`export import` of types is not allowed in namespaces when using `erasableSyntaxOnly`

🔎 Search Terms

export import alias type-only namespaces erasableSyntaxOnly

🕗 Version & Regression Information

• I was unable to test this on prior versions because erasableSyntaxOnly was just released

⏯ Playground Link

https://www.typescriptlang.org/play/?erasableSyntaxOnly=true&ts=5.8.2#code/PTAEBcAsEsGdQO4HsBOBrWBYAUAOwIYC2AprAA74DGxEAnmaaAN46ijEAeZq4oAJsUoAbfChrh6NAGJIkbALygAjDgC+OHCFAAjAK68ocfklK4A5L2ToANKHxCoSXQHNIoaODPwJDALRJcIVpbcFkcAhJyKnFJWAB1D0gAJWJObhReFmw2NJ53QnTeABVQRR9GNQ1sLUN4IyQ0fFpwolIKalAAN3tdRiycrjzKANheADNZUuVK7Bxyuyny2AA6GSQ5yVAORdiEqBTcjOWi1dkgA

💻 Code

// this works
namespace types {
  export declare type Foo  = 1
}

// but this doesn't work, although it's type-only, too
namespace typesWithReexport {
  export import T = types 
}

// ignoring the error, generally these should be both accessible
type a = types.Foo
type x = typesWithReexport.T.Foo

🙁 Actual behavior

export import re-exporting a namespace (or namespace member) of a type-only namespace from another type-only namespace results in This syntax is not allowed when 'erasableSyntaxOnly' is enabled.

🙂 Expected behavior

It should not error.

Additional information about the issue

@jakebailey asked me to open an issue to track this on bsky: https://bsky.app/profile/jakebailey.dev/post/3ljdc3ou7oc2w

从使用 erasableSyntaxOnly 的链接 TypeScript Playground 复现开始，并比较被接受的 export declare type 命名空间与被拒绝的 export import 再导出。跟踪命名空间示例的编译器诊断，并确定相关的 erasable syntax 检查。示例不再报告该错误，同时保留预期的仅类型命名空间访问，即表示完成。