rust-analyzer hangs with too many `#[test_case]`s

**rust-analyzer version**: master

**code snippet to reproduce**: 
```rust
#[test_case]
#[test_case]
#[test_case]
#[test_case]
#[test_case]
#[test_case]
#[test_case]
#[test_case]
fn test() {}
```
rust-analyzer will hang while trying to analyze this file. I think it's exponential, so if it doesn't for you, just add more `#[test_case]` :) 