feat(minifier): replace Math.pow with ** (#8730)

Replaces `Math.pow(a, b)` with `(+a) ** (+b)`. `+` does `ToNumber` and `**` does `Number::exponentiate` when both operands are number.
`+` is not added when `a` or `b` is already a number.

**Reference**
- [Spec of `Math.pow`](https://tc39.es/ecma262/multipage/numbers-and-dates.html#sec-math.pow)
- [Spec of `**`](https://tc39.es/ecma262/multipage/ecmascript-language-expressions.html#sec-exp-operator-runtime-semantics-evaluation)
- [Spec of unary `+`](https://tc39.es/ecma262/multipage/ecmascript-language-expressions.html#sec-unary-plus-operator-runtime-semantics-evaluation)

crates/oxc_minifier/src/peephole/replace_known_methods.rs

@@ -4,8 +4,8 @@ use cow_utils::CowUtils;
 
 use oxc_ast::ast::*;
 use oxc_ecmascript::{
-    constant_evaluation::ConstantEvaluation, StringCharAt, StringCharCodeAt, StringIndexOf,
-    StringLastIndexOf, StringSubstring, ToInt32,
+    constant_evaluation::{ConstantEvaluation, ValueType},
+    StringCharAt, StringCharCodeAt, StringIndexOf, StringLastIndexOf, StringSubstring, ToInt32,
 };
 use oxc_span::SPAN;
 use oxc_syntax::es_target::ESTarget;
@@ -63,6 +63,7 @@ impl<'a> PeepholeOptimizations {
             }
             "fromCharCode" => Self::try_fold_string_from_char_code(*span, arguments, object, ctx),
             "toString" => Self::try_fold_to_string(*span, arguments, object, ctx),
+            "pow" => self.try_fold_pow(*span, arguments, object, ctx),
             _ => None,
         };
         if let Some(replacement) = replacement {
@@ -342,6 +343,51 @@ impl<'a> PeepholeOptimizations {
         result.into_iter().rev().collect()
     }
 
+    /// `Math.pow(a, b)` -> `+(a) ** +b`
+    fn try_fold_pow(
+        &self,
+        span: Span,
+        arguments: &mut Arguments<'a>,
+        object: &Expression<'a>,
+        ctx: Ctx<'a, '_>,
+    ) -> Option<Expression<'a>> {
+        if self.target < ESTarget::ES2016 {
+            return None;
+        }
+
+        let Expression::Identifier(ident) = object else { return None };
+        if ident.name != "Math" || !ctx.is_global_reference(ident) {
+            return None;
+        }
+        if arguments.len() != 2 || arguments.iter().any(|arg| !arg.is_expression()) {
+            return None;
+        }
+
+        let mut second_arg = arguments.pop().expect("checked len above");
+        let second_arg = second_arg.to_expression_mut(); // checked above
+        let mut first_arg = arguments.pop().expect("checked len above");
+        let first_arg = first_arg.to_expression_mut(); // checked above
+
+        let wrap_with_unary_plus_if_needed = |expr: &mut Expression<'a>| {
+            if ValueType::from(&*expr).is_number() {
+                ctx.ast.move_expression(expr)
+            } else {
+                ctx.ast.expression_unary(
+                    SPAN,
+                    UnaryOperator::UnaryPlus,
+                    ctx.ast.move_expression(expr),
+                )
+            }
+        };
+
+        Some(ctx.ast.expression_binary(
+            span,
+            wrap_with_unary_plus_if_needed(first_arg),
+            BinaryOperator::Exponential,
+            wrap_with_unary_plus_if_needed(second_arg),
+        ))
+    }
+
     /// `[].concat(a).concat(b)` -> `[].concat(a, b)`
     /// `"".concat(a).concat(b)` -> `"".concat(a, b)`
     fn try_fold_concat_chain(&mut self, node: &mut Expression<'a>, ctx: Ctx<'a, '_>) {
@@ -1470,6 +1516,23 @@ mod test {
         test("/./.toString(b)", "/./.toString(b)");
     }
 
+    #[test]
+    fn test_fold_pow() {
+        test("Math.pow(2, 3)", "2 ** 3");
+        test("Math.pow(a, 3)", "+(a) ** 3");
+        test("Math.pow(2, b)", "2 ** +b");
+        test("Math.pow(a, b)", "+(a) ** +b");
+        test("Math.pow(2n, 3n)", "+(2n) ** +3n"); // errors both before and after
+        test("Math.pow(a + b, c)", "+(a + b) ** +c");
+        test_same("Math.pow()");
+        test_same("Math.pow(1)");
+        test_same("Math.pow(...a, 1)");
+        test_same("Math.pow(1, ...a)");
+        test_same("Math.pow(1, 2, 3)");
+        test_es2015("Math.pow(2, 3)", "Math.pow(2, 3)");
+        test_same("Unknown.pow(1, 2)");
+    }
+
     #[test]
     fn test_number_constants() {
         test("v = Number.POSITIVE_INFINITY", "v = Infinity");

tasks/minsize/minsize.snap

@@ -3,7 +3,7 @@ Original   | minified   | minified   | gzip       | gzip       | Fixture
 -------------------------------------------------------------------------------------
 72.14 kB   | 23.61 kB   | 23.70 kB   | 8.55 kB    | 8.54 kB    | react.development.js
 
-173.90 kB  | 59.71 kB   | 59.82 kB   | 19.26 kB   | 19.33 kB   | moment.js 
+173.90 kB  | 59.70 kB   | 59.82 kB   | 19.26 kB   | 19.33 kB   | moment.js 
 
 287.63 kB  | 89.58 kB   | 90.07 kB   | 31.08 kB   | 31.95 kB   | jquery.js 
 
@@ -11,17 +11,17 @@ Original   | minified   | minified   | gzip       | gzip       | Fixture
 
 544.10 kB  | 71.50 kB   | 72.48 kB   | 25.92 kB   | 26.20 kB   | lodash.js 
 
-555.77 kB  | 272.35 kB  | 270.13 kB  | 88.60 kB   | 90.80 kB   | d3.js     
+555.77 kB  | 272.12 kB  | 270.13 kB  | 88.59 kB   | 90.80 kB   | d3.js     
 
 1.01 MB    | 458.28 kB  | 458.89 kB  | 123.94 kB  | 126.71 kB  | bundle.min.js
 
-1.25 MB    | 650.82 kB  | 646.76 kB  | 161.51 kB  | 163.73 kB  | three.js  
+1.25 MB    | 650.70 kB  | 646.76 kB  | 161.49 kB  | 163.73 kB  | three.js  
 
-2.14 MB    | 719.54 kB  | 724.14 kB  | 162.47 kB  | 181.07 kB  | victory.js
+2.14 MB    | 719.06 kB  | 724.14 kB  | 162.43 kB  | 181.07 kB  | victory.js
 
-3.20 MB    | 1.01 MB    | 1.01 MB    | 325.41 kB  | 331.56 kB  | echarts.js
+3.20 MB    | 1.01 MB    | 1.01 MB    | 325.38 kB  | 331.56 kB  | echarts.js
 
 6.69 MB    | 2.30 MB    | 2.31 MB    | 470.00 kB  | 488.28 kB  | antd.js   
 
-10.95 MB   | 3.37 MB    | 3.49 MB    | 866.65 kB  | 915.50 kB  | typescript.js
+10.95 MB   | 3.37 MB    | 3.49 MB    | 866.66 kB  | 915.50 kB  | typescript.js