error[E0282]: type annotations needed for `B<T>`
  --> $DIR/issue-17551.rs:6:15
   |
LL |     let foo = B(marker::PhantomData);
   |         ---   ^ cannot infer type for `T`
   |         |
   |         consider giving `foo` the explicit type `B<T>`, where the type parameter `T` is specified

error: aborting due to previous error

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