feat(es/minifier): Drop cycles in nested functions (#5933)

crates/swc_ecma_minifier/tests/TODO.txt

@@ -162,7 +162,6 @@ drop_unused/issue_t161_top_retain_9/input.js
 drop_unused/issue_t183/input.js
 drop_unused/keep_assign/input.js
 drop_unused/reassign_const/input.js
-drop_unused/unused_circular_references_1/input.js
 drop_unused/unused_circular_references_2/input.js
 drop_unused/unused_circular_references_3/input.js
 drop_unused/var_catch_toplevel/input.js

crates/swc_ecma_minifier/tests/passing.txt

@@ -438,6 +438,7 @@ drop_unused/issue_t161_top_retain_7/input.js
 drop_unused/keep_fnames/input.js
 drop_unused/unused_block_decls/input.js
 drop_unused/unused_block_decls_in_catch/input.js
+drop_unused/unused_circular_references_1/input.js
 drop_unused/unused_class_which_extends_might_throw/input.js
 drop_unused/unused_class_which_might_throw/input.js
 drop_unused/unused_class_which_might_throw_2/input.js

crates/swc_ecma_transforms_optimization/src/simplify/dce/mod.rs

@@ -216,6 +216,7 @@ struct Analyzer<'a> {
 #[derive(Debug, Default)]
 struct Scope<'a> {
     parent: Option<&'a Scope<'a>>,
+    kind: ScopeKind,
 
     bindings_affected_by_eval: AHashSet<Id>,
     found_direct_eval: bool,
@@ -235,6 +236,12 @@ enum ScopeKind {
     ArrowFn,
 }
 
+impl Default for ScopeKind {
+    fn default() -> Self {
+        Self::Fn
+    }
+}
+
 impl Analyzer<'_> {
     fn with_ast_path<F>(&mut self, ids: Vec<Id>, op: F)
     where
@@ -327,6 +334,10 @@ impl Analyzer<'_> {
                         .add_dep_edge(component.clone(), id.clone(), assign)
                 }
 
+                if s.kind == ScopeKind::Fn && !s.ast_path.is_empty() {
+                    break;
+                }
+
                 scope = s.parent;
             }
         }

crates/swc_ecma_transforms_optimization/tests/dce/cycle-5/input.js

@@ -0,0 +1,10 @@
+export function f(x, y) {
+    function g() {
+        return h();
+    }
+    function h() {
+        return g();
+    }
+    return x + y;
+}
+

crates/swc_ecma_transforms_optimization/tests/dce/cycle-5/output.full.js

@@ -0,0 +1,3 @@
+export function f(x, y) {
+    return x + y;
+}

crates/swc_ecma_transforms_optimization/tests/dce/cycle-5/output.js

@@ -0,0 +1,3 @@
+export function f(x, y) {
+    return x + y;
+}