decaffeinate crashes with a thin arrow function in an object

decaffeinate is crashing on my CoffeeScript input:

# Bad
prop: (x) -> x

# OK
#prop: (x) => x

# Also OK
#func((x) -> x)

if Babel is configured to target fairly old browsers as follows:

// babel.config.js

module.exports = {
  presets: [
    // Bad
    ["@babel/preset-env", { targets: ["IE 11"] }],
    // OK
    //["@babel/preset-env", { targets: ["last 1 Chrome version"] }],
  ],
};

Minimal reproducible setup is here https://gitlab.com/uasi/20191112-decaffeinate-crash

I get this error:

/Users/uasi/tmp/decaf/node_modules/decaffeinate/dist/cli.js:304
        throw err;
        ^

RangeError: unknown: Maximum call stack size exceeded
    at Object.get [as isBlockScoped] (/Users/uasi/tmp/decaf/node_modules/@babel/types/lib/index.js:286:17)
    at Object.checkPath (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/path/lib/virtual-types.js:118:14)
    at Object.newFn (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/visitors.js:215:17)
    at NodePath._call (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/path/context.js:55:20)
    at NodePath.call (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/path/context.js:38:14)
    at NodePath.visit (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/path/context.js:90:31)
    at TraversalContext.visitQueue (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/context.js:112:16)
    at TraversalContext.visitSingle (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/context.js:84:19)
    at TraversalContext.visit (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/context.js:140:19)
    at Function.traverse.node (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/index.js:84:17)
    at NodePath.visit (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/path/context.js:97:18)
    at TraversalContext.visitQueue (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/context.js:112:16)
    at TraversalContext.visitMultiple (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/context.js:79:17)
    at TraversalContext.visit (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/context.js:138:19)
    at Function.traverse.node (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/index.js:84:17)
    at NodePath.visit (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/path/context.js:97:18)
    at TraversalContext.visitQueue (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/context.js:112:16)
    at TraversalContext.visitSingle (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/context.js:84:19)
    at TraversalContext.visit (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/context.js:140:19)
    at Function.traverse.node (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/index.js:84:17)
    at traverse (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/index.js:66:12)
    at NodePath.traverse (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/path/index.js:148:24)
    at Scope.crawl (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/scope/index.js:639:10)
    at Scope.init (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/scope/index.js:589:32)
    at NodePath.setScope (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/path/context.js:131:30)
    at NodePath.replaceWith (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/path/replacement.js:159:8)
    at PluginPass.ObjectProperty (/Users/uasi/tmp/decaf/node_modules/@resugar/codemod-objects-concise/src/index.js:20:22)
    at newFn (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/visitors.js:179:21)
    at NodePath._call (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/path/context.js:55:20)
    at NodePath.call (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/path/context.js:42:17)
    at NodePath.visit (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/path/context.js:90:31)
    at TraversalContext.visitQueue (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/context.js:112:16)
    at TraversalContext.visitQueue (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/context.js:118:21)
    at TraversalContext.visitQueue (/Users/uasi/tmp/decaf/node_modules/@babel/traverse/lib/context.js:118:21)


...

[eventualbuddha]

🎉 This issue has been resolved in version 6.1.9 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀

[uasi]

I think I found the root cause.

We can reproduce this bug only using the @babel/plugin-transform-shorthand-properties plugin, which is a part of @babel/preset-env.

// input.coffee

prop: (x) -> x

// babel.config.js

module.exports = {
  plugins: [
    ["@babel/plugin-transform-shorthand-properties"],
  ],
}

It transforms concise methods to longer form ({ func() {...} } -> { func: function() {...} }), while the @resugar/codemod-objects-concise plugin used by decaffeinate does the opposite.

• https://github.com/babel/babel/blob/v7.8.3/packages/babel-plugin-transform-shorthand-properties/src/index.js#L11-L25
• https://github.com/resugar/resugar/blob/83f1ead58ee01992b8bc571f7e510512bf24a164/packages/resugar-codemod-objects-concise/src/index.ts#L9-L24

Maybe these plugins rewrite each other’s output endlessly.