refactor(minifier): move equality comparison to ConstantEvaluation

Author: sapphi-red

crates/oxc_ecmascript/src/constant_evaluation/equality_comparison.rs

@@ -0,0 +1,130 @@
+use oxc_ast::ast::{Expression, NumberBase};
+
+use super::{ConstantEvaluation, ValueType};
+
+/// <https://tc39.es/ecma262/#sec-abstract-equality-comparison>
+pub(super) fn abstract_equality_comparison<'a>(
+    c: &impl ConstantEvaluation<'a>,
+    left_expr: &Expression<'a>,
+    right_expr: &Expression<'a>,
+) -> 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 strict_equality_comparison(c, left_expr, right_expr);
+        }
+        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)
+        {
+            if let Some(num) = c.get_side_free_number_value(right_expr) {
+                let number_literal_expr = c.ast().expression_numeric_literal(
+                    oxc_span::SPAN,
+                    num,
+                    None,
+                    if num.fract() == 0.0 { NumberBase::Decimal } else { NumberBase::Float },
+                );
+                return abstract_equality_comparison(c, left_expr, &number_literal_expr);
+            }
+            return None;
+        }
+
+        if matches!((left, right), (ValueType::String, ValueType::Number))
+            || matches!(left, ValueType::Boolean)
+        {
+            if let Some(num) = c.get_side_free_number_value(left_expr) {
+                let number_literal_expr = c.ast().expression_numeric_literal(
+                    oxc_span::SPAN,
+                    num,
+                    None,
+                    if num.fract() == 0.0 { NumberBase::Decimal } else { NumberBase::Float },
+                );
+                return abstract_equality_comparison(c, &number_literal_expr, right_expr);
+            }
+            return None;
+        }
+
+        if matches!(left, ValueType::BigInt) || matches!(right, ValueType::BigInt) {
+            let left_bigint = c.get_side_free_bigint_value(left_expr);
+            let right_bigint = c.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)]
+pub(super) fn strict_equality_comparison<'a>(
+    c: &impl ConstantEvaluation<'a>,
+    left_expr: &Expression<'a>,
+    right_expr: &Expression<'a>,
+) -> Option<bool> {
+    let left = ValueType::from(left_expr);
+    let right = ValueType::from(right_expr);
+    if !left.is_undetermined() && !right.is_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 lnum = c.get_side_free_number_value(left_expr)?;
+                let rnum = c.get_side_free_number_value(right_expr)?;
+                if lnum.is_nan() || rnum.is_nan() {
+                    return Some(false);
+                }
+                Some(lnum == rnum)
+            }
+            ValueType::String => {
+                let left = c.get_side_free_string_value(left_expr)?;
+                let right = c.get_side_free_string_value(right_expr)?;
+                Some(left == right)
+            }
+            ValueType::Undefined | ValueType::Null => Some(true),
+            ValueType::Boolean => {
+                let left = c.get_boolean_value(left_expr)?;
+                let right = c.get_boolean_value(right_expr)?;
+                Some(left == right)
+            }
+            ValueType::BigInt => {
+                let left = c.get_side_free_bigint_value(left_expr)?;
+                let right = c.get_side_free_bigint_value(right_expr)?;
+                Some(left == right)
+            }
+            ValueType::Object => None,
+            ValueType::Undetermined => unreachable!(),
+        };
+    }
+
+    // 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
+}

crates/oxc_ecmascript/src/constant_evaluation/mod.rs

@@ -3,10 +3,12 @@ use std::{borrow::Cow, cmp::Ordering};
 use num_bigint::BigInt;
 use num_traits::{ToPrimitive, Zero};
 
-use oxc_ast::ast::*;
+use equality_comparison::{abstract_equality_comparison, strict_equality_comparison};
+use oxc_ast::{ast::*, AstBuilder};
 
 use crate::{side_effects::MayHaveSideEffects, ToBigInt, ToBoolean, ToInt32, ToJsString, ToNumber};
 
+mod equality_comparison;
 mod is_literal_value;
 mod value;
 mod value_type;
@@ -15,6 +17,8 @@ pub use value::ConstantValue;
 pub use value_type::ValueType;
 
 pub trait ConstantEvaluation<'a>: MayHaveSideEffects {
+    fn ast(&self) -> AstBuilder<'a>;
+
     fn resolve_binding(&self, ident: &IdentifierReference<'a>) -> Option<ConstantValue<'a>> {
         match ident.name.as_str() {
             "undefined" if self.is_global_reference(ident) => Some(ConstantValue::Undefined),
@@ -374,7 +378,31 @@ pub trait ConstantEvaluation<'a>: MayHaveSideEffects {
                 }
                 None
             }
-            _ => None,
+            BinaryOperator::StrictEquality
+            | BinaryOperator::StrictInequality
+            | BinaryOperator::Equality
+            | BinaryOperator::Inequality => {
+                if self.expression_may_have_side_effects(left)
+                    || self.expression_may_have_side_effects(right)
+                {
+                    return None;
+                }
+                let value = match operator {
+                    BinaryOperator::StrictEquality | BinaryOperator::StrictInequality => {
+                        strict_equality_comparison(self, left, right)?
+                    }
+                    BinaryOperator::Equality | BinaryOperator::Inequality => {
+                        abstract_equality_comparison(self, left, right)?
+                    }
+                    _ => unreachable!(),
+                };
+                Some(ConstantValue::Boolean(match operator {
+                    BinaryOperator::StrictEquality | BinaryOperator::Equality => value,
+                    BinaryOperator::StrictInequality | BinaryOperator::Inequality => !value,
+                    _ => unreachable!(),
+                }))
+            }
+            BinaryOperator::In => None,
         }
     }
 

crates/oxc_minifier/src/ctx.rs

@@ -1,6 +1,6 @@
 use std::ops::Deref;
 
-use oxc_ast::ast::*;
+use oxc_ast::{ast::*, AstBuilder};
 use oxc_ecmascript::{
     constant_evaluation::{ConstantEvaluation, ConstantValue},
     side_effects::MayHaveSideEffects,
@@ -19,7 +19,11 @@ impl<'a, 'b> Deref for Ctx<'a, 'b> {
     }
 }
 
-impl<'a> ConstantEvaluation<'a> for Ctx<'a, '_> {}
+impl<'a> ConstantEvaluation<'a> for Ctx<'a, '_> {
+    fn ast(&self) -> AstBuilder<'a> {
+        self.ast
+    }
+}
 
 impl MayHaveSideEffects for Ctx<'_, '_> {
     fn is_global_reference(&self, ident: &IdentifierReference<'_>) -> bool {