warning: trait-associated function `from_iter` will become ambiguous in Rust 2021
  --> $DIR/generic-type-collision.rs:15:5
   |
LL |     <Vec<i32>>::from_iter(None);
   |     ^^^^^^^^^^^^^^^^^^^^^ help: disambiguate the associated function: `<Vec<i32> as MyTrait<_>>::from_iter`
   |
note: the lint level is defined here
  --> $DIR/generic-type-collision.rs:4:9
   |
LL | #![warn(rust_2021_prelude_collisions)]
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
   = note: for more information, see issue #85684 <https://github.com/rust-lang/rust/issues/85684>

warning: 1 warning emitted