error[E0428]: the name `Foo` is defined multiple times
  --> $DIR/duplicated_struct.rs:10:5
   |
7  |     pub struct Foo;
   |     --------------- previous definition of the type `Foo` here
...
10 |     pub struct Foo;
   |     ^^^^^^^^^^^^^^^ `Foo` redefined here
   |
   = note: `Foo` must be defined only once in the type namespace of this module