Babel's TypeScript support doesn't match the compiler w.r.t. inline declarations of in-scope identifiers

[ELLIOTTCABLE]

Bug Report

Current Behavior
When encountering a declare statement for an identifier that's already in scope, Babel throws up. The upstream TypeScript compiler understands this syntax.

{ SyntaxError: /Users/ec/Sync/Code/excmd/src/interface.ts: Identifier 'Something'
    has already been declared (3:14)

   1 | import Something from './somewhere.js'
   2 | 
>  3 | declare class Something {
     |               ^
   4 |    // ...
   5 | }
    at Object.raise (/Users/ec/Sync/Code/excmd/node_modules/@babel/parser/lib/index.js:6325:17)
    at TypeScriptScopeHandler.checkRedeclarationInScope (/Users/ec/Sync/Code/excmd/node_modules/@babel/parser/lib/index.js:3759:12)
    at TypeScriptScopeHandler.declareName (/Users/ec/Sync/Code/excmd/node_modules/@babel/parser/lib/index.js:3725:12)
    at TypeScriptScopeHandler.declareName (/Users/ec/Sync/Code/excmd/node_modules/@babel/parser/lib/index.js:3835:11)
    at Object.checkLVal (/Users/ec/Sync/Code/excmd/node_modules/@babel/parser/lib/index.js:8021:22)
    at Object.checkLVal (/Users/ec/Sync/Code/excmd/node_modules/@babel/parser/lib/index.js:5727:15)
    at Object.parseClassId (/Users/ec/Sync/Code/excmd/node_modules/@babel/parser/lib/index.js:10855:14)
    at Object.parseClassId (/Users/ec/Sync/Code/excmd/node_modules/@babel/parser/lib/index.js:5508:11)
    at Object.parseClass (/Users/ec/Sync/Code/excmd/node_modules/@babel/parser/lib/index.js:10572:10)
    at Object.tsTryParseDeclare (/Users/ec/Sync/Code/excmd/node_modules/@babel/parser/lib/index.js:4984:21)
  pos: 1216,
  loc: Position { line: 3, column: 14 },
  code: 'BABEL_PARSE_ERROR' }

Input Code

import Something from './somewhere.js'

declare class Something {
   // ...
}

Expected behavior/code
As with tsc, this should have no effect on the produced code; these declarations are essentially "inline .d.ts" for non-TypeScript imports. To satisfy the current Babel, I guess I'll need to extract these declarations into additional .d.ts files, and check those into my source-control; but as I only have a single TypeScript file in my codebase, I'd really prefer to keep the typings for other modules centralized to that single TypeScript file!

Babel Configuration (.babelrc, package.json, cli command)

// .babelrc
{
   "presets": ["@babel/env", "@babel/preset-typescript"]
}

// CLI invocation
babel --verbose src --extensions '.ts,.js' --ignore '**/*.bs.js' --ignore '**/*.d.ts' --copy-files --out-dir lib

Environment

• Babel version(s): 7.5.5 (@babel/core 7.5.5)
• Node/npm version: v10.12.0
• OS: macOS 10.14.5
• How you are using Babel: cli

Additional context/Screenshots
The above example is somewhat massaged / simplified from my actual codebase I can't even get the web-playground (with "TypeScript" enabled!) to parse a simple declare class Blah, but I would have included a working example if I could.

[ELLIOTTCABLE]

• Vaguely relevant: typescript transform confused about types and values with the same name #7943
• Link to TypeScript playground for above simplified example-code (note that it's properly parsed, and the type-error is then understood);
• Link to Babel playground, with my attempt to replicate the above. Unfortunately, I'm getting completely unrelated syntax-errors that I don't see locally, not sure why, instead of the actual redeclaration-error I'm reporting here.

[babel-bot]

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[nicolo-ribaudo]

Probably fixed by #10352

[ELLIOTTCABLE]

I had high hopes, @nicolo-ribaudo, but unfortunately, it doesn't look like #10352 resolved this particular problem! )=

With babel --version #=> 7.8.3 (@babel/core 7.8.3),

import * as $_AST from 'bs-excmd/src/aST.bs'

declare class $_AST {
   static copy_expression($expr: $Expressiont): $Expressiont
   static get_literal_exn($sub: $or_subexpr): $string
   static get_sub_exn($sub: $or_subexpr): $Expressiont
   // ...

I'm still getting:

$ babel --root-mode upward --verbose src --extensions '.ts,.js' --ignore '**/*.d.ts' --copy-files --out-dir lib
TypeError: Duplicate declaration "$_AST"
  66 | type $element = Nominal<object, 'MenhirInterpreter.element'>
  67 | 
> 68 | declare class $_AST {
     |               ^^^^^
  69 |    static copy_expression($expr: $Expressiont): $Expressiont
  70 |    // FIXME: this is a lieeeee
  71 |    static get_literal_exn($sub: $or_subexpr): $string
    at File.buildCodeFrameError (/Users/ec/Sync/Code/excmd/node_modules/@babel/core/lib/transformation/file/file.js:267:12)
    at Scope.checkBlockScopedCollisions (/Users/ec/Sync/Code/excmd/node_modules/@babel/core/node_modules/@babel/traverse/lib/scope/index.js:306:22)
    at Scope.registerBinding (/Users/ec/Sync/Code/excmd/node_modules/@babel/core/node_modules/@babel/traverse/lib/scope/index.js:459:16)
    at Scope.registerDeclaration (/Users/ec/Sync/Code/excmd/node_modules/@babel/core/node_modules/@babel/traverse/lib/scope/index.js:406:12)
    at Object.BlockScoped (/Users/ec/Sync/Code/excmd/node_modules/@babel/core/node_modules/@babel/traverse/lib/scope/index.js:149:28)
    at Object.newFn (/Users/ec/Sync/Code/excmd/node_modules/@babel/core/node_modules/@babel/traverse/lib/visitors.js:220:17)
    at NodePath._call (/Users/ec/Sync/Code/excmd/node_modules/@babel/core/node_modules/@babel/traverse/lib/path/context.js:55:20)
    at NodePath.call (/Users/ec/Sync/Code/excmd/node_modules/@babel/core/node_modules/@babel/traverse/lib/path/context.js:38:14)
    at NodePath.visit (/Users/ec/Sync/Code/excmd/node_modules/@babel/core/node_modules/@babel/traverse/lib/path/context.js:90:31)
    at TraversalContext.visitQueue (/Users/ec/Sync/Code/excmd/node_modules/@babel/core/node_modules/@babel/traverse/lib/context.js:112:16)

[nicolo-ribaudo]

It fixed it for the parser but not in @babel/traverse

[ELLIOTTCABLE]

Ahhhh, I see. Just to be sure: the non-registration fix should affect this combination of an ES6 module-star-import and a class-type-declaration?

Should I open a separate Issue somewhere else? 😣 I took a look at your changes, and dug around checkBlockScopedCollisions in hopes that perhaps I could correspondingly update @babel/traverse to match, but it doesn't look like that module handles TypeScript specially at all, so I'm a little afraid to dive in and try to add the first TypeScript-specific hack in there! 🤣

[nicolo-ribaudo]

Well, when we introduce a big new feature like TS it will inevitably sneak across all the core modules 🤷‍♂️ 😛

[liuxingbaoyu]

Can't reproduce in latest version, seems to have been fixed.