bar()");
test("x = foo() || 1n || bar()", "x = foo() || 1n");
test_same("x = foo() || bar() || baz()");
test_same("x = foo() && bar() && baz()");
test("0 || b()", "b()");
test("1 && b()", "b()");
test("a() && (1 && b())", "a() && b()");
test("(a() && 1) && b()", "a() && b()");
test("(x || '') || y;", "x || y");
test("false || (x || '');", "x || ''");
test("(x && 1) && y;", "x && y");
test("true && (x && 1);", "x && 1");
// Really not foldable, because it would change the type of the
// expression if foo() returns something truthy but not true.
// Cf. FoldConstants.tryFoldAndOr().
// An example would be if foo() is 1 (truthy) and bar() is 0 (falsey):
// (1 && true) || 0 == true
// 1 || 0 == 1, but true =/= 1
test_same("x = foo() && true || bar()");
test_same("foo() && true || bar()");
}
#[test]
fn test_fold_logical_op2() {
test("x = function(){} && x", "x=x");
test("x = true && function(){}", "x=function(){}");
test("x = [(function(){alert(x)})()] && x", "x=([function(){alert(x)}()],x)");
}
#[test]
fn test_fold_nullish_coalesce() {
// fold if left is null/undefined
test("null ?? 1", "1");
test("undefined ?? false", "false");
test("(a(), null) ?? 1", "(a(), null, 1)");
test("x = [foo()] ?? x", "x = [foo()]");
// short circuit on all non nullish LHS
test("x = false ?? x", "x = false");
test("x = true ?? x", "x = true");
test("x = 0 ?? x", "x = 0");
test("x = 3 ?? x", "x = 3");
// unfoldable, because the right-side may be the result
test_same("a = x ?? true");
test_same("a = x ?? false");
test_same("a = x ?? 3");
test_same("a = b ? c : x ?? false");
test_same("a = b ? x ?? false : c");
// folded, but not here.
test_same("a = x ?? false ? b : c");
test_same("a = x ?? true ? b : c");
test_same("x = foo() ?? true ?? bar()");
test("x = foo() ?? (true && bar())", "x = foo() ?? bar()");
test_same("x = (foo() || false) ?? bar()");
test("a() ?? (1 ?? b())", "a() ?? 1");
test("(a() ?? 1) ?? b()", "a() ?? 1 ?? b()");
}
#[test]
fn test_fold_void() {
test_same("void 0");
test("void 1", "void 0");
test_same("void x");
test_same("void x()");
}
#[test]
fn test_fold_opt_chain() {
// can't fold when optional part may execute
test_same("a = x?.y");
test_same("a = x?.()");
// fold args of optional call
test("x = foo() ?. (true && bar())", "x = foo() ?.(bar())");
test("a() ?. (1 ?? b())", "a() ?. (1)");
// test("({a})?.a.b.c.d()?.x.y.z", "a.b.c.d()?.x.y.z");
test("x = undefined?.y", "x = void 0");
test("x = null?.y", "x = void 0");
test("x = undefined?.[foo]", "x = void 0");
test("x = null?.[foo]", "x = void 0");
}
#[test]
fn test_fold_bitwise_op() {
test("x = 1 & 1", "x = 1");
test("x = 1 & 2", "x = 0");
test("x = 3 & 1", "x = 1");
test("x = 3 & 3", "x = 3");
test("x = 1 | 1", "x = 1");
test("x = 1 | 2", "x = 3");
test("x = 3 | 1", "x = 3");
test("x = 3 | 3", "x = 3");
test("x = 1 ^ 1", "x = 0");
test("x = 1 ^ 2", "x = 3");
test("x = 3 ^ 1", "x = 2");
test("x = 3 ^ 3", "x = 0");
test("x = -1 & 0", "x = 0");
test("x = 0 & -1", "x = 0");
test("x = 1 & 4", "x = 0");
test("x = 2 & 3", "x = 2");
// make sure we fold only when we are supposed to -- not when doing so would
// lose information or when it is performed on nonsensical arguments.
test("x = 1 & 1.1", "x = 1");
test("x = 1.1 & 1", "x = 1");
test("x = 1 & 3000000000", "x = 0");
test("x = 3000000000 & 1", "x = 0");
// Try some cases with | as well
test("x = 1 | 4", "x = 5");
test("x = 1 | 3", "x = 3");
test("x = 1 | 1.1", "x = 1");
// test_same("x = 1 | 3e9");
// these cases look strange because bitwise OR converts unsigned numbers to be signed
test("x = 1 | 3000000001", "x = -1294967295");
test("x = 4294967295 | 0", "x = -1");
}
#[test]
fn test_fold_bitwise_op2() {
test("x = y & 1 & 1", "x = y & 1");
test("x = y & 1 & 2", "x = y & 0");
test("x = y & 3 & 1", "x = y & 1");
test("x = 3 & y & 1", "x = y & 1");
test("x = y & 3 & 3", "x = y & 3");
test("x = 3 & y & 3", "x = y & 3");
test("x = y | 1 | 1", "x = y | 1");
test("x = y | 1 | 2", "x = y | 3");
test("x = y | 3 | 1", "x = y | 3");
test("x = 3 | y | 1", "x = y | 3");
test("x = y | 3 | 3", "x = y | 3");
test("x = 3 | y | 3", "x = y | 3");
test("x = y ^ 1 ^ 1", "x = y ^ 0");
test("x = y ^ 1 ^ 2", "x = y ^ 3");
test("x = y ^ 3 ^ 1", "x = y ^ 2");
test("x = 3 ^ y ^ 1", "x = y ^ 2");
test("x = y ^ 3 ^ 3", "x = y ^ 0");
test("x = 3 ^ y ^ 3", "x = y ^ 0");
test("x = Infinity | NaN", "x=0");
test("x = 12 | NaN", "x=12");
}
#[test]
fn test_fold_bitwise_op_with_big_int() {
test("x = 1n & 1n", "x = 1n");
test("x = 1n & 2n", "x = 0n");
test("x = 3n & 1n", "x = 1n");
test("x = 3n & 3n", "x = 3n");
test("x = 1n | 1n", "x = 1n");
test("x = 1n | 2n", "x = 3n");
test("x = 1n | 3n", "x = 3n");
test("x = 3n | 1n", "x = 3n");
test("x = 3n | 3n", "x = 3n");
test("x = 1n | 4n", "x = 5n");
test("x = 1n ^ 1n", "x = 0n");
test("x = 1n ^ 2n", "x = 3n");
test("x = 3n ^ 1n", "x = 2n");
test("x = 3n ^ 3n", "x = 0n");
test("x = -1n & 0n", "x = 0n");
test("x = 0n & -1n", "x = 0n");
test("x = 1n & 4n", "x = 0n");
test("x = 2n & 3n", "x = 2n");
test("x = 1n & 3000000000n", "x = 0n");
test("x = 3000000000n & 1n", "x = 0n");
// bitwise OR does not affect the sign of a bigint
test("x = 1n | 3000000001n", "x = 3000000001n");
test("x = 4294967295n | 0n", "x = 4294967295n");
test("x = y & 1n & 1n", "x = y & 1n");
test("x = y & 1n & 2n", "x = y & 0n");
test("x = y & 3n & 1n", "x = y & 1n");
test("x = 3n & y & 1n", "x = y & 1n");
test("x = y & 3n & 3n", "x = y & 3n");
test("x = 3n & y & 3n", "x = y & 3n");
test("x = y | 1n | 1n", "x = y | 1n");
test("x = y | 1n | 2n", "x = y | 3n");
test("x = y | 3n | 1n", "x = y | 3n");
test("x = 3n | y | 1n", "x = y | 3n");
test("x = y | 3n | 3n", "x = y | 3n");
test("x = 3n | y | 3n", "x = y | 3n");
test("x = y ^ 1n ^ 1n", "x = y ^ 0n");
test("x = y ^ 1n ^ 2n", "x = y ^ 3n");
test("x = y ^ 3n ^ 1n", "x = y ^ 2n");
test("x = 3n ^ y ^ 1n", "x = y ^ 2n");
test("x = y ^ 3n ^ 3n", "x = y ^ 0n");
test("x = 3n ^ y ^ 3n", "x = y ^ 0n");
// TypeError: Cannot mix BigInt and other types
test_same("1n & 1");
test_same("1n | 1");
test_same("1n ^ 1");
}
#[test]
fn test_fold_bitwise_op_additional() {
test("x = null & 1", "x = 0");
test("x = (2 ** 31 - 1) | 1", "x = 2147483647");
test("x = (2 ** 31) | 1", "x = -2147483647");
// https://github.com/oxc-project/oxc/issues/7944
test_same("(x - 1) & 1");
test_same("(y >> 3) & 7");
test("(y & 3) & 7", "y & 3");
test_same("(y | 3) & 7");
test("y | 3 & 7", "y | 3");
}
#[test]
fn test_fold_bit_shift() {
test("x = 1 << 0", "x=1");
test("x = -1 << 0", "x=-1");
test("x = 1 << 1", "x=2");
test("x = 3 << 1", "x=6");
test("x = 1 << 8", "x=256");
test("x = 1 >> 0", "x=1");
test("x = -1 >> 0", "x=-1");
test("x = 1 >> 1", "x=0");
test("x = 2 >> 1", "x=1");
test("x = 5 >> 1", "x=2");
test("x = 127 >> 3", "x=15");
test("x = 3 >> 1", "x=1");
test("x = 3 >> 2", "x=0");
test("x = 10 >> 1", "x=5");
test("x = 10 >> 2", "x=2");
test("x = 10 >> 5", "x=0");
test("x = 10 >>> 1", "x=5");
test("x = 10 >>> 2", "x=2");
test("x = 10 >>> 5", "x=0");
test("x = -1 >>> 1", "x=2147483647"); // 0x7fffffff
test("x = -1 >>> 0", "x=4294967295"); // 0xffffffff
test("x = -2 >>> 0", "x=4294967294"); // 0xfffffffe
test("x = 0x90000000 >>> 28", "x=9");
test("x = 0xffffffff << 0", "x=-1");
test("x = 0xffffffff << 4", "x=-16");
test("1 << 32", "1<<32");
test("1 << -1", "1<<-1");
test("1 >> 32", "1>>32");
// Regression on #6161, ported from <https://github.com/tc39/test262/blob/05c45a4c430ab6fee3e0c7f0d47d8a30d8876a6d/test/language/expressions/unsigned-right-shift/S9.6_A2.2.js>.
test("-2147483647 >>> 0", "2147483649");
test("-2147483648 >>> 0", "2147483648");
test("-2147483649 >>> 0", "2147483647");
test("-4294967295 >>> 0", "1");
test("-4294967296 >>> 0", "0");
test("-4294967297 >>> 0", "4294967295");
test("4294967295 >>> 0", "4294967295");
test("4294967296 >>> 0", "0");
test("4294967297 >>> 0", "1");
test("8589934591 >>> 0", "4294967295");
test("8589934592 >>> 0", "0");
test("8589934593 >>> 0", "1");
}
#[test]
fn test_fold_arithmetic() {
test("x = 10 + 20", "x = 30");
test("x = 2 / 4", "x = 0.5");
test("x = 2.25 * 3", "x = 6.75");
test_same("z = x * y");
test_same("x = y * 5");
test("x = 1 / 0", "x = Infinity");
test("x = 3 % 2", "x = 1");
test("x = 3 % -2", "x = 1");
test("x = -1 % 3", "x = -1");
test("x = 1 % 0", "x = NaN");
test("x = 2 ** 3", "x = 8");
test("x = 2 ** -3", "x = 0.125");
// FIXME
// test_same("x = 2 ** 55"); // backs off folding because 2 ** 55 is too large
// test_same("x = 3 ** -1"); // backs off because 3**-1 is shorter than 0.3333333333333333
test("x = 0 / 0", "x = NaN");
test("x = 0 % 0", "x = NaN");
test("x = (-1) ** 0.5", "x = NaN");
test_nospace("1n+ +1n", "1n + +1n");
test_nospace("1n- -1n", "1n - -1n");
test_nospace("a- -b", "a - -b");
}
#[test]
fn test_fold_arithmetic2() {
test_same("x = y + 10 + 20");
test_same("x = y / 2 / 4");
// test("x = y * 2.25 * 3", "x = y * 6.75");
test_same("x = y * 2.25 * z * 3");
test_same("z = x * y");
test_same("x = y * 5");
// test("x = y + (z * 24 * 60 * 60 * 1000)", "x = y + z * 864E5");
test("x = y + (z & 24 & 60 & 60 & 1000)", "x = y + (z & 8)");
}
#[test]
fn test_fold_arithmetic3() {
test("x = null * undefined", "x = NaN");
test("x = null * 1", "x = 0");
test("x = (null - 1) * 2", "x = -2");
test("x = (null + 1) * 2", "x = 2");
test("x = null ** 0", "x = 1");
test("x = (-0) ** 3", "x = -0");
test("x = 1 + null", "x = 1");
test("x = null + 1", "x = 1");
}
#[test]
fn test_fold_arithmetic_infinity() {
test("x=-Infinity-2", "x=-Infinity");
test("x=Infinity-2", "x=Infinity");
test("x=Infinity*5", "x=Infinity");
test("x = Infinity ** 2", "x = Infinity");
test("x = Infinity ** -2", "x = 0");
test("x = Infinity / Infinity", "x = NaN");
test("x = Infinity % Infinity", "x = NaN");
test("x = Infinity / 0", "x = Infinity");
test("x = Infinity % 0", "x = NaN");
}
#[test]
fn test_fold_left() {
test_same("(+x - 1) + 2"); // not yet
test("(+x & 1) & 2", "+x & 0");
}
#[test]
fn test_fold_left_child_op() {
test_same("x & infinity & 2"); // FIXME: want x & 0
test_same("x - infinity - 2"); // FIXME: want "x-infinity"
test_same("x - 1 + infinity");
test_same("x - 2 + 1");
test_same("x - 2 + 3");
test_same("1 + x - 2 + 1");
test_same("1 + x - 2 + 3");
test_same("1 + x - 2 + 3 - 1");
test_same("f(x)-0");
test_same("x-0-0"); // FIXME: want x - 0
test_same("x+2-2+2");
test_same("x+2-2+2-2");
test_same("x-2+2");
test_same("x-2+2-2");
test_same("x-2+2-2+2");
test_same("1+x-0-na_n");
test_same("1+f(x)-0-na_n");
test_same("1+x-0+na_n");
test_same("1+f(x)-0+na_n");
test_same("1+x+na_n"); // unfoldable
test_same("x+2-2"); // unfoldable
test_same("x+2"); // nothing to do
test_same("x-2"); // nothing to do
}
#[test]
fn test_associative_fold_constants_with_variables() {
// mul and add should not fold
test_same("alert(x * 12 * 20);");
test_same("alert(12 * x * 20);");
test_same("alert(x + 12 + 20);");
test_same("alert(12 + x + 20);");
test("alert(x & 12 & 20);", "alert(x & 4);");
test("alert(12 & x & 20);", "alert(x & 4);");
}
#[test]
fn test_to_number() {
test("x = +''", "x = 0");
test("x = +'+Infinity'", "x = Infinity");
test("x = +'-Infinity'", "x = -Infinity");
for op in ["", "+", "-"] {
for s in ["inf", "infinity", "INFINITY", "InFiNiTy"] {
test(&format!("x = +'{op}{s}'"), "x = NaN");
}
}
}
}
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