Exception thrown when imported type has same name as local value

[OliverJAsh]

Your Environment

• Prettier version: 2.8.4
• node version 16.3.0:
• package manager: yarn@2
• IDE: VS Code

Describe the bug

The following code sample produces 0 type errors but causes Prettier to throw:

types.ts:

export type Demo = () => null;

main.ts:

import { Demo } from './types';

const Demo: Demo = () => null

export {}

To Reproduce

See above.

Expected behavior

No error, seeing as this works fine when disabling the Prettier plugin.

Screenshots, code sample, etc

Configuration File (cat .prettierrc, prettier.config.js, .prettier.js)

None.

Error log

["ERROR" - 12:14:21] Identifier 'Demo' has already been declared. (3:6)
  1 | import { Demo } from './types';
  2 |
  3 | const Demo: Demo = () => null;
  4 |
  5 | export {}
SyntaxError: Identifier 'Demo' has already been declared. (3:6)
  1 | import { Demo } from './types';
  2 |
  3 | const Demo: Demo = () => null;
  4 |
  5 | export {}
    at instantiate (/Users/oliverash/Development/temp/prettier-sort-imports-plugin-bug/node_modules/@trivago/prettier-plugin-sort-imports/node_modules/@babel/parser/src/parse-error/credentials.js:61:22)
    at toParseError (/Users/oliverash/Development/temp/prettier-sort-imports-plugin-bug/node_modules/@trivago/prettier-plugin-sort-imports/node_modules/@babel/parser/src/parse-error.js:58:12)
    at Parser.raise (/Users/oliverash/Development/temp/prettier-sort-imports-plugin-bug/node_modules/@trivago/prettier-plugin-sort-imports/node_modules/@babel/parser/src/tokenizer/index.js:1736:19)
    at TypeScriptScopeHandler.checkRedeclarationInScope (/Users/oliverash/Development/temp/prettier-sort-imports-plugin-bug/node_modules/@trivago/prettier-plugin-sort-imports/node_modules/@babel/parser/src/util/scope.js:153:19)

Contribute to @trivago/prettier-plugin-sort-imports

• I'm willing to fix this bug 🥇

---

This issue only happens when @trivago/prettier-plugin-sort-imports is enabled.

[ayusharma]

You are defining Demo as a type and after that re-defining as const.

Can you try this :

types.ts:

export type Demo = () => null;

main.ts:

import { Demo as DemoType } from './types';

const Demo: DemoType = () => null

export {}

Feel free to re-open if the issue exists.

[OliverJAsh]

You are defining Demo as a type and after that re-defining as const.

I understand that, but this is in fact valid TypeScript. If we use tsc or prettier without this plugin, there is no error.

[byara]

Dear @OliverJAsh the error you are referring to is thrown from @babel/parser which we use to get the AST and all the imports and relevant information regarding the file. Basically the code has an issue according to @babel/parser (you can see it here). The plugin has no opinion about your code.

[OliverJAsh]

I don't think this would be an issue if the plugin parsed the AST using TypeScript rather than Babel.

[OliverJAsh]

Actually, shouldn't the plugin use the same parser specified via Prettier's --parser option?