feat(minifier): loop compressor passes (#6013)

crates/oxc_minifier/examples/minifier.rs

@@ -27,8 +27,9 @@ fn main() -> std::io::Result<()> {
     println!("{printed}");
 
     if twice {
-        let printed = minify(&printed, source_type, mangle);
-        println!("{printed}");
+        let printed2 = minify(&printed, source_type, mangle);
+        println!("{printed2}");
+        println!("same = {}", printed == printed2);
     }
 
     Ok(())

crates/oxc_minifier/src/ast_passes/collapse_variable_declarations.rs

@@ -9,25 +9,37 @@ use crate::{CompressOptions, CompressorPass};
 /// `var a; var b = 1; var c = 2` => `var a, b = 1; c = 2`
 pub struct CollapseVariableDeclarations {
     options: CompressOptions,
+
+    changed: bool,
 }
 
-impl<'a> CompressorPass<'a> for CollapseVariableDeclarations {}
+impl<'a> CompressorPass<'a> for CollapseVariableDeclarations {
+    fn changed(&self) -> bool {
+        self.changed
+    }
+
+    fn build(&mut self, program: &mut Program<'a>, ctx: &mut TraverseCtx<'a>) {
+        self.changed = false;
+        oxc_traverse::walk_program(self, program, ctx);
+    }
+}
 
 impl<'a> Traverse<'a> for CollapseVariableDeclarations {
     fn enter_statements(&mut self, stmts: &mut Vec<'a, Statement<'a>>, ctx: &mut TraverseCtx<'a>) {
-        if self.options.join_vars {
-            self.join_vars(stmts, ctx);
-        }
+        self.join_vars(stmts, ctx);
     }
 }
 
 impl<'a> CollapseVariableDeclarations {
     pub fn new(options: CompressOptions) -> Self {
-        Self { options }
+        Self { options, changed: false }
     }
 
     /// Join consecutive var statements
-    fn join_vars(&self, stmts: &mut Vec<'a, Statement<'a>>, ctx: &mut TraverseCtx<'a>) {
+    fn join_vars(&mut self, stmts: &mut Vec<'a, Statement<'a>>, ctx: &mut TraverseCtx<'a>) {
+        if self.options.join_vars {
+            return;
+        }
         // Collect all the consecutive ranges that contain joinable vars.
         // This is required because Rust prevents in-place vec mutation.
         let mut ranges = vec![];
@@ -83,6 +95,7 @@ impl<'a> CollapseVariableDeclarations {
             }
         }
         *stmts = new_stmts;
+        self.changed = true;
     }
 }
 

crates/oxc_minifier/src/ast_passes/exploit_assigns.rs

@@ -1,19 +1,31 @@
-use oxc_traverse::Traverse;
+use oxc_ast::ast::*;
+use oxc_traverse::{Traverse, TraverseCtx};
 
 use crate::CompressorPass;
 
 /// Tries to chain assignments together.
 ///
 /// <https://github.com/google/closure-compiler/blob/master/src/com/google/javascript/jscomp/ExploitAssigns.java>
-pub struct ExploitAssigns;
+pub struct ExploitAssigns {
+    changed: bool,
+}
 
-impl<'a> CompressorPass<'a> for ExploitAssigns {}
+impl<'a> CompressorPass<'a> for ExploitAssigns {
+    fn changed(&self) -> bool {
+        self.changed
+    }
+
+    fn build(&mut self, program: &mut Program<'a>, ctx: &mut TraverseCtx<'a>) {
+        self.changed = false;
+        oxc_traverse::walk_program(self, program, ctx);
+    }
+}
 
 impl<'a> Traverse<'a> for ExploitAssigns {}
 
 impl ExploitAssigns {
     pub fn new() -> Self {
-        Self {}
+        Self { changed: false }
     }
 }
 

crates/oxc_minifier/src/ast_passes/mod.rs

@@ -18,7 +18,7 @@ pub use statement_fusion::StatementFusion;
 
 use oxc_ast::ast::Program;
 use oxc_semantic::{ScopeTree, SymbolTable};
-use oxc_traverse::{walk_program, Traverse, TraverseCtx};
+use oxc_traverse::{Traverse, TraverseCtx};
 
 use crate::node_util::NodeUtil;
 
@@ -33,11 +33,7 @@ impl<'a> NodeUtil for TraverseCtx<'a> {
 }
 
 pub trait CompressorPass<'a>: Traverse<'a> {
-    fn build(&mut self, program: &mut Program<'a>, ctx: &mut TraverseCtx<'a>)
-    where
-        Self: Traverse<'a>,
-        Self: Sized,
-    {
-        walk_program(self, program, ctx);
-    }
+    fn changed(&self) -> bool;
+
+    fn build(&mut self, program: &mut Program<'a>, ctx: &mut TraverseCtx<'a>);
 }

crates/oxc_minifier/src/ast_passes/peephole_fold_constants.rs

@@ -22,10 +22,19 @@ use crate::{
 ///
 /// <https://github.com/google/closure-compiler/blob/master/src/com/google/javascript/jscomp/PeepholeFoldConstants.java>
 pub struct PeepholeFoldConstants {
-    evaluate: bool,
+    changed: bool,
 }
 
-impl<'a> CompressorPass<'a> for PeepholeFoldConstants {}
+impl<'a> CompressorPass<'a> for PeepholeFoldConstants {
+    fn changed(&self) -> bool {
+        self.changed
+    }
+
+    fn build(&mut self, program: &mut Program<'a>, ctx: &mut TraverseCtx<'a>) {
+        self.changed = false;
+        oxc_traverse::walk_program(self, program, ctx);
+    }
+}
 
 impl<'a> Traverse<'a> for PeepholeFoldConstants {
     fn exit_expression(&mut self, expr: &mut Expression<'a>, ctx: &mut TraverseCtx<'a>) {
@@ -35,17 +44,12 @@ impl<'a> Traverse<'a> for PeepholeFoldConstants {
 
 impl<'a> PeepholeFoldConstants {
     pub fn new() -> Self {
-        Self { evaluate: false }
-    }
-
-    pub fn with_evaluate(mut self, yes: bool) -> Self {
-        self.evaluate = yes;
-        self
+        Self { changed: false }
     }
 
     // [optimizeSubtree](https://github.com/google/closure-compiler/blob/75335a5138dde05030747abfd3c852cd34ea7429/src/com/google/javascript/jscomp/PeepholeFoldConstants.java#L72)
     // TODO: tryReduceOperandsForOp
-    pub fn fold_expression(&self, expr: &mut Expression<'a>, ctx: &mut TraverseCtx<'a>) {
+    pub fn fold_expression(&mut self, expr: &mut Expression<'a>, ctx: &mut TraverseCtx<'a>) {
         if let Some(folded_expr) = match expr {
             Expression::BinaryExpression(e) => self.try_fold_binary_operator(e, ctx),
             Expression::LogicalExpression(e)
@@ -60,6 +64,7 @@ impl<'a> PeepholeFoldConstants {
             _ => None,
         } {
             *expr = folded_expr;
+            self.changed = true;
         };
     }
 
@@ -92,13 +97,7 @@ impl<'a> PeepholeFoldConstants {
                 &binary_expr.right,
                 ctx,
             ),
-            // NOTE: string concat folding breaks our current evaluation of Test262 tests. The
-            // minifier is tested by comparing output of running the minifier once and twice,
-            // respectively. Since Test262Error messages include string concats, the outputs
-            // don't match (even though the produced code is valid). Additionally, We'll likely
-            // want to add `evaluate` checks for all constant folding, not just additions, but
-            // we're adding this here until a decision is made.
-            BinaryOperator::Addition if self.evaluate => {
+            BinaryOperator::Addition => {
                 self.try_fold_addition(binary_expr.span, &binary_expr.left, &binary_expr.right, ctx)
             }
             _ => None,

crates/oxc_minifier/src/ast_passes/peephole_minimize_conditions.rs

@@ -10,9 +10,20 @@ use crate::CompressorPass;
 /// with `? :` and short-circuit binary operators.
 ///
 /// <https://github.com/google/closure-compiler/blob/master/src/com/google/javascript/jscomp/PeepholeMinimizeConditions.java>
-pub struct PeepholeMinimizeConditions;
+pub struct PeepholeMinimizeConditions {
+    changed: bool,
+}
 
-impl<'a> CompressorPass<'a> for PeepholeMinimizeConditions {}
+impl<'a> CompressorPass<'a> for PeepholeMinimizeConditions {
+    fn changed(&self) -> bool {
+        self.changed
+    }
+
+    fn build(&mut self, program: &mut Program<'a>, ctx: &mut TraverseCtx<'a>) {
+        self.changed = false;
+        oxc_traverse::walk_program(self, program, ctx);
+    }
+}
 
 impl<'a> Traverse<'a> for PeepholeMinimizeConditions {
     fn exit_expression(&mut self, expr: &mut Expression<'a>, ctx: &mut TraverseCtx<'a>) {
@@ -21,13 +32,14 @@ impl<'a> Traverse<'a> for PeepholeMinimizeConditions {
             _ => None,
         } {
             *expr = folded_expr;
+            self.changed = true;
         };
     }
 }
 
 impl<'a> PeepholeMinimizeConditions {
     pub fn new() -> Self {
-        Self
+        Self { changed: false }
     }
 
     /// Try to minimize NOT nodes such as `!(x==y)`.

crates/oxc_minifier/src/ast_passes/peephole_remove_dead_code.rs

@@ -10,17 +10,30 @@ use crate::{keep_var::KeepVar, node_util::NodeUtil, tri::Tri, CompressorPass};
 /// Terser option: `dead_code: true`.
 ///
 /// See `KeepVar` at the end of this file for `var` hoisting logic.
-pub struct PeepholeRemoveDeadCode;
+pub struct PeepholeRemoveDeadCode {
+    changed: bool,
+}
 
-impl<'a> CompressorPass<'a> for PeepholeRemoveDeadCode {}
+impl<'a> CompressorPass<'a> for PeepholeRemoveDeadCode {
+    fn changed(&self) -> bool {
+        self.changed
+    }
+
+    fn build(&mut self, program: &mut Program<'a>, ctx: &mut TraverseCtx<'a>) {
+        self.changed = false;
+        oxc_traverse::walk_program(self, program, ctx);
+    }
+}
 
 impl<'a> Traverse<'a> for PeepholeRemoveDeadCode {
     fn enter_statement(&mut self, stmt: &mut Statement<'a>, ctx: &mut TraverseCtx<'a>) {
-        Self::fold_if_statement(stmt, ctx);
+        self.fold_if_statement(stmt, ctx);
     }
 
     fn exit_statements(&mut self, stmts: &mut Vec<'a, Statement<'a>>, ctx: &mut TraverseCtx<'a>) {
-        stmts.retain(|stmt| !matches!(stmt, Statement::EmptyStatement(_)));
+        if stmts.iter().any(|stmt| matches!(stmt, Statement::EmptyStatement(_))) {
+            stmts.retain(|stmt| !matches!(stmt, Statement::EmptyStatement(_)));
+        }
         self.dead_code_elimination(stmts, ctx);
     }
 
@@ -30,13 +43,14 @@ impl<'a> Traverse<'a> for PeepholeRemoveDeadCode {
             _ => None,
         } {
             *expr = folded_expr;
+            self.changed = true;
         }
     }
 }
 
 impl<'a> PeepholeRemoveDeadCode {
     pub fn new() -> Self {
-        Self {}
+        Self { changed: false }
     }
 
     /// Removes dead code thats comes after `return` statements after inlining `if` statements
@@ -76,6 +90,7 @@ impl<'a> PeepholeRemoveDeadCode {
         }
 
         let mut i = 0;
+        let len = stmts.len();
         stmts.retain(|s| {
             i += 1;
             if i - 1 <= index {
@@ -88,25 +103,35 @@ impl<'a> PeepholeRemoveDeadCode {
             false
         });
 
+        let all_hoisted = keep_var.all_hoisted();
         if let Some(stmt) = keep_var.get_variable_declaration_statement() {
             stmts.push(stmt);
+            if !all_hoisted {
+                self.changed = true;
+            }
+        }
+
+        if stmts.len() != len {
+            self.changed = true;
         }
     }
 
-    fn fold_if_statement(stmt: &mut Statement<'a>, ctx: &mut TraverseCtx<'a>) {
+    fn fold_if_statement(&mut self, stmt: &mut Statement<'a>, ctx: &mut TraverseCtx<'a>) {
         let Statement::IfStatement(if_stmt) = stmt else { return };
 
         // Descend and remove `else` blocks first.
         if let Some(alternate) = &mut if_stmt.alternate {
-            Self::fold_if_statement(alternate, ctx);
+            self.fold_if_statement(alternate, ctx);
             if matches!(alternate, Statement::EmptyStatement(_)) {
                 if_stmt.alternate = None;
+                self.changed = true;
             }
         }
 
         match ctx.get_boolean_value(&if_stmt.test) {
             Tri::True => {
                 *stmt = ctx.ast.move_statement(&mut if_stmt.consequent);
+                self.changed = true;
             }
             Tri::False => {
                 *stmt = if let Some(alternate) = &mut if_stmt.alternate {
@@ -119,6 +144,7 @@ impl<'a> PeepholeRemoveDeadCode {
                         .get_variable_declaration_statement()
                         .unwrap_or_else(|| ctx.ast.statement_empty(SPAN))
                 };
+                self.changed = true;
             }
             Tri::Unknown => {}
         }

crates/oxc_minifier/src/ast_passes/peephole_substitute_alternate_syntax.rs

@@ -14,9 +14,19 @@ use crate::{node_util::NodeUtil, CompressOptions, CompressorPass};
 pub struct PeepholeSubstituteAlternateSyntax {
     options: CompressOptions,
     in_define_export: bool,
+    changed: bool,
 }
 
-impl<'a> CompressorPass<'a> for PeepholeSubstituteAlternateSyntax {}
+impl<'a> CompressorPass<'a> for PeepholeSubstituteAlternateSyntax {
+    fn changed(&self) -> bool {
+        self.changed
+    }
+
+    fn build(&mut self, program: &mut Program<'a>, ctx: &mut TraverseCtx<'a>) {
+        self.changed = false;
+        oxc_traverse::walk_program(self, program, ctx);
+    }
+}
 
 impl<'a> Traverse<'a> for PeepholeSubstituteAlternateSyntax {
     fn enter_statement(&mut self, stmt: &mut Statement<'a>, _ctx: &mut TraverseCtx<'a>) {
@@ -30,7 +40,7 @@ impl<'a> Traverse<'a> for PeepholeSubstituteAlternateSyntax {
         _ctx: &mut TraverseCtx<'a>,
     ) {
         // We may fold `void 1` to `void 0`, so compress it after visiting
-        Self::compress_return_statement(stmt);
+        self.compress_return_statement(stmt);
     }
 
     fn enter_variable_declaration(
@@ -39,7 +49,7 @@ impl<'a> Traverse<'a> for PeepholeSubstituteAlternateSyntax {
         _ctx: &mut TraverseCtx<'a>,
     ) {
         for declarator in decl.declarations.iter_mut() {
-            Self::compress_variable_declarator(declarator);
+            self.compress_variable_declarator(declarator);
         }
     }
 
@@ -83,7 +93,7 @@ impl<'a> Traverse<'a> for PeepholeSubstituteAlternateSyntax {
 
 impl<'a> PeepholeSubstituteAlternateSyntax {
     pub fn new(options: CompressOptions) -> Self {
-        Self { options, in_define_export: false }
+        Self { options, in_define_export: false, changed: false }
     }
 
     /* Utilities */
@@ -120,14 +130,14 @@ impl<'a> PeepholeSubstituteAlternateSyntax {
 
     /// Remove block from single line blocks
     /// `{ block } -> block`
-    #[allow(clippy::only_used_in_recursion)] // `&self` is only used in recursion
-    fn compress_block(&self, stmt: &mut Statement<'a>) {
+    fn compress_block(&mut self, stmt: &mut Statement<'a>) {
         if let Statement::BlockStatement(block) = stmt {
             // Avoid compressing `if (x) { var x = 1 }` to `if (x) var x = 1` due to different
             // semantics according to AnnexB, which lead to different semantics.
             if block.body.len() == 1 && !block.body[0].is_declaration() {
                 *stmt = block.body.remove(0);
                 self.compress_block(stmt);
+                self.changed = true;
             }
         }
     }
@@ -230,18 +240,20 @@ impl<'a> PeepholeSubstituteAlternateSyntax {
     ///
     /// `return undefined` -> `return`
     /// `return void 0` -> `return`
-    fn compress_return_statement(stmt: &mut ReturnStatement<'a>) {
+    fn compress_return_statement(&mut self, stmt: &mut ReturnStatement<'a>) {
         if stmt.argument.as_ref().is_some_and(|expr| expr.is_undefined() || expr.is_void_0()) {
             stmt.argument = None;
+            self.changed = true;
         }
     }
 
-    fn compress_variable_declarator(decl: &mut VariableDeclarator<'a>) {
+    fn compress_variable_declarator(&mut self, decl: &mut VariableDeclarator<'a>) {
         if decl.kind.is_const() {
             return;
         }
         if decl.init.as_ref().is_some_and(|init| init.is_undefined() || init.is_void_0()) {
             decl.init = None;
+            self.changed = true;
         }
     }
 }

crates/oxc_minifier/src/ast_passes/remove_syntax.rs

@@ -13,7 +13,15 @@ pub struct RemoveSyntax {
     options: CompressOptions,
 }
 
-impl<'a> CompressorPass<'a> for RemoveSyntax {}
+impl<'a> CompressorPass<'a> for RemoveSyntax {
+    fn changed(&self) -> bool {
+        false
+    }
+
+    fn build(&mut self, program: &mut Program<'a>, ctx: &mut TraverseCtx<'a>) {
+        oxc_traverse::walk_program(self, program, ctx);
+    }
+}
 
 impl<'a> Traverse<'a> for RemoveSyntax {
     fn enter_statements(&mut self, stmts: &mut Vec<'a, Statement<'a>>, _ctx: &mut TraverseCtx<'a>) {

crates/oxc_minifier/src/ast_passes/statement_fusion.rs

@@ -10,32 +10,43 @@ use crate::CompressorPass;
 /// Tries to fuse all the statements in a block into a one statement by using COMMAs or statements.
 ///
 /// <https://github.com/google/closure-compiler/blob/master/src/com/google/javascript/jscomp/StatementFusion.java>
-pub struct StatementFusion;
+pub struct StatementFusion {
+    changed: bool,
+}
 
-impl<'a> CompressorPass<'a> for StatementFusion {}
+impl<'a> CompressorPass<'a> for StatementFusion {
+    fn changed(&self) -> bool {
+        self.changed
+    }
+
+    fn build(&mut self, program: &mut Program<'a>, ctx: &mut TraverseCtx<'a>) {
+        self.changed = false;
+        oxc_traverse::walk_program(self, program, ctx);
+    }
+}
 
 impl<'a> Traverse<'a> for StatementFusion {
     fn exit_program(&mut self, program: &mut Program<'a>, ctx: &mut TraverseCtx<'a>) {
-        Self::fuse_statements(&mut program.body, ctx);
+        self.fuse_statements(&mut program.body, ctx);
     }
 
     fn exit_function_body(&mut self, body: &mut FunctionBody<'a>, ctx: &mut TraverseCtx<'a>) {
-        Self::fuse_statements(&mut body.statements, ctx);
+        self.fuse_statements(&mut body.statements, ctx);
     }
 
     fn exit_block_statement(&mut self, block: &mut BlockStatement<'a>, ctx: &mut TraverseCtx<'a>) {
-        Self::fuse_statements(&mut block.body, ctx);
+        self.fuse_statements(&mut block.body, ctx);
     }
 }
 
 impl<'a> StatementFusion {
     pub fn new() -> Self {
-        Self {}
+        Self { changed: false }
     }
 
-    fn fuse_statements(stmts: &mut Vec<'a, Statement<'a>>, ctx: &mut TraverseCtx<'a>) {
+    fn fuse_statements(&mut self, stmts: &mut Vec<'a, Statement<'a>>, ctx: &mut TraverseCtx<'a>) {
         if Self::can_fuse_into_one_statement(stmts) {
-            Self::fuse_into_one_statement(stmts, ctx);
+            self.fuse_into_one_statement(stmts, ctx);
         }
     }
 
@@ -75,7 +86,11 @@ impl<'a> StatementFusion {
         }
     }
 
-    fn fuse_into_one_statement(stmts: &mut Vec<'a, Statement<'a>>, ctx: &mut TraverseCtx<'a>) {
+    fn fuse_into_one_statement(
+        &mut self,
+        stmts: &mut Vec<'a, Statement<'a>>,
+        ctx: &mut TraverseCtx<'a>,
+    ) {
         let len = stmts.len();
         let mut expressions = ctx.ast.vec();
 
@@ -103,6 +118,7 @@ impl<'a> StatementFusion {
         Self::fuse_expression_into_control_flow_statement(last, expressions, ctx);
 
         *stmts = ctx.ast.vec1(ctx.ast.move_statement(last));
+        self.changed = true;
     }
 
     fn fuse_expression_into_control_flow_statement(

crates/oxc_minifier/src/compressor.rs

@@ -35,69 +35,50 @@ impl<'a> Compressor<'a> {
         program: &mut Program<'a>,
     ) {
         let mut ctx = TraverseCtx::new(scopes, symbols, self.allocator);
-        self.remove_syntax(program, &mut ctx);
+        RemoveSyntax::new(self.options).build(program, &mut ctx);
 
         if self.options.dead_code_elimination {
             self.dead_code_elimination(program, &mut ctx);
             return;
         }
 
-        // earlyPeepholeOptimizations
-        // TODO: MinimizeExitPoints
-        self.minimize_conditions(program, &mut ctx);
-        self.substitute_alternate_syntax(program, &mut ctx);
-        // TODO: PeepholeReplaceKnownMethods
-        self.remove_dead_code(program, &mut ctx);
-        self.fold_constants(program, &mut ctx);
+        ExploitAssigns::new().build(program, &mut ctx);
+        CollapseVariableDeclarations::new(self.options).build(program, &mut ctx);
 
-        // latePeepholeOptimizations
-        // TODO: StatementFusion
-        self.remove_dead_code(program, &mut ctx);
-        self.minimize_conditions(program, &mut ctx);
-        self.substitute_alternate_syntax(program, &mut ctx);
-        // TODO: PeepholeReplaceKnownMethods
-        self.fold_constants(program, &mut ctx);
+        // See `latePeepholeOptimizations`
+        let mut passes: [&mut dyn CompressorPass; 5] = [
+            &mut StatementFusion::new(),
+            &mut PeepholeRemoveDeadCode::new(),
+            // TODO: MinimizeExitPoints
+            &mut PeepholeMinimizeConditions::new(),
+            &mut PeepholeSubstituteAlternateSyntax::new(self.options),
+            // TODO: PeepholeReplaceKnownMethods
+            &mut PeepholeFoldConstants::new(),
+        ];
 
-        self.exploit_assigns(program, &mut ctx);
-        self.collapse_variable_declarations(program, &mut ctx);
+        let mut i = 0;
+        loop {
+            let mut changed = false;
+            for pass in &mut passes {
+                pass.build(program, &mut ctx);
+                if pass.changed() {
+                    changed = true;
+                }
+            }
+            if !changed {
+                break;
+            }
+            if i > 50 {
+                debug_assert!(false, "Ran in a infinite loop.");
+                break;
+            }
+            i += 1;
+        }
     }
 
     fn dead_code_elimination(self, program: &mut Program<'a>, ctx: &mut TraverseCtx<'a>) {
-        self.fold_constants(program, ctx);
-        self.minimize_conditions(program, ctx);
-        self.remove_dead_code(program, ctx);
-    }
-
-    fn remove_syntax(&self, program: &mut Program<'a>, ctx: &mut TraverseCtx<'a>) {
-        RemoveSyntax::new(self.options).build(program, ctx);
-    }
-
-    fn minimize_conditions(&self, program: &mut Program<'a>, ctx: &mut TraverseCtx<'a>) {
+        PeepholeFoldConstants::new().build(program, ctx);
         PeepholeMinimizeConditions::new().build(program, ctx);
-    }
-
-    fn fold_constants(&self, program: &mut Program<'a>, ctx: &mut TraverseCtx<'a>) {
-        PeepholeFoldConstants::new().with_evaluate(self.options.evaluate).build(program, ctx);
-    }
-
-    fn substitute_alternate_syntax(&self, program: &mut Program<'a>, ctx: &mut TraverseCtx<'a>) {
-        PeepholeSubstituteAlternateSyntax::new(self.options).build(program, ctx);
-    }
-
-    fn remove_dead_code(&self, program: &mut Program<'a>, ctx: &mut TraverseCtx<'a>) {
         PeepholeRemoveDeadCode::new().build(program, ctx);
     }
-
-    #[allow(unused)]
-    fn statement_fusion(&self, program: &mut Program<'a>, ctx: &mut TraverseCtx<'a>) {
-        StatementFusion::new().build(program, ctx);
-    }
-
-    fn collapse_variable_declarations(&self, program: &mut Program<'a>, ctx: &mut TraverseCtx<'a>) {
-        CollapseVariableDeclarations::new(self.options).build(program, ctx);
-    }
-
-    fn exploit_assigns(&self, program: &mut Program<'a>, ctx: &mut TraverseCtx<'a>) {
-        ExploitAssigns::new().build(program, ctx);
-    }
 }

crates/oxc_minifier/src/keep_var.rs

@@ -4,6 +4,7 @@ use oxc_span::{Atom, Span, SPAN};
 pub struct KeepVar<'a> {
     ast: AstBuilder<'a>,
     vars: std::vec::Vec<(Atom<'a>, Span)>,
+    all_hoisted: bool,
 }
 
 impl<'a> Visit<'a> for KeepVar<'a> {
@@ -37,6 +38,9 @@ impl<'a> Visit<'a> for KeepVar<'a> {
                     decl.bound_names(&mut |ident| {
                         self.vars.push((ident.name.clone(), ident.span));
                     });
+                    if decl.has_init() {
+                        self.all_hoisted = false;
+                    }
                 }
             }
             _ => {}
@@ -46,7 +50,11 @@ impl<'a> Visit<'a> for KeepVar<'a> {
 
 impl<'a> KeepVar<'a> {
     pub fn new(ast: AstBuilder<'a>) -> Self {
-        Self { ast, vars: std::vec![] }
+        Self { ast, vars: std::vec![], all_hoisted: true }
+    }
+
+    pub fn all_hoisted(&self) -> bool {
+        self.all_hoisted
     }
 
     pub fn get_variable_declaration_statement(self) -> Option<Statement<'a>> {

tasks/minsize/minsize.snap

@@ -1,26 +1,26 @@
 Original   | Minified   | esbuild    | Gzip       | esbuild   
 
-72.14 kB   | 24.32 kB   | 23.70 kB   | 8.71 kB    | 8.54 kB    | react.development.js
+72.14 kB   | 24.47 kB   | 23.70 kB   | 8.65 kB    | 8.54 kB    | react.development.js
 
-173.90 kB  | 61.79 kB   | 59.82 kB   | 19.57 kB   | 19.33 kB   | moment.js 
+173.90 kB  | 61.71 kB   | 59.82 kB   | 19.56 kB   | 19.33 kB   | moment.js 
 
-287.63 kB  | 92.89 kB   | 90.07 kB   | 32.32 kB   | 31.95 kB   | jquery.js 
+287.63 kB  | 92.83 kB   | 90.07 kB   | 32.29 kB   | 31.95 kB   | jquery.js 
 
-342.15 kB  | 122.41 kB  | 118.14 kB  | 44.77 kB   | 44.37 kB   | vue.js    
+342.15 kB  | 124.14 kB  | 118.14 kB  | 44.81 kB   | 44.37 kB   | vue.js    
 
-544.10 kB  | 73.54 kB   | 72.48 kB   | 26.13 kB   | 26.20 kB   | lodash.js 
+544.10 kB  | 74.13 kB   | 72.48 kB   | 26.23 kB   | 26.20 kB   | lodash.js 
 
-555.77 kB  | 277.01 kB  | 270.13 kB  | 91.22 kB   | 90.80 kB   | d3.js     
+555.77 kB  | 278.71 kB  | 270.13 kB  | 91.40 kB   | 90.80 kB   | d3.js     
 
-1.01 MB    | 468.10 kB  | 458.89 kB  | 126.67 kB  | 126.71 kB  | bundle.min.js
+1.01 MB    | 470.11 kB  | 458.89 kB  | 126.97 kB  | 126.71 kB  | bundle.min.js
 
-1.25 MB    | 663.51 kB  | 646.76 kB  | 163.76 kB  | 163.73 kB  | three.js  
+1.25 MB    | 671.02 kB  | 646.76 kB  | 164.72 kB  | 163.73 kB  | three.js  
 
-2.14 MB    | 742.01 kB  | 724.14 kB  | 181.59 kB  | 181.07 kB  | victory.js
+2.14 MB    | 756.70 kB  | 724.14 kB  | 182.87 kB  | 181.07 kB  | victory.js
 
-3.20 MB    | 1.03 MB    | 1.01 MB    | 332.45 kB  | 331.56 kB  | echarts.js
+3.20 MB    | 1.05 MB    | 1.01 MB    | 334.11 kB  | 331.56 kB  | echarts.js
 
-6.69 MB    | 2.39 MB    | 2.31 MB    | 496.45 kB  | 488.28 kB  | antd.js   
+6.69 MB    | 2.44 MB    | 2.31 MB    | 498.90 kB  | 488.28 kB  | antd.js   
 
-10.95 MB   | 3.56 MB    | 3.49 MB    | 911.22 kB  | 915.50 kB  | typescript.js
+10.95 MB   | 3.59 MB    | 3.49 MB    | 913.91 kB  | 915.50 kB  | typescript.js