From 14d0590b0b339f4db4ab025ec3f054cf7fcf9a0e Mon Sep 17 00:00:00 2001
From: camc314 <18101008+camc314@users.noreply.github.com>
Date: Sun, 13 Oct 2024 06:26:31 +0000
Subject: [PATCH] feat(minifier): implement folding of simple function calls
 (`Boolean`) (#6484)

Basically `Boolean(true)` -> `true` or `Boolean(foo)` -> `!!foo`
---
 .../peephole_substitute_alternate_syntax.rs   | 27 ++++++++++++++++---
 tasks/minsize/minsize.snap                    |  6 ++---
 2 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/crates/oxc_minifier/src/ast_passes/peephole_substitute_alternate_syntax.rs b/crates/oxc_minifier/src/ast_passes/peephole_substitute_alternate_syntax.rs
index 18c6c2e35efba..422bd65296fed 100644
--- a/crates/oxc_minifier/src/ast_passes/peephole_substitute_alternate_syntax.rs
+++ b/crates/oxc_minifier/src/ast_passes/peephole_substitute_alternate_syntax.rs
@@ -466,8 +466,30 @@ impl<'a> PeepholeSubstituteAlternateSyntax {
             return None;
         }
         if call_expr.callee.is_global_reference_name("Boolean", ctx.symbols()) {
-            // TODO
-            None
+            // `Boolean(a)` -> `!!(a)`
+            // http://www.ecma-international.org/ecma-262/6.0/index.html#sec-boolean-constructor-boolean-value
+            // and
+            // http://www.ecma-international.org/ecma-262/6.0/index.html#sec-logical-not-operator-runtime-semantics-evaluation
+
+            let arg = call_expr.arguments.get_mut(0).and_then(|arg| arg.as_expression_mut())?;
+
+            if let Expression::UnaryExpression(unary_expr) = arg {
+                if unary_expr.operator == UnaryOperator::LogicalNot {
+                    return Some(ctx.ast.move_expression(arg));
+                }
+            }
+
+            Some(ctx.ast.expression_from_unary(ctx.ast.unary_expression(
+                call_expr.span,
+                UnaryOperator::LogicalNot,
+                ctx.ast.expression_from_unary(ctx.ast.unary_expression(
+                    call_expr.span,
+                    UnaryOperator::LogicalNot,
+                    ctx.ast.move_expression(
+                        call_expr.arguments.get_mut(0).and_then(|arg| arg.as_expression_mut())?,
+                    ),
+                )),
+            )))
         } else if call_expr.callee.is_global_reference_name("String", ctx.symbols()) {
             // `String(a)` -> `'' + (a)`
             let arg = call_expr.arguments.get_mut(0).and_then(|arg| arg.as_expression_mut())?;
@@ -881,7 +903,6 @@ mod test {
     }
 
     #[test]
-    #[ignore]
     fn test_simple_function_call2() {
         test("var a = Boolean(true)", "var a = !0");
         // Don't fold the existence check to preserve behavior
diff --git a/tasks/minsize/minsize.snap b/tasks/minsize/minsize.snap
index 66e16e5f5fe4c..635e557b4dacc 100644
--- a/tasks/minsize/minsize.snap
+++ b/tasks/minsize/minsize.snap
@@ -12,15 +12,15 @@ Original   | Minified   | esbuild    | Gzip       | esbuild
 
 555.77 kB  | 278.22 kB  | 270.13 kB  | 91.36 kB   | 90.80 kB   | d3.js     
 
-1.01 MB    | 470.08 kB  | 458.89 kB  | 126.96 kB  | 126.71 kB  | bundle.min.js
+1.01 MB    | 470.07 kB  | 458.89 kB  | 126.95 kB  | 126.71 kB  | bundle.min.js
 
 1.25 MB    | 670.94 kB  | 646.76 kB  | 164.72 kB  | 163.73 kB  | three.js  
 
-2.14 MB    | 756.32 kB  | 724.14 kB  | 182.74 kB  | 181.07 kB  | victory.js
+2.14 MB    | 756.31 kB  | 724.14 kB  | 182.74 kB  | 181.07 kB  | victory.js
 
 3.20 MB    | 1.05 MB    | 1.01 MB    | 334.08 kB  | 331.56 kB  | echarts.js
 
-6.69 MB    | 2.44 MB    | 2.31 MB    | 498.88 kB  | 488.28 kB  | antd.js   
+6.69 MB    | 2.44 MB    | 2.31 MB    | 498.86 kB  | 488.28 kB  | antd.js   
 
 10.95 MB   | 3.59 MB    | 3.49 MB    | 913.91 kB  | 915.50 kB  | typescript.js