fill match arms for struct-like enum variant patterns introduce unused variables

Given an enum like:

enum Foo {
  A(X)
  B{y:Y,z:Z}
}

Fill match arms seems to

match foo {
  A(_) => todo!(),
  B{y, z} => todo!(),
}

The y's and z's, in my experience tend to produce a lot of unused variable warnings.
the alternative B{y:_y, z:_z} => todo!(), is very verbose and seems like adding stuff that will only need to be removed.

One option which seems like it might be viable is filling with B{..} => todo!(),
Eventually there could be an assist for "Fill structure fields for .."

Start by locating the match-arm fill assist entry point and its existing tests for enum patterns. Compare generated arms for tuple-like and struct-like variants, then make the result avoid unnecessary bindings while preserving complete pattern coverage; done means the relevant assist tests cover the proposed .. form without unused-variable warnings.