fix(minifier): avoid unsafe return removal in labeled blocks (#25406)

revert #24813 currently there is no way to validate if stmt can be
removed if its inside a block

correct issue with incorrect removal of `return` stmt not at termination
points


```js
(function() {
  label: {
    console.log('before return');
    return;
  }
  console.log('unreachable!');
})();
```

ref: https://github.com/rolldown/rolldown/issues/10555

crates/oxc_minifier/src/peephole/minimize_statements.rs

@@ -374,9 +374,6 @@ impl<'a> PeepholeOptimizations {
             Statement::ForOfStatement(for_of_stmt) => {
                 Self::handle_for_of_statement(for_of_stmt, result, ctx);
             }
-            Statement::LabeledStatement(label_stmt) => {
-                Self::handle_labeled_statement(label_stmt, result, ctx);
-            }
             Statement::BlockStatement(block_stmt) => Self::handle_block(result, block_stmt, ctx),
             stmt => result.push(stmt),
         }
@@ -1238,33 +1235,6 @@ impl<'a> PeepholeOptimizations {
         result.push(Statement::ForOfStatement(for_of_stmt));
     }
 
-    fn handle_labeled_statement(
-        mut labeled_stmt: ArenaBox<'a, LabeledStatement<'a>>,
-        result: &mut ArenaVec<'a, Statement<'a>>,
-        ctx: &mut TraverseCtx<'a>,
-    ) {
-        if let Statement::BlockStatement(block_stmt) = &mut labeled_stmt.body {
-            Self::minimize_statements(&mut block_stmt.body, ctx);
-        } else if !Self::statement_cares_about_scope(&labeled_stmt.body) {
-            let mut stmts = ArenaVec::from_value_in(labeled_stmt.body.take_in(ctx), ctx);
-            Self::minimize_statements(&mut stmts, ctx);
-            labeled_stmt.body = match stmts.len() {
-                0 => Statement::new_empty_statement(labeled_stmt.body.span(), ctx),
-                1 => stmts[0].take_in(ctx),
-                _ => {
-                    ctx.notice_change();
-                    Statement::new_block_statement_with_scope_id(
-                        labeled_stmt.span,
-                        stmts,
-                        ctx.create_child_scope_of_current(ScopeFlags::empty()),
-                        ctx,
-                    )
-                }
-            };
-        }
-        result.push(Statement::LabeledStatement(labeled_stmt));
-    }
-
     /// `appendIfOrLabelBodyPreservingScope`: <https://github.com/evanw/esbuild/blob/v0.24.2/internal/js_parser/js_parser.go#L9839>
     fn handle_block(
         result: &mut ArenaVec<'a, Statement<'a>>,

crates/oxc_minifier/tests/peephole/minimize_exit_points.rs

@@ -25,6 +25,8 @@ fn test_break_optimization() {
     test("f:g:{if(a()){break f;}else{break f;} break f;}", "f:g:{if(a())break f;break f}"); // f:g:a();
     test("function f() { a: break a; }", "function f() {}");
     test("function f() { a: { break a; } }", "function f() {}");
+    test_same("function f() { a: { b(); break a; } c(); }");
+    test_same("function f() { a: { b(); return; } c(); }");
 }
 
 #[test]
@@ -78,11 +80,20 @@ fn test_function_return_optimization() {
         "function f(){try{a();return}catch{}}",
     ); // function f(){try{a()}catch{}}
 
-    test("function f(){g:return}", "function f(){}");
-    test("function f(){g:{return}}", "function f(){}");
-    test("function f(){g:if(a()){return;}else{return;} return;}", "function f(){g:a()}");
-    test("function f(){g:{if(a()){return;}else{return;} return;}}", "function f(){g:a()}");
-    test("function f(){g:{a();if(b()){return;}else{return;} return;}}", "function f(){g:a(),b()}");
+    test_same("function f(){g:return}"); // function f(){}
+    test("function f(){g:{return}}", "function f(){g:return}"); // function f(){}
+    test(
+        "function f(){g:if(a()){return;}else{return;} return;}",
+        "function f(){g:if(a())return;else return}",
+    ); // function f(){g:a()}
+    test(
+        "function f(){g:{if(a()){return;}else{return;} return;}}",
+        "function f(){g:return a(),void 0}",
+    ); // function f(){g:a()}
+    test(
+        "function f(){g:{a();if(b()){return;}else{return;} return;}}",
+        "function f(){g:return a(),b(),void 0}",
+    ); // function f(){g:a(),b()}
     test(
         "function f(){try{g:if(a()){throw 9;} return;}finally{return}}",
         "function f(){try{g:if(a())throw 9; return}finally{return}}",
@@ -143,12 +154,21 @@ fn test_while_continue_optimization() {
         "for(;;)try{if(a())continue;continue}catch{}",
     ); // for(;;)try{a()}catch{}
 
-    test("while(true){g:continue}", "for(;;);");
-    test("while(true){g:{continue}}", "for(;;);");
+    test("while(true){g:continue}", "for(;;) g:continue;"); // for(;;);
+    test("while(true){g:{continue}}", "for(;;) g:continue;"); // for(;;);
     // This case could be improved.
-    test("while(true){g:if(a()){continue;}else{continue;} continue;}", "for (;;)g:a();");
-    test("while(true){g:{if(a()){continue;}else{continue;} continue;}}", "for(;;)g:a();");
-    test("while(true){g:{a();if(b()){continue;}else{continue;} continue;}}", "for(;;)g:a(),b();");
+    test(
+        "while(true){g:if(a()){continue;}else{continue;} continue;}",
+        "for(;;)g:if(a())continue;else continue;",
+    ); // for (;;)g:a();
+    test(
+        "while(true){g:{if(a()){continue;}else{continue;} continue;}}",
+        "for(;;)g:{if(a())continue;continue}",
+    ); // for(;;)g:a();
+    test(
+        "while(true){g:{a();if(b()){continue;}else{continue;} continue;}}",
+        "for(;;)g:{if(a(),b())continue;continue}",
+    ); // for(;;)g:a(),b();
 }
 
 #[test]
@@ -184,9 +204,12 @@ fn test_do_continue_optimization() {
         "do try{if(a())continue;continue}catch{}while(!0);",
     ); // do try{a()}catch{}while(!0);
 
-    test("do{g:continue}while(true)", "do;while(!0);");
+    test("do{g:continue}while(true)", "do g:continue;while(!0);"); // do;while(!0);
     // This case could be improved.
-    test("do{g:if(a()){continue;}else{continue;} continue;}while(true)", "do g:a();while(!0);");
+    test(
+        "do{g:if(a()){continue;}else{continue;} continue;}while(true)",
+        "do g:if(a())continue;else continue;while(!0);",
+    ); // do g:a();while(!0);
 
     test("do { foo(); continue; } while(false)", "do foo();while(!1)");
     test("do { foo(); break; } while(false)", "do foo();while(!1)");
@@ -267,19 +290,19 @@ fn test_for_continue_optimization() {
         "for(x=0;x<y;x++)try{if(a())continue;continue}catch{}",
     ); // for(x=0;x<y;x++)try{a()}catch{}
 
-    test("for(x=0;x<y;x++){g:continue}", "for(x=0;x<y;x++);");
-    test("for(x=0;x<y;x++){g:{continue}}", "for(x=0;x<y;x++);");
+    test("for(x=0;x<y;x++){g:continue}", "for(x=0;x<y;x++)g:continue;"); // for(x=0;x<y;x++);
+    test("for(x=0;x<y;x++){g:{continue}}", "for(x=0;x<y;x++)g:continue;"); // for(x=0;x<y;x++);
     test(
         "for(x=0;x<y;x++){g:if(a()){continue;}else{continue;} continue;}",
-        "for(x=0;x<y;x++)g:a();",
-    );
+        "for(x=0;x<y;x++)g:if(a())continue;else continue;",
+    ); // for(x=0;x<y;x++)g:a();
     test(
         "for(x=0;x<y;x++){g:{if(a()){continue;}else{continue;} continue;}}",
-        "for(x=0;x<y;x++)g:a();",
-    );
+        "for(x=0;x<y;x++)g:{if(a())continue;continue;}",
+    ); // for(x=0;x<y;x++)g:a();
     test(
         "for(x=0;x<y;x++){g:{a();if(b()){continue;}else{continue;} continue;}}",
-        "for(x=0;x<y;x++)g:a(),b();",
+        "for(x=0;x<y;x++)g:{if(a(),b())continue;continue}",
     );
 }
 

crates/oxc_minifier/tests/peephole/minimize_statements.rs

@@ -205,14 +205,17 @@ fn test_handle_switch_statement() {
     test("switch (a) { case 1: if(a) {b();}c();}", "a === 1 && (a && b(), c());");
     test("switch ('\\v') { case '\\u000B': foo();}", "foo();");
 
-    test("x: switch (a) { case 1: break x;}", "x: if (a === 1) break x;");
+    test("x: switch (a) { case 1: break x;}", "x: switch (a) { case 1: break x; }"); // x: if (a === 1) break x;
     test_same("x: switch (a) { case 2: break x; case 1: break x;}"); // x: { a; break x; }
-    test("x: switch (2) { case 2: f(); break outer; }", "x: { f(); break outer; }");
+    test("x: switch (2) { case 2: f(); break outer; }", "x:switch(2){case 2:f();break outer}"); // x: { f(); break outer; }
     test(
         "x: switch (x) { case 2: f(); for (;;){break outer;}}",
-        "x: if (x === 2) for (f();;) break outer;",
-    );
-    test("x: switch (a) { case 2: if(b) { break outer; } }", "x: if (a === 2 && b) break outer;");
+        "x: switch (x) { case 2: for (f();;)break outer}",
+    ); // x: if (x === 2) for (f();;) break outer;
+    test(
+        "x: switch (a) { case 2: if(b) { break outer; } }",
+        "x: switch (a) { case 2: if(b) break outer; }",
+    ); // x: if (a === 2 && b) break outer;
 
     test(
         "switch ('r') { case 'r': a();break; case 'r': var x=0;break;}",

tasks/track_memory_allocations/allocs_minifier.yaml

@@ -5,7 +5,7 @@ checker.ts:
   sys deallocs: 152
   sys alloc bytes: 14996600 # 15.00 MB
   sys peak growth: 10169560 # 10.17 MB
-  arena allocs: 148493
+  arena allocs: 148428
   arena reallocs: 28468
   arena size: 19205776 # 19.21 MB
 
@@ -71,6 +71,6 @@ kitchen-sink.tsx:
   sys deallocs: 1858
   sys alloc bytes: 5307512 # 5.31 MB
   sys peak growth: 3707425 # 3.71 MB
-  arena allocs: 66806
+  arena allocs: 66771
   arena reallocs: 12252
   arena size: 9424360 # 9.42 MB