error[E0128]: generic parameter defaults cannot reference parameters before they are declared
  --> $DIR/invalid-type-param-default.rs:12:12
   |
LL | fn mdn<T = T::Item>(_: T) {}
   |            ^^^^^^^ cannot reference `T` before it is declared

error: defaults for generic parameters are not allowed here
  --> $DIR/invalid-type-param-default.rs:7:8
   |
LL | fn avg<T = i32>(_: T) {}
   |        ^^^^^^^
   |
   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
   = note: for more information, see issue #36887 <https://github.com/rust-lang/rust/issues/36887>
   = note: `#[deny(invalid_type_param_default)]` (part of `#[deny(future_incompatible)]`) on by default

error: defaults for generic parameters are not allowed here
  --> $DIR/invalid-type-param-default.rs:12:8
   |
LL | fn mdn<T = T::Item>(_: T) {}
   |        ^^^^^^^^^^^
   |
   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
   = note: for more information, see issue #36887 <https://github.com/rust-lang/rust/issues/36887>

error: defaults for generic parameters are not allowed here
  --> $DIR/invalid-type-param-default.rs:18:6
   |
LL | impl<T = i32> S<T> {}
   |      ^^^^^^^
   |
   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
   = note: for more information, see issue #36887 <https://github.com/rust-lang/rust/issues/36887>

error: aborting due to 4 previous errors

For more information about this error, try `rustc --explain E0128`.
Future incompatibility report: Future breakage diagnostic:
error: defaults for generic parameters are not allowed here
  --> $DIR/invalid-type-param-default.rs:7:8
   |
LL | fn avg<T = i32>(_: T) {}
   |        ^^^^^^^
   |
   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
   = note: for more information, see issue #36887 <https://github.com/rust-lang/rust/issues/36887>
   = note: `#[deny(invalid_type_param_default)]` (part of `#[deny(future_incompatible)]`) on by default

Future breakage diagnostic:
error: defaults for generic parameters are not allowed here
  --> $DIR/invalid-type-param-default.rs:12:8
   |
LL | fn mdn<T = T::Item>(_: T) {}
   |        ^^^^^^^^^^^
   |
   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
   = note: for more information, see issue #36887 <https://github.com/rust-lang/rust/issues/36887>
   = note: `#[deny(invalid_type_param_default)]` (part of `#[deny(future_incompatible)]`) on by default

Future breakage diagnostic:
error: defaults for generic parameters are not allowed here
  --> $DIR/invalid-type-param-default.rs:18:6
   |
LL | impl<T = i32> S<T> {}
   |      ^^^^^^^
   |
   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
   = note: for more information, see issue #36887 <https://github.com/rust-lang/rust/issues/36887>
   = note: `#[deny(invalid_type_param_default)]` (part of `#[deny(future_incompatible)]`) on by default