error[E0116]: cannot define inherent `impl` for a type outside of the crate where the type is defined
  --> $DIR/no-attr-empty-impl.rs:4:1
   |
LL | impl extern_crate::StructWithAttr {}
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl for type defined outside of crate.
   |
   = note: define and implement a trait or new type instead

error[E0116]: cannot define inherent `impl` for a type outside of the crate where the type is defined
  --> $DIR/no-attr-empty-impl.rs:7:1
   |
LL | impl extern_crate::StructNoAttr {}
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl for type defined outside of crate.
   |
   = note: define and implement a trait or new type instead

error[E0116]: cannot define inherent `impl` for a type outside of the crate where the type is defined
  --> $DIR/no-attr-empty-impl.rs:10:1
   |
LL | impl extern_crate::EnumWithAttr {}
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl for type defined outside of crate.
   |
   = note: define and implement a trait or new type instead

error[E0116]: cannot define inherent `impl` for a type outside of the crate where the type is defined
  --> $DIR/no-attr-empty-impl.rs:13:1
   |
LL | impl extern_crate::EnumNoAttr {}
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl for type defined outside of crate.
   |
   = note: define and implement a trait or new type instead

error[E0390]: cannot define inherent `impl` for primitive types
  --> $DIR/no-attr-empty-impl.rs:16:6
   |
LL | impl f32 {}
   |      ^^^
   |
   = help: consider using an extension trait instead

error: aborting due to 5 previous errors

Some errors have detailed explanations: E0116, E0390.
For more information about an error, try `rustc --explain E0116`.