typeof with identically named type and value causes invalid .d.ts output

[ssalbdivad]

🔎 Search Terms

type, value, .d.ts, circular, circularity, invalid, output, declaration

🕗 Version & Regression Information

• This changed between versions 5.4 and 5.5

⏯ Playground Link

https://www.typescriptlang.org/play/?ts=5.5.0-dev.20240501#code/KYDwDg9gTgLgBAYwgOwM7wCbFQqBLMGPFVOAXjgG8AoOOAMwggC44AiAIwEMo3qBfatVCRYcGAE8wwOFhz5CxNOXFTgEerOy4CREkA

💻 Code

export const descriptions = {
  foo: "bar"
}

export type descriptions = typeof descriptions

🙁 Actual behavior

Actual .d.ts output:

export declare const descriptions: typeof descriptions;
export type descriptions = typeof descriptions;

🙂 Expected behavior

Expected .d.ts output:

export declare const descriptions: {
    foo: string;
};
export type descriptions = typeof descriptions;

Additional information about the issue

No response

[Andarist]

Bisects to #57772

[ssalbdivad]

@RyanCavanaugh Is this not worth patching into TS 5.5?

Given how easy this is to repro, I'd assume this would occur often in the wild.

Issues like this that are only exposed in build output are also particularly insidious because most library authors don't explicitly check their build output, and most consumers use skipLibCheck, which would result in the affected type silently resolving to any.

[patroza]

This would be quite a disaster especially considering this only occurs in the .d.ts which for libraries are often generated just before publishing.

[mikearnaldi]

Following as Effect may be affected

[mikearnaldi]

Given that this was introduced before release wouldn't it be a better strategy to revert the commit that introduced the bug and defer that commit to 5.6? It feels a bit odd to introduce a bug, recognize that it is a bug and defer the fix till a further version. I would understand the choice if this didn't came up pre-release

[datner]

Hmm this matches a ton of common behavior, even the humble as const "enum" is affected.

export const Color = {
  Red: "Red",
  Green: "Green",
  Blue: "Blue"
} as const

export type Color = typeof Color
export type Colors = Color[keyof Color]

This being broked^
though this works fine:

export const Color = {
  Red: "Red",
  Green: "Green",
  Blue: "Blue"
} as const

export type Color = typeof Color[keyof typeof Color]

hmmmm

[RyanCavanaugh]

Yeah, good points all around