54597ba11f
Suggest replacing `typeof(...)` with an actual type
This PR adds suggestion to replace `typeof(...)` with an actual type of `...`, for example in case of `typeof(1)` we suggest replacing it with `i32`.
If the expression
1. Is not const (`{ let a = 1; let _: typeof(a); }`)
2. Can't be found (`let _: typeof(this_variable_does_not_exist)`)
3. Or has non-suggestable type (closure, generator, error, etc)
we don't suggest anything.
The 1 one is sad, but it's not clear how to support non-consts expressions for `typeof`.
_This PR is inspired by [this tweet]._
[this tweet]: https://twitter.com/compiler_errors/status/1511945354752638976
For high-level intro to how type checking works in rustc, see the type checking chapter of the rustc dev guide.