E0646: include_str!("./error_codes/E0646.md"),
E0647: include_str!("./error_codes/E0647.md"),
E0648: include_str!("./error_codes/E0648.md"),
+E0657: include_str!("./error_codes/E0657.md"),
E0658: include_str!("./error_codes/E0658.md"),
E0659: include_str!("./error_codes/E0659.md"),
E0660: include_str!("./error_codes/E0660.md"),
// used in argument position
E0640, // infer outlives requirements
// E0645, // trait aliases not finished
- E0657, // `impl Trait` can only capture lifetimes bound at the fn level
E0667, // `impl Trait` in projections
E0687, // in-band lifetimes cannot be used in `fn`/`Fn` syntax
E0688, // in-band lifetimes cannot be mixed with explicit lifetime binders
--- /dev/null
+A lifetime bound on a trait implementation was captured at an incorrect place.
+
+Erroneous code example:
+
+```compile_fail,E0657
+trait Id<T> {}
+trait Lt<'a> {}
+
+impl<'a> Lt<'a> for () {}
+impl<T> Id<T> for T {}
+
+fn free_fn_capture_hrtb_in_impl_trait()
+ -> Box<for<'a> Id<impl Lt<'a>>> // error!
+{
+ Box::new(())
+}
+
+struct Foo;
+impl Foo {
+ fn impl_fn_capture_hrtb_in_impl_trait()
+ -> Box<for<'a> Id<impl Lt<'a>>> // error!
+ {
+ Box::new(())
+ }
+}
+```
+
+Here, you have used the inappropriate lifetime in the `impl Trait`,
+The `impl Trait` can only capture lifetimes bound at the fn or impl
+level.
+
+To fix this we have to define the lifetime at the function or impl
+level and use that lifetime in the `impl Trait`. For example you can
+define the lifetime at the function:
+
+```
+trait Id<T> {}
+trait Lt<'a> {}
+
+impl<'a> Lt<'a> for () {}
+impl<T> Id<T> for T {}
+
+fn free_fn_capture_hrtb_in_impl_trait<'b>()
+ -> Box<for<'a> Id<impl Lt<'b>>> // ok!
+{
+ Box::new(())
+}
+
+struct Foo;
+impl Foo {
+ fn impl_fn_capture_hrtb_in_impl_trait<'b>()
+ -> Box<for<'a> Id<impl Lt<'b>>> // ok!
+ {
+ Box::new(())
+ }
+}
+```
error: aborting due to 2 previous errors
+For more information about this error, try `rustc --explain E0657`.