For-of loop (#85)

Implements `es2015::for_of`

README.md

@@ -45,7 +45,7 @@ New generation javascript to old-days javascript.
     - [x] computed-properties
     - [x] destructuring
     - [x] duplicate-keys
-    - [ ] for-of
+    - [x] for-of
     - [x] function-name
     - [x] instanceof
     - [x] literals
@@ -77,11 +77,13 @@ New generation javascript to old-days javascript.
 
 The benchmarks were run on Macbook pro, dual core, 2.3GHz Intel Core i5, 16 GB ram
 
-|                       |                performance             |
+|                          |                performance             |
-| --------------------- |:--------------------------------------:|
+| ------------------------ |:--------------------------------------:|
-| swc (ffi)             | 1,086 ops/sec ±0.77% (84 runs sampled) |
+| swc (ffi)                | 1,086 ops/sec ±0.77% (84 runs sampled) |
-| swc-optimize (ffi)    | 1,060 ops/sec ±0.63% (87 runs sampled) |
+| swc-optimize (ffi)       | 1,060 ops/sec ±0.63% (87 runs sampled) |
-| babel                 | 65.72 ops/sec ±6.45% (62 runs sampled) |
+| swc (ffi, simd)          | 1,295 ops/sec ±0.87% (89 runs sampled) |
+| swc-optimize (ffi, simd) | 1,270 ops/sec ±0.24% (89 runs sampled) |
+| babel                    | 65.72 ops/sec ±6.45% (62 runs sampled) |
 
 
 ## Contributing

ecmascript/transforms/src/compat/es2015/for_of/mod.rs

@@ -0,0 +1,432 @@
+use crate::util::{ExprFactory, StmtLike};
+use ast::*;
+use swc_common::{Fold, FoldWith, Mark, Spanned, DUMMY_SP};
+
+#[cfg(test)]
+mod tests;
+
+/// `@babel/plugin-transform-for-of`
+///
+/// ## In
+///
+/// ```js
+/// for (var i of foo) {}
+/// ```
+///
+/// ## Out
+///
+/// ```js
+/// var _iteratorNormalCompletion = true;
+/// var _didIteratorError = false;
+/// var _iteratorError = undefined;
+///
+/// try {
+///   for (var _iterator = foo[Symbol.iterator](), _step; !(_iteratorNormalCompletion = (_step = _iterator.next()).done); _iteratorNormalCompletion = true) {
+///     var i = _step.value;
+///   }
+/// } catch (err) {
+///   _didIteratorError = true;
+///   _iteratorError = err;
+/// } finally {
+///   try {
+///     if (!_iteratorNormalCompletion && _iterator.return != null) {
+///       _iterator.return();
+///     }
+///   } finally {
+///     if (_didIteratorError) {
+///       throw _iteratorError;
+///     }
+///   }
+/// }
+/// ```
+pub fn for_of() -> impl Fold<Module> {
+    ForOf
+}
+
+struct ForOf;
+
+/// Real folder.
+#[derive(Default)]
+struct Actual {
+    ///```js
+    /// var _iteratorNormalCompletion = true;
+    /// var _didIteratorError = false;
+    /// var _iteratorError = undefined;
+    /// ```
+    top_level_vars: Vec<VarDeclarator>,
+}
+
+impl Actual {
+    fn fold_for_stmt(
+        &mut self,
+        label: Option<Ident>,
+        ForOfStmt {
+            span,
+            await_token,
+            left,
+            right,
+            body,
+        }: ForOfStmt,
+    ) -> Stmt {
+        assert!(await_token.is_none());
+        let var_span = left.span().apply_mark(Mark::fresh(Mark::root()));
+        // TODO(kdy): convert to normal for loop if rhs is array
+        // TODO(kdy): Type annotation to determine if rhs is array
+
+        let mut body = match *body {
+            Stmt::Block(block) => block,
+            body => BlockStmt {
+                span: DUMMY_SP,
+                stmts: vec![body],
+            },
+        };
+
+        let step = quote_ident!(var_span, "_step");
+        let step_value = box Expr::Member(MemberExpr {
+            span: DUMMY_SP,
+            obj: ExprOrSuper::Expr(box Expr::Ident(step.clone())),
+            computed: false,
+            prop: box Expr::Ident(quote_ident!("value")),
+        });
+        body.stmts.insert(
+            0,
+            match left {
+                VarDeclOrPat::VarDecl(mut var) => {
+                    assert!(var.decls.len() == 1);
+                    Stmt::Decl(Decl::Var(VarDecl {
+                        span: var.span,
+                        kind: var.kind,
+                        decls: vec![VarDeclarator {
+                            init: Some(step_value),
+                            ..var.decls.pop().unwrap()
+                        }],
+                    }))
+                }
+                VarDeclOrPat::Pat(pat) => Stmt::Expr(box Expr::Assign(AssignExpr {
+                    span: DUMMY_SP,
+                    left: PatOrExpr::Pat(box pat),
+                    op: op!("="),
+                    right: step_value,
+                })),
+            },
+        );
+
+        let iterator = quote_ident!(var_span, "_iterator");
+        // `_iterator.return`
+        let iterator_return = box Expr::Member(MemberExpr {
+            span: DUMMY_SP,
+            obj: ExprOrSuper::Expr(box Expr::Ident(iterator.clone())),
+            computed: false,
+            prop: box Expr::Ident(quote_ident!("return")),
+        });
+
+        let normal_completion_ident = Ident::new("_iteratorNormalCompletion".into(), var_span);
+        self.top_level_vars.push(VarDeclarator {
+            span: DUMMY_SP,
+            name: Pat::Ident(normal_completion_ident.clone()),
+            init: Some(box Expr::Lit(Lit::Bool(Bool {
+                span: DUMMY_SP,
+                value: true,
+            }))),
+        });
+        let error_flag_ident = Ident::new("_didIteratorError".into(), var_span);
+        self.top_level_vars.push(VarDeclarator {
+            span: DUMMY_SP,
+            name: Pat::Ident(error_flag_ident.clone()),
+            init: Some(box Expr::Lit(Lit::Bool(Bool {
+                span: DUMMY_SP,
+                value: false,
+            }))),
+        });
+        let error_ident = Ident::new("_iteratorError".into(), var_span);
+        self.top_level_vars.push(VarDeclarator {
+            span: DUMMY_SP,
+            name: Pat::Ident(error_ident.clone()),
+            init: Some(box Expr::Ident(Ident::new(js_word!("undefined"), DUMMY_SP))),
+        });
+
+        let for_stmt = ForStmt {
+            span,
+            init: Some(VarDeclOrExpr::VarDecl(VarDecl {
+                span: DUMMY_SP,
+                kind: VarDeclKind::Var,
+                decls: vec![
+                    VarDeclarator {
+                        span: DUMMY_SP,
+                        name: Pat::Ident(iterator.clone()),
+                        init: Some(box Expr::Call(CallExpr {
+                            span: DUMMY_SP,
+                            callee: MemberExpr {
+                                span: DUMMY_SP,
+                                obj: ExprOrSuper::Expr(right),
+                                computed: true,
+                                prop: member_expr!(DUMMY_SP, Symbol.iterator),
+                            }
+                            .as_callee(),
+                            args: vec![],
+                        })),
+                    },
+                    VarDeclarator {
+                        span: DUMMY_SP,
+                        name: Pat::Ident(step.clone()),
+                        init: None,
+                    },
+                ],
+            })),
+            // !(_iteratorNormalCompletion = (_step = _iterator.next()).done)
+            test: Some(box Expr::Unary(UnaryExpr {
+                span: DUMMY_SP,
+                op: op!("!"),
+                arg: box Expr::Paren(ParenExpr {
+                    span: DUMMY_SP,
+                    expr: box Expr::Member(MemberExpr {
+                        span: DUMMY_SP,
+                        obj: ExprOrSuper::Expr(box Expr::Assign(AssignExpr {
+                            span: DUMMY_SP,
+                            left: PatOrExpr::Pat(box Pat::Ident(normal_completion_ident.clone())),
+                            op: op!("="),
+                            right: box Expr::Paren(ParenExpr {
+                                span: DUMMY_SP,
+                                expr: box Expr::Assign(AssignExpr {
+                                    span: DUMMY_SP,
+                                    left: PatOrExpr::Pat(box Pat::Ident(step.clone())),
+                                    op: op!("="),
+                                    // `_iterator.next()`
+                                    right: box Expr::Call(CallExpr {
+                                        span: DUMMY_SP,
+                                        // `_iterator.next`
+                                        callee: MemberExpr {
+                                            span: DUMMY_SP,
+                                            computed: false,
+                                            obj: ExprOrSuper::Expr(box Expr::Ident(
+                                                iterator.clone(),
+                                            )),
+                                            prop: member_expr!(DUMMY_SP, next),
+                                        }
+                                        .as_callee(),
+                                        args: vec![],
+                                    }),
+                                }),
+                            }),
+                        })),
+                        computed: false,
+                        prop: box Expr::Ident(quote_ident!("done")),
+                    }),
+                }),
+            })),
+
+            // `_iteratorNormalCompletion = true`
+            update: Some(box Expr::Assign(AssignExpr {
+                span: DUMMY_SP,
+                left: PatOrExpr::Pat(box Pat::Ident(normal_completion_ident.clone())),
+                op: op!("="),
+                right: box Expr::Lit(Lit::Bool(Bool {
+                    span: DUMMY_SP,
+                    value: true,
+                })),
+            })),
+            body: box Stmt::Block(body),
+        }
+        .into();
+
+        let for_stmt = match label {
+            Some(label) => Stmt::Labeled(LabeledStmt {
+                span,
+                label,
+                body: box for_stmt,
+            }),
+            None => for_stmt,
+        };
+
+        Stmt::Try(TryStmt {
+            span: DUMMY_SP,
+            block: BlockStmt {
+                span: DUMMY_SP,
+                stmts: vec![for_stmt],
+            },
+            handler: Some(CatchClause {
+                span: DUMMY_SP,
+                param: Some(Pat::Ident(quote_ident!("err"))),
+                // _didIteratorError = true;
+                // _iteratorError = err;
+                body: BlockStmt {
+                    span: DUMMY_SP,
+                    stmts: vec![
+                        // _didIteratorError = true;
+                        Stmt::Expr(box Expr::Assign(AssignExpr {
+                            span: DUMMY_SP,
+                            left: PatOrExpr::Pat(box Pat::Ident(error_flag_ident.clone())),
+                            op: op!("="),
+                            right: box Expr::Lit(Lit::Bool(Bool {
+                                span: DUMMY_SP,
+                                value: true,
+                            })),
+                        })),
+                        // _iteratorError = err;
+                        Stmt::Expr(box Expr::Assign(AssignExpr {
+                            span: DUMMY_SP,
+                            left: PatOrExpr::Pat(box Pat::Ident(error_ident.clone())),
+                            op: op!("="),
+                            right: box Expr::Ident(quote_ident!("err")),
+                        })),
+                    ],
+                },
+            }),
+            finalizer: Some(BlockStmt {
+                span: DUMMY_SP,
+                stmts: vec![make_finally_block(
+                    iterator_return,
+                    &normal_completion_ident,
+                    error_flag_ident,
+                    error_ident,
+                )],
+            }),
+        })
+    }
+}
+
+impl Fold<Stmt> for Actual {
+    fn fold(&mut self, stmt: Stmt) -> Stmt {
+        match stmt {
+            Stmt::Labeled(LabeledStmt { span, label, body }) => {
+                // Handle label
+                match *body {
+                    Stmt::ForOf(
+                        stmt @ ForOfStmt {
+                            await_token: None, ..
+                        },
+                    ) => self.fold_for_stmt(Some(label), stmt),
+                    _ => {
+                        return Stmt::Labeled(LabeledStmt {
+                            span,
+                            label,
+                            body: body.fold_children(self),
+                        });
+                    }
+                }
+            }
+            Stmt::ForOf(
+                stmt @ ForOfStmt {
+                    await_token: None, ..
+                },
+            ) => self.fold_for_stmt(None, stmt),
+            _ => stmt.fold_children(self),
+        }
+    }
+}
+
+/// ```js
+/// 
+///   try {
+///     if (!_iteratorNormalCompletion && _iterator.return != null) {
+///       _iterator.return();
+///     }
+///   } finally {
+///     if (_didIteratorError) {
+///       throw _iteratorError;
+///     }
+///   }
+/// ```
+fn make_finally_block(
+    iterator_return: Box<Expr>,
+    normal_completion_ident: &Ident,
+    error_flag_ident: Ident,
+    error_ident: Ident,
+) -> Stmt {
+    Stmt::Try(TryStmt {
+        span: DUMMY_SP,
+        block: BlockStmt {
+            span: DUMMY_SP,
+            stmts: vec![
+                // if (!_iteratorNormalCompletion && _iterator.return !=
+                // null) {
+                //   _iterator.return();
+                // }
+                Stmt::If(IfStmt {
+                    span: DUMMY_SP,
+                    test: box Expr::Bin(BinExpr {
+                        span: DUMMY_SP,
+                        left: box Expr::Unary(UnaryExpr {
+                            span: DUMMY_SP,
+                            op: op!("!"),
+                            arg: box Expr::Ident(normal_completion_ident.clone()),
+                        }),
+                        op: op!("&&"),
+                        right: box Expr::Bin(BinExpr {
+                            span: DUMMY_SP,
+                            left: iterator_return.clone(),
+                            op: op!("!="),
+                            right: box Expr::Lit(Lit::Null(Null { span: DUMMY_SP })),
+                        }),
+                    }),
+                    cons: box Stmt::Block(BlockStmt {
+                        span: DUMMY_SP,
+                        stmts: vec![Stmt::Expr(box Expr::Call(CallExpr {
+                            span: DUMMY_SP,
+                            callee: iterator_return.as_callee(),
+                            args: vec![],
+                        }))],
+                    }),
+                    alt: None,
+                }),
+            ],
+        },
+        handler: None,
+        finalizer: Some(BlockStmt {
+            span: DUMMY_SP,
+
+            stmts: vec![
+                // if (_didIteratorError) {
+                //   throw _iteratorError;
+                // }
+                Stmt::If(IfStmt {
+                    span: DUMMY_SP,
+                    test: box Expr::Ident(error_flag_ident),
+                    cons: box Stmt::Block(BlockStmt {
+                        span: DUMMY_SP,
+                        stmts: vec![Stmt::Throw(ThrowStmt {
+                            span: DUMMY_SP,
+                            arg: box Expr::Ident(error_ident),
+                        })],
+                    }),
+                    alt: None,
+                }),
+            ],
+        }),
+    })
+}
+
+impl<T: StmtLike> Fold<Vec<T>> for ForOf
+where
+    Vec<T>: FoldWith<Self>,
+{
+    fn fold(&mut self, stmts: Vec<T>) -> Vec<T> {
+        let stmts = stmts.fold_children(self);
+
+        let mut buf = Vec::with_capacity(stmts.len());
+
+        for stmt in stmts {
+            match stmt.try_into_stmt() {
+                Err(module_item) => buf.push(module_item),
+                Ok(stmt) => {
+                    let mut folder = Actual::default();
+                    let stmt = stmt.fold_with(&mut folder);
+
+                    // Add variable declaration
+                    // e.g. var ref
+                    if !folder.top_level_vars.is_empty() {
+                        buf.push(T::from_stmt(Stmt::Decl(Decl::Var(VarDecl {
+                            span: DUMMY_SP,
+                            kind: VarDeclKind::Var,
+                            decls: folder.top_level_vars,
+                        }))));
+                    }
+
+                    buf.push(T::from_stmt(stmt));
+                }
+            }
+        }
+
+        buf
+    }
+}

ecmascript/transforms/src/compat/es2015/for_of/tests.rs

@@ -0,0 +1,226 @@
+use super::*;
+
+test!(
+    ForOf,
+    spec_identifier,
+    r#"for (i of arr) {
+}"#,
+    r#"var _iteratorNormalCompletion = true, _didIteratorError = false, _iteratorError = undefined;
+
+try {
+  for (var _iterator = arr[Symbol.iterator](), _step; !(_iteratorNormalCompletion = (_step = _iterator.next()).done); _iteratorNormalCompletion = true) {
+    i = _step.value;
+  }
+} catch (err) {
+  _didIteratorError = true;
+  _iteratorError = err;
+} finally {
+  try {
+    if (!_iteratorNormalCompletion && _iterator.return != null) {
+      _iterator.return();
+    }
+  } finally {
+    if (_didIteratorError) {
+      throw _iteratorError;
+    }
+  }
+}"#,ok_if_code_eq
+);
+
+test!(ForOf, spec_ignore_cases, r#"for (var i of foo) {
+  switch (i) {
+    case 1:
+      break;
+  }
+}"#, r#"var _iteratorNormalCompletion = true, _didIteratorError = false, _iteratorError = undefined;
+
+try {
+  for (var _iterator = foo[Symbol.iterator](), _step; !(_iteratorNormalCompletion = (_step = _iterator.next()).done); _iteratorNormalCompletion = true) {
+    var i = _step.value;
+
+    switch (i) {
+      case 1:
+        break;
+    }
+  }
+} catch (err) {
+  _didIteratorError = true;
+  _iteratorError = err;
+} finally {
+  try {
+    if (!_iteratorNormalCompletion && _iterator.return != null) {
+      _iterator.return();
+    }
+  } finally {
+    if (_didIteratorError) {
+      throw _iteratorError;
+    }
+  }
+}"#, ok_if_code_eq);
+
+test!(ForOf, spec_let, r#"for (let i of arr) {
+
+}"#, r#"
+var _iteratorNormalCompletion = true, _didIteratorError = false, _iteratorError = undefined;
+
+try {
+  for (var _iterator = arr[Symbol.iterator](), _step; !(_iteratorNormalCompletion = (_step = _iterator.next()).done); _iteratorNormalCompletion = true) {
+    let i = _step.value;
+  }
+} catch (err) {
+  _didIteratorError = true;
+  _iteratorError = err;
+} finally {
+  try {
+    if (!_iteratorNormalCompletion && _iterator.return != null) {
+      _iterator.return();
+    }
+  } finally {
+    if (_didIteratorError) {
+      throw _iteratorError;
+    }
+  }
+}"#,
+ok_if_code_eq);
+
+test!(ForOf, spec_member_expr, r#"for (obj.prop of arr) {
+
+}"#, r#"var _iteratorNormalCompletion = true, _didIteratorError = false, _iteratorError = undefined;
+
+try {
+  for (var _iterator = arr[Symbol.iterator](), _step; !(_iteratorNormalCompletion = (_step = _iterator.next()).done); _iteratorNormalCompletion = true) {
+    obj.prop = _step.value;
+  }
+} catch (err) {
+  _didIteratorError = true;
+  _iteratorError = err;
+} finally {
+  try {
+    if (!_iteratorNormalCompletion && _iterator.return != null) {
+      _iterator.return();
+    }
+  } finally {
+    if (_didIteratorError) {
+      throw _iteratorError;
+    }
+  }
+}"#,
+ok_if_code_eq);
+
+test!(ForOf, spec_multiple, r#"for (var i of arr) {
+
+}
+
+for (var i of numbers) {
+
+}
+"#, r#"var _iteratorNormalCompletion = true, _didIteratorError = false, _iteratorError = undefined;
+
+try {
+  for (var _iterator = arr[Symbol.iterator](), _step; !(_iteratorNormalCompletion = (_step = _iterator.next()).done); _iteratorNormalCompletion = true) {
+    var i = _step.value;
+  }
+} catch (err) {
+  _didIteratorError = true;
+  _iteratorError = err;
+} finally {
+  try {
+    if (!_iteratorNormalCompletion && _iterator.return != null) {
+      _iterator.return();
+    }
+  } finally {
+    if (_didIteratorError) {
+      throw _iteratorError;
+    }
+  }
+}
+
+var _iteratorNormalCompletion1 = true, _didIteratorError1 = false, _iteratorError1 = undefined;
+
+try {
+  for (var _iterator1 = numbers[Symbol.iterator](), _step1; !(_iteratorNormalCompletion1 = (_step1 = _iterator1.next()).done); _iteratorNormalCompletion1 = true) {
+    var i = _step1.value;
+  }
+} catch (err) {
+  _didIteratorError1 = true;
+  _iteratorError1 = err;
+} finally {
+  try {
+    if (!_iteratorNormalCompletion1 && _iterator1.return != null) {
+      _iterator1.return();
+    }
+  } finally {
+    if (_didIteratorError1) {
+      throw _iteratorError1;
+    }
+  }
+}"#, ok_if_code_eq);
+
+test!(ForOf, spec_nested_label_for_of, r#"b: for (let c of d()) {
+  for (let e of f()) {
+    continue b;
+  }
+}"#, r#"var _iteratorNormalCompletion = true, _didIteratorError = false, _iteratorError = undefined;
+
+try {
+  b: for (var _iterator = d()[Symbol.iterator](), _step; !(_iteratorNormalCompletion = (_step = _iterator.next()).done); _iteratorNormalCompletion = true) {
+    let c = _step.value;
+    var _iteratorNormalCompletion1 = true, _didIteratorError1 = false, _iteratorError1 = undefined;
+
+    try {
+      for (var _iterator1 = f()[Symbol.iterator](), _step1; !(_iteratorNormalCompletion1 = (_step1 = _iterator1.next()).done); _iteratorNormalCompletion1 = true) {
+        let e = _step1.value;
+        continue b;
+      }
+    } catch (err) {
+      _didIteratorError1 = true;
+      _iteratorError1 = err;
+    } finally {
+      try {
+        if (!_iteratorNormalCompletion1 && _iterator1.return != null) {
+          _iterator1.return();
+        }
+      } finally {
+        if (_didIteratorError1) {
+          throw _iteratorError1;
+        }
+      }
+    }
+  }
+} catch (err) {
+  _didIteratorError = true;
+  _iteratorError = err;
+} finally {
+  try {
+    if (!_iteratorNormalCompletion && _iterator.return != null) {
+      _iterator.return();
+    }
+  } finally {
+    if (_didIteratorError) {
+      throw _iteratorError;
+    }
+  }
+}"#, ok_if_code_eq);
+
+test!(ForOf, spec_var, r#"for (var i of arr) {
+
+}"#, r#"var _iteratorNormalCompletion = true, _didIteratorError = false, _iteratorError = undefined;
+
+try {
+  for (var _iterator = arr[Symbol.iterator](), _step; !(_iteratorNormalCompletion = (_step = _iterator.next()).done); _iteratorNormalCompletion = true) {
+    var i = _step.value;
+  }
+} catch (err) {
+  _didIteratorError = true;
+  _iteratorError = err;
+} finally {
+  try {
+    if (!_iteratorNormalCompletion && _iterator.return != null) {
+      _iterator.return();
+    }
+  } finally {
+    if (_didIteratorError) {
+      throw _iteratorError;
+    }
+  }
+}"#, ok_if_code_eq);

ecmascript/transforms/src/compat/es2015/mod.rs

@@ -1,8 +1,8 @@
 pub use self::{
     arrow::arrow, block_scoped_fn::BlockScopedFns, block_scoping::block_scoping, classes::Classes,
     computed_props::computed_properties, destructuring::destructuring,
-    duplicate_keys::duplicate_keys, function_name::function_name, instanceof::InstanceOf,
+    duplicate_keys::duplicate_keys, for_of::for_of, function_name::function_name,
-    parameters::parameters, shorthand_property::Shorthand, spread::Spread,
+    instanceof::InstanceOf, parameters::parameters, shorthand_property::Shorthand, spread::Spread,
     sticky_regex::StickyRegex, template_literal::TemplateLiteral, typeof_symbol::TypeOfSymbol,
 };
 use super::helpers::Helpers;
@@ -17,6 +17,7 @@ mod classes;
 mod computed_props;
 mod destructuring;
 mod duplicate_keys;
+mod for_of;
 mod function_name;
 mod instanceof;
 mod parameters;
@@ -66,6 +67,7 @@ pub fn es2015(helpers: &Arc<Helpers>) -> impl Fold<Module> {
     chain_at!(
         Module,
         stmts(helpers),
+        for_of(),
         computed_properties(helpers.clone()),
         destructuring(helpers.clone()),
         block_scoping(),

ecmascript/transforms/src/hygiene.rs

@@ -283,4 +283,62 @@ mod tests {
         );
     }
 
+    #[test]
+    fn for_loop() {
+        test(
+            |tester| {
+                let mark1 = Mark::fresh(Mark::root());
+                let mark2 = Mark::fresh(mark1);
+                let mark3 = Mark::fresh(mark1);
+
+                Ok(vec![
+                    tester
+                        .parse_stmt("actual1.js", "for(var a=1;;) {}")?
+                        .fold_with(&mut marker(&[("a", mark1)])),
+                    tester
+                        .parse_stmt("actual2.js", "for(var a of foo) {}")?
+                        .fold_with(&mut marker(&[("a", mark2)])),
+                    tester
+                        .parse_stmt("actual3.js", "for(var a=3;;) {}")?
+                        .fold_with(&mut marker(&[("a", mark3)])),
+                ])
+            },
+            "
+            for(var a=1;;) {}
+            for(var a1 of foo) {}
+            for(var a2 = 3;;) {}
+            ",
+        );
+    }
+
+    #[test]
+    fn try_for_loop() {
+        test(
+            |tester| {
+                let mark1 = Mark::fresh(Mark::root());
+                let mark2 = Mark::fresh(mark1);
+                let mark3 = Mark::fresh(mark1);
+
+                Ok(vec![
+                    tester
+                        .parse_stmt("actual1.js", "try { for(var a=1;;) {} } finally {}")?
+                        .fold_with(&mut marker(&[("a", mark1)])),
+                    tester
+                        .parse_stmt("actual2.js", "for(var a of foo) {}")?
+                        .fold_with(&mut marker(&[("a", mark2)])),
+                    tester
+                        .parse_stmt("actual3.js", "for(var a=3;;) {}")?
+                        .fold_with(&mut marker(&[("a", mark3)])),
+                ])
+            },
+            "
+            try {
+                for(var a=1;;) {}
+            } finally {
+            }
+            for(var a1 of foo) {}
+            for(var a2 = 3;;) {}
+            ",
+        );
+    }
 }

ecmascript/transforms/src/scope.rs

@@ -148,6 +148,17 @@ impl<'a, 'b, T: Traverse> Fold<Module> for ScopeAnalyzer<'a, 'b, T> {
     }
 }
 
+impl<'a, 'b, T: Traverse> Fold<TryStmt> for ScopeAnalyzer<'a, 'b, T> {
+    fn fold(&mut self, node: TryStmt) -> TryStmt {
+        TryStmt {
+            span: node.span,
+            block: node.block.fold_children(self),
+            handler: node.handler.fold_with(self),
+            finalizer: node.finalizer.fold_children(self),
+        }
+    }
+}
+
 impl<'a, 'b, T: Traverse> Fold<BlockStmt> for ScopeAnalyzer<'a, 'b, T> {
     fn fold(&mut self, node: BlockStmt) -> BlockStmt {
         let node = {