error[E0282]: type annotations needed
  --> $DIR/issue-17551.rs:6:15
   |
LL |     let foo = B(marker::PhantomData); //~ ERROR type annotations needed
   |         ---   ^ cannot infer type for `T`
   |         |
   |         consider giving `foo` a type

error: aborting due to previous error

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