TS2300

Duplicate identifier

Duplicate identifier 'Result'.

The compiler’s own words. Not translated — this is the string you pasted into a search box.

The same non-mergeable type name was declared twice in one scope.

Reproduction

type Result = { ok: true }

type Result = { ok: false }

The build asserts this emits exactly this code.

Why the compiler says this

Type aliases name one definition and do not declaration-merge. Two aliases with the same name leave every use ambiguous about which definition it means, so the duplicate is rejected at both declarations.

Fixes

01
```
type Result = { ok: true } | { ok: false }
```
Combine alternatives in one alias when they represent branches of the same concept.

type Success = { ok: true }
type Failure = { ok: false }

type Result = Success | Failure

Give distinct concepts distinct names, then compose them where needed.

Takeaway

Type aliases do not merge. Rename, remove, or deliberately compose duplicate definitions.

Where to go next

Type aliases Try it in the Lab

Errors