`withSignature` replies on the string representation of internal classes in the

javac implementation. Those string representations are not necessarily stable

across versions of javac, and they can change when a method is annotated with

type-use annotations.

Additionally, `withSignature` currently has at least one undocumented behavioral

quirk.

The most reasonable use case for `withSignature` is for methods that declare or

use type variables, which are difficult or impossible to express with the rest

of the `MethodMatchers` API. Still, where practical, prefer to write your own

matching code instead of using `withSignature`.