feat(minifier): store symbol information for for init variables

crates/oxc_minifier/src/ctx.rs

@@ -54,7 +54,7 @@ impl<'a> oxc_ecmascript::GlobalContext<'a> for Ctx<'a, '_> {
             .get_reference(reference_id)
             .symbol_id()
             .and_then(|symbol_id| self.state.symbol_values.get_symbol_value(symbol_id))
-            .filter(|sv| sv.write_references_count == 0 && !sv.for_statement_init)
+            .filter(|sv| sv.write_references_count == 0)
             .and_then(|sv| sv.initialized_constant.as_ref())
             .cloned()
     }
@@ -182,10 +182,6 @@ impl<'a> Ctx<'a, '_> {
             }
         }
 
-        let for_statement_init = self.ancestors().nth(1).is_some_and(|ancestor| {
-            ancestor.is_parent_of_for_statement_init() || ancestor.is_parent_of_for_statement_left()
-        });
-
         let mut read_references_count = 0;
         let mut write_references_count = 0;
         for r in self.scoping().get_resolved_references(symbol_id) {
@@ -201,7 +197,6 @@ impl<'a> Ctx<'a, '_> {
         let symbol_value = SymbolValue {
             initialized_constant: constant,
             exported,
-            for_statement_init,
             read_references_count,
             write_references_count,
             scope_id,

crates/oxc_minifier/src/peephole/inline.rs

@@ -10,15 +10,22 @@ impl<'a> PeepholeOptimizations {
     pub fn init_symbol_value(decl: &VariableDeclarator<'a>, ctx: &mut Ctx<'a, '_>) {
         let BindingPatternKind::BindingIdentifier(ident) = &decl.id.kind else { return };
         let Some(symbol_id) = ident.symbol_id.get() else { return };
-        let value = if decl.kind.is_var() {
-            // Skip constant value inlining for `var` declarations, due to TDZ problems.
+        let value = if decl.kind.is_var() || Self::is_for_statement_init(ctx) {
+            // - Skip constant value inlining for `var` declarations, due to TDZ problems.
+            // - Set None for for statement initializers as the value of these are set by the for statement.
             None
         } else {
             decl.init.as_ref().map_or(Some(ConstantValue::Undefined), |e| e.evaluate_value(ctx))
         };
         ctx.init_value(symbol_id, value);
     }
 
+    fn is_for_statement_init(ctx: &Ctx<'a, '_>) -> bool {
+        ctx.ancestors().nth(1).is_some_and(|ancestor| {
+            ancestor.is_parent_of_for_statement_init() || ancestor.is_parent_of_for_statement_left()
+        })
+    }
+
     pub fn inline_identifier_reference(expr: &mut Expression<'a>, ctx: &mut Ctx<'a, '_>) {
         let Expression::Identifier(ident) = expr else { return };
         let reference_id = ident.reference_id();
@@ -30,9 +37,6 @@ impl<'a> PeepholeOptimizations {
         if symbol_value.write_references_count > 0 {
             return;
         }
-        if symbol_value.for_statement_init {
-            return;
-        }
         let Some(cv) = &symbol_value.initialized_constant else { return };
         if symbol_value.read_references_count == 1
             || match cv {

crates/oxc_minifier/src/peephole/remove_unused_expression.rs

@@ -642,9 +642,6 @@ impl<'a> PeepholeOptimizations {
         if symbol_value.read_references_count > 0 {
             return false;
         }
-        if symbol_value.for_statement_init {
-            return false;
-        }
         *e = assign_expr.right.take_in(ctx.ast);
         ctx.state.changed = true;
         false
@@ -1079,7 +1076,9 @@ mod test {
         test_same_options("function foo(t) { return t = x(); } foo();", &options);
 
         // For loops
+        test_options("for (let i;;) i = 0", "for (let i;;);", &options);
         test_same_options("for (let i;;) foo(i)", &options);
+        test_same_options("for (let i;;) i = 0, foo(i)", &options);
         test_same_options("for (let i in []) foo(i)", &options);
         test_same_options("for (let element of list) element && (element.foo = bar)", &options);
         test_same_options("for (let key in obj) key && (obj[key] = bar)", &options);

crates/oxc_minifier/src/symbol_value.rs

@@ -12,9 +12,6 @@ pub struct SymbolValue<'a> {
     /// Symbol is exported.
     pub exported: bool,
 
-    /// Inside for statement initializer.
-    pub for_statement_init: bool,
-
     pub read_references_count: u32,
     pub write_references_count: u32,
 

tasks/minsize/minsize.snap

@@ -21,7 +21,7 @@ Original   | minified   | minified   | gzip       | gzip       | Iterations | Fi
 
 3.20 MB    | 1.00 MB    | 1.01 MB    | 323.12 kB  | 331.56 kB  |          3 | echarts.js 
 
-6.69 MB    | 2.22 MB    | 2.31 MB    | 459.29 kB  | 488.28 kB  |          4 | antd.js    
+6.69 MB    | 2.22 MB    | 2.31 MB    | 459.28 kB  | 488.28 kB  |          4 | antd.js    
 
-10.95 MB   | 3.34 MB    | 3.49 MB    | 855.39 kB  | 915.50 kB  |          4 | typescript.js 
+10.95 MB   | 3.34 MB    | 3.49 MB    | 855.34 kB  | 915.50 kB  |          4 | typescript.js 
 

tasks/track_memory_allocations/allocs_minifier.snap

@@ -4,5 +4,5 @@ RadixUIAdoptionSection.jsx | 2.52 kB        ||             75 |              4 |
 
 pdf.mjs                    | 567.30 kB      ||          19577 |           2898 ||          47403 |           7782 | 1.624 MB      
 
-antd.js                    | 6.69 MB        ||          99857 |          13518 ||         331724 |          70354 | 17.408 MB     
+antd.js                    | 6.69 MB        ||          99856 |          13518 ||         331725 |          70354 | 17.408 MB