---
source: crates/biome_js_analyze/tests/spec_tests.rs
expression: invalidInterface.ts
---
# Input
```ts
interface I {
    f(): I
    g(i: I): void
}

export {};

```

# Diagnostics
```
invalidInterface.ts:1:11 lint/correctness/noUnusedVariables ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! This interface is unused.
  
  > 1 │ interface I {
      │           ^
    2 │     f(): I
    3 │     g(i: I): void
  
  i Unused variables usually are result of incomplete refactoring, typos and other source of bugs.
  

```