error: unexpected `self` parameter in function
  --> $DIR/error-recovery-mismatch.rs:11:29
   |
LL |     fn fold<T>(&self, _: T, &self._) {}
   |                             ^^^^^ must be the first parameter of an associated function

error: expected one of `)` or `,`, found `.`
  --> $DIR/error-recovery-mismatch.rs:11:34
   |
LL |     fn fold<T>(&self, _: T, &self._) {}
   |                                  ^
   |                                  |
   |                                  expected one of `)` or `,`
   |                                  help: missing `,`

error[E0415]: identifier `self` is bound more than once in this parameter list
  --> $DIR/error-recovery-mismatch.rs:11:30
   |
LL |     fn fold<T>(&self, _: T, &self._) {}
   |                              ^^^^ used as parameter more than once

warning: anonymous parameters are deprecated and will be removed in the next edition
  --> $DIR/error-recovery-mismatch.rs:11:35
   |
LL |     fn fold<T>(&self, _: T, &self._) {}
   |                                   ^ help: try naming the parameter or explicitly ignoring it: `_: _`
   |
   = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2018!
   = note: for more information, see issue #41686 <https://github.com/rust-lang/rust/issues/41686>
   = note: `#[warn(anonymous_parameters)]` on by default

error[E0121]: the placeholder `_` is not allowed within types on item signatures for functions
  --> $DIR/error-recovery-mismatch.rs:11:35
   |
LL |     fn fold<T>(&self, _: T, &self._) {}
   |                                   ^ not allowed in type signatures
   |
help: use type parameters instead
   |
LL -     fn fold<T>(&self, _: T, &self._) {}
LL +     fn fold<T, U>(&self, _: T, &self.U) {}
   |

error: aborting due to 4 previous errors; 1 warning emitted

Some errors have detailed explanations: E0121, E0415.
For more information about an error, try `rustc --explain E0121`.