feat(minifier): remove unreachable statements after break and continue (#8743)

Author: Boshen

crates/oxc_minifier/src/peephole/remove_dead_code.rs

@@ -23,10 +23,10 @@ impl<'a, 'b> PeepholeOptimizations {
         stmts: &mut Vec<'a, Statement<'a>>,
         ctx: Ctx<'a, '_>,
     ) {
+        self.dead_code_elimination(stmts, ctx);
         if stmts.iter().any(|stmt| matches!(stmt, Statement::EmptyStatement(_))) {
             stmts.retain(|stmt| !matches!(stmt, Statement::EmptyStatement(_)));
         }
-        self.dead_code_elimination(stmts, ctx);
     }
 
     pub fn remove_dead_code_exit_statement(&mut self, stmt: &mut Statement<'a>, ctx: Ctx<'a, '_>) {
@@ -68,20 +68,19 @@ impl<'a, 'b> PeepholeOptimizations {
         }
     }
 
-    /// Removes dead code thats comes after `return` statements after inlining `if` statements
+    /// Removes dead code thats comes after `return`, `throw`, `continue` and `break` statements.
     fn dead_code_elimination(&mut self, stmts: &mut Vec<'a, Statement<'a>>, ctx: Ctx<'a, 'b>) {
         // Remove code after `return` and `throw` statements
         let mut index = None;
         'outer: for (i, stmt) in stmts.iter().enumerate() {
-            if matches!(stmt, Statement::ReturnStatement(_) | Statement::ThrowStatement(_)) {
+            if Self::is_unreachable_statement(stmt) {
                 index.replace(i);
                 break;
             }
             // Double check block statements folded by if statements above
             if let Statement::BlockStatement(block_stmt) = stmt {
                 for stmt in &block_stmt.body {
-                    if matches!(stmt, Statement::ReturnStatement(_) | Statement::ThrowStatement(_))
-                    {
+                    if Self::is_unreachable_statement(stmt) {
                         index.replace(i);
                         break 'outer;
                     }
@@ -129,6 +128,16 @@ impl<'a, 'b> PeepholeOptimizations {
         }
     }
 
+    fn is_unreachable_statement(stmt: &Statement<'a>) -> bool {
+        matches!(
+            stmt,
+            Statement::ReturnStatement(_)
+                | Statement::ThrowStatement(_)
+                | Statement::BreakStatement(_)
+                | Statement::ContinueStatement(_)
+        )
+    }
+
     /// Remove block from single line blocks
     /// `{ block } -> block`
     fn try_optimize_block(
@@ -915,4 +924,12 @@ mod test {
         test("foo(...[])", "foo()");
         test("new Foo(...[])", "new Foo()");
     }
+
+    #[test]
+    fn remove_unreachable() {
+        test("while(true) { break a; unreachable;}", "for(;;) break a");
+        test("while(true) { continue a; unreachable;}", "for(;;) continue a");
+        test("while(true) { throw a; unreachable;}", "for(;;) throw a");
+        test("while(true) { return a; unreachable;}", "for(;;) return a");
+    }
 }