error[E0451]: field `x` of struct `a::Foo` is private
  --> $DIR/private-struct-field-pattern.rs:25:15
   |
LL |         Foo { x: _ } => {}  //~ ERROR field `x` of struct `a::Foo` is private
   |               ^^^^ field `x` is private

error: aborting due to previous error

For more information about this error, try `rustc --explain E0451`.