b71ef8a26e
This does a deeper removal of the `lint:` prefix by removing the `DiagnosticId::as_str` method and replacing it with `as_concise_str`. We remove the associated error type and simplify the `Display` impl for `DiagnosticId` as well. This turned out to catch a `lint:` that was still in the diagnostic output: the part that says why a lint is enabled.
Markdown files within the mdtest/ subdirectory are tests of type inference and type checking;
executed by the tests/mdtest.rs integration test.
See crates/ty_test/README.md for documentation of this test format.