microsoft / microsoft/TypeScript

Confusing missing property error in a circular situation

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@ahejlsberg y travaille déjà.

Depuis le 18/9/2026.

Domain: Mapped Types Help Wanted Possible Improvement
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Description

### 🔎 Search Terms

missing property mapped type getter deferred

### 🕗 Version & Regression Information

- This is the behavior in every version I tried

### ⏯ Playground Link

https://www.typescriptlang.org/play/?ts=6.0.0-dev.20250802#code/JYOwLgpgTgZghgYwgAgFoHsAmAVAngBwgB5sA+ZAbwChll18xh0Q4AbALmQCIwoBXCF2QAfbvFYBnQQG4adPmHwLO2WQF8qVUJFiIUGTAGVeoAObIIAD0ghMEtFjyEiEkyFPlqteo2ZtOXOJSXOqaYAT6WIYAFnCEyAC8yABKEAjoUJgubqYANMhwILiksuHxAApQEGCMMLgk5EkUyADaANLIoMgA1hC46DDI2AC6Ku3DyGrIAGSUaqURyACSIDDQAPIARgBWaWBOxDFxKFY2dg5GsYSNyJXVtfVyXrSt3Z0gPX0DyEfxcPa-CAtboTU4QWz2Zo+JgsDjcXgCIQaF4vAD8PTkKM4IAgADdoMNUZxAcDhi0uOgFEowFxhrJaFNZs9aMD3p9+oNAQUAVcgSCLNZwecoQwYf54fxBJNMWjkDj8VAZbROCDibzSeTKYoFLT6dKSlpwNB4EgLltdggwCQBWd7AZAeQwRCLgciCs1lBzXtXWRPHJoX44YE2MFQoadCbIph1qLA9anecDK7CsVSHIE3bHBESJqqTqJqI+LYIDBQBBMH7vLHYQEETIqBoqJg0qw4FVkDAi5aYXQdnt44LnfbeaQABQSXkqACUnAMXstDVkzYQrfbnZA3eYyFcUDMo5nF2Mu-cS5bbZQ683HwDsIHtpd2ZTpDHEgQ0QgAFs4NPZ1gY75bzIWQqHSEBXGQABhOBIFMDJcESXsLTAUdnhYD8IE4Hc9ynXI5FMapkHwc9wH3SgZSqMA+Cga9qzYUcoJguCpz1NRcLUZjNCsfAMjAZBQPArVqQQhiIFgqBcAAOkEhRZCAA

### 💻 Code

```ts
interface ZodType {
optional: "true" | "false";
output: T;
}

interface ZodString extends ZodType {
optional: "false";
}

type ZodShape = Record;
type Prettify = { [K in keyof T]: T[K] } & {};
type InferObjectType = Prettify<
{
[k in keyof Shape as Shape[k] extends { optional: "true" }
? k
: never]?: Shape[k]["output"];
} & {
[k in keyof Shape as Shape[k] extends { optional: "true" }
? never
: k]: Shape[k]["output"];
}
>;
interface ZodObject extends ZodType> {
optional: "false";
}

interface ZodOptional>
extends ZodType {
optional: "true";
}

declare function object(shape: T): ZodObject;
declare function string(): ZodString;
declare function optional>(schema: T): ZodOptional;

const Category = object({
name: string(),
get parent() {
// Argument of type 'ZodObject<{ name: ZodString; readonly parent: ZodOptional>; }>' is not assignable to parameter of type 'ZodType'.
// Property 'output' is missing in type 'ZodObject<{ name: ZodString; readonly parent: ZodOptional>; }>' but required in type 'ZodType'.(2345)
return optional(Category);
},
});

export const output = Category.output;
```

### 🙁 Actual behavior

A very confusing error is produced here. A `ZodObject` extends `ZodType` and that has an `output` property so how it can be missing?

### 🙂 Expected behavior

I don't expect to see this error

### Additional information about the issue

Note that if we remove `export const output = Category.output;` then we can see a new error appearing:
> 'parent' implicitly has return type 'any' because it does not have a return type annotation and is referenced directly or indirectly in one of its return expressions.(7023)

And this one makes sense (but I'd argue the other one shouldn't appear at all in this scenario).

This has changed with https://github.com/microsoft/TypeScript/pull/58337 , before this PR the circularity error was present with and without `export const output = Category.output;`

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