error[E0599]: no method named `f` found for unit type `()` in the current scope
  --> $DIR/shadowed-trait-methods.rs:13:8
   |
LL |     pub trait T { fn f(&self) {} }
   |                      - the method is available for `()` here
...
LL |     ().f()
   |        ^ method not found in `()`
   |
   = help: items from traits can only be used if the trait is in scope
help: the following trait is implemented but not in scope; perhaps add a `use` for it:
   |
LL + use foo::T;
   |

error: aborting due to previous error

For more information about this error, try `rustc --explain E0599`.