---
source: crates/biome_js_analyze/tests/spec_tests.rs
expression: infer_incorrect.ts
---
# Input
```ts
type A = number extends infer T ? never : T;

```

# Diagnostics
```
infer_incorrect.ts:1:43 lint/correctness/noUndeclaredVariables ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! The T variable is undeclared
  
  > 1 │ type A = number extends infer T ? never : T;
      │                                           ^
    2 │ 
  

```