error[E0053]: method `call` has an incompatible type for trait --> $DIR/issue-20225.rs:6:3 | LL | impl<'a, T> Fn<(&'a T,)> for Foo { | - this type parameter LL | extern "rust-call" fn call(&self, (_,): (T,)) {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `&T`, found type parameter `T` | = note: expected fn pointer `extern "rust-call" fn(&Foo, (&'a T,))` found fn pointer `extern "rust-call" fn(&Foo, (T,))` error[E0053]: method `call_mut` has an incompatible type for trait --> $DIR/issue-20225.rs:11:3 | LL | impl<'a, T> FnMut<(&'a T,)> for Foo { | - this type parameter LL | extern "rust-call" fn call_mut(&mut self, (_,): (T,)) {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `&T`, found type parameter `T` | = note: expected fn pointer `extern "rust-call" fn(&mut Foo, (&'a T,))` found fn pointer `extern "rust-call" fn(&mut Foo, (T,))` error[E0053]: method `call_once` has an incompatible type for trait --> $DIR/issue-20225.rs:18:3 | LL | impl<'a, T> FnOnce<(&'a T,)> for Foo { | - this type parameter ... LL | extern "rust-call" fn call_once(self, (_,): (T,)) {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `&T`, found type parameter `T` | = note: expected fn pointer `extern "rust-call" fn(Foo, (&'a T,))` found fn pointer `extern "rust-call" fn(Foo, (T,))` error: aborting due to 3 previous errors For more information about this error, try `rustc --explain E0053`.