### What it does
Checks for trivial [regex](https://crates.io/crates/regex)
creation (with `Regex::new`, `RegexBuilder::new`, or `RegexSet::new`).

### Why is this bad?
Matching the regex can likely be replaced by `==` or
`str::starts_with`, `str::ends_with` or `std::contains` or other `str`
methods.

### Known problems
If the same regex is going to be applied to multiple
inputs, the precomputations done by `Regex` construction can give
significantly better performance than any of the `str`-based methods.

### Example
```
Regex::new("^foobar")
```