Mangle function name duplicate with the parameter name

[noyobo]

Describe the bug

output code:

export function __CREATE_EXP__() {
    return function n(...n) { // n is duplicate
        return value;
    };
}

run in Safari throw error:

SyntaxError: Duplicate parameter 'e2' not allowed in function with a rest parameter.

But it works in chrome...

Input code

export function __CREATE_EXP__() {
  return function EXP(...args) {
      return value;
  };
}

Config

{
  "jsc": {
    "parser": {
      "syntax": "typescript",
      "tsx": false
    },
    "externalHelpers": true,
    "target": "es2015",
    "loose": false,
    "minify": {
      "compress": false,
      "mangle": {
        "toplevel": false,
        "keep_classnames": false,
        "keep_fnames": false,
        "keep_private_props": false,
        "ie8": false,
        "safari10": false
      }
    }
  },
  "module": {
    "type": "es6"
  },
  "minify": false,
  "isModule": true
}

Playground link

https://play.swc.rs/?version=1.3.26&code=H4sIAAAAAAAAA0utKMgvKlFIK81LLsnMz1OIj3cOcnUMcY13jQiIj9fQVKjmUlAoSi0pLcpDKALKaejp6SUWpRdDFIAAVFFZYk5pqjVQrNaaq5YLAMflGI9fAAAA&config=H4sIAAAAAAAAA22PQQrCQAxF75J1Fyoo0hO48QwS6q%2BMTmdCEqVFenenUi2Cq4T%2F85O8J12tofpJwmrQqbMhOfdUkw8CazSIU0VuRWo5GsaK0Ds0cTwgCtSodr2jzLBe4CUJ26zW25KKORvmXEVdSKEdphtN7kRhtlicLhGT5VkiHohf6wbIqYlslriD%2FertH000PNhRapbFCth%2Fe%2BOWNaxXH6KxMHX5fJ8%2FKNxviB2Ny9OfNXacByfm8QVyauLJQAEAAA%3D%3D

Expected behavior

export function __CREATE_EXP__() {
    return function EXP(...n) { //  EXP name ? 
        return value;
    };
}

Actual behavior

No response

Version

1.3.26

Additional context

No response

[noyobo]

Related issue？#6730

[kdy1]

I didn't know that a rest parameter behaves differently than a normal parameter...

[noyobo]

In this file and the closure scope, EXP is just a function display name, which is convenient for me to debug in devtools, and there is no reference.

[kdy1]

@iheyunfei Do you have any idea to fix this?
I'm now thinking about the way, but my solution requires a strange scoping trick.

[hyf0]

---

edited:

I just check it, it's not right. Let me do some digging.

---

Yeah. A simple way is adding a line like

fn visit_fn_decl(&mut self, f: &FnDecl) {
        self.add_decl(f.ident.to_id(), true);

        self.with_fn_scope(|v| {
+            v.add_usage(f.ident.to_id());
            f.function.decorators.visit_with(v);
            f.function.params.visit_with(v);
            // WARN: Option<BlockStmt>::visit_mut_children_wth
            // is not same with BlockStmt::visit_mut_children_wth
            v.visit_fn_body_within_same_scope(&f.function.body);
        })
    }

in

swc/crates/swc_ecma_transforms_base/src/rename/analyzer/mod.rs

Lines 270 to 280 in 179a5f8

	fn visit_fn_decl(&mut self, f: &FnDecl) {
	self.add_decl(f.ident.to_id(), true);
	self.with_fn_scope(|v| {
	f.function.decorators.visit_with(v);
	f.function.params.visit_with(v);
	// WARN: Option<BlockStmt>::visit_mut_children_wth
	// is not same with BlockStmt::visit_mut_children_wth
	v.visit_fn_body_within_same_scope(&f.function.body);
	})
	}

FnExpr should also have this issue.

[kdy1]

Thank you! I'll try

[kdy1]

Oh, I think it will regress all cases.

[kdy1]

I'll check for rest and apply your patch 😄

[hyf0]

The idea is correct in general. But the code I provided seems wrong. We need to create fake usages for names that could be conflicting with others.

I also look out Terser, the outputs are

edited:

I just check it, it's not right. Let me do some digging.

Yeah. A simple way is adding a line like

fn visit_fn_decl(&mut self, f: &FnDecl) {
        self.add_decl(f.ident.to_id(), true);

        self.with_fn_scope(|v| {
+            v.add_usage(f.ident.to_id());
            f.function.decorators.visit_with(v);
            f.function.params.visit_with(v);
            // WARN: Option<BlockStmt>::visit_mut_children_wth
            // is not same with BlockStmt::visit_mut_children_wth
            v.visit_fn_body_within_same_scope(&f.function.body);
        })
    }

in

swc/crates/swc_ecma_transforms_base/src/rename/analyzer/mod.rs

Lines 270 to 280 in 179a5f8

	fn visit_fn_decl(&mut self, f: &FnDecl) {
	self.add_decl(f.ident.to_id(), true);
	self.with_fn_scope(|v| {
	f.function.decorators.visit_with(v);
	f.function.params.visit_with(v);
	// WARN: Option<BlockStmt>::visit_mut_children_wth
	// is not same with BlockStmt::visit_mut_children_wth
	v.visit_fn_body_within_same_scope(&f.function.body);
	})
	}

FnExpr should also have this issue.

[kdy1]

It was correct for FnExpr. See: #6821

[kdy1]

Thank you! I fixed it by creating a fake usage

[swc-bot]

This closed issue has been automatically locked because it had no new activity for a month. If you are running into a similar issue, please create a new issue with the steps to reproduce. Thank you.