error[E0282]: type annotations needed
  --> $DIR/unknown_type_for_closure.rs:2:13
   |
LL |     let x = |b: Vec<_>| {};
   |             ^^^^^^^^^^^^^^ cannot infer type for struct `Vec<_>`

error[E0282]: type annotations needed
  --> $DIR/unknown_type_for_closure.rs:6:14
   |
LL |     let x = |_| {};
   |              ^
   |
help: consider giving this closure parameter an explicit type
   |
LL |     let x = |_: /* Type */| {};
   |               ++++++++++++

error[E0282]: type annotations needed
  --> $DIR/unknown_type_for_closure.rs:10:14
   |
LL |     let x = |k: _| {};
   |              ^ cannot infer type

error[E0282]: type annotations needed
  --> $DIR/unknown_type_for_closure.rs:14:28
   |
LL |     let x = || -> Vec<_> { Vec::new() };
   |                            ^^^^^^^^ cannot infer type of the type parameter `T` declared on the struct `Vec`
   |
help: consider specifying the generic argument
   |
LL |     let x = || -> Vec<_> { Vec::<T>::new() };
   |                               +++++

error: aborting due to 4 previous errors

For more information about this error, try `rustc --explain E0282`.