error[E0308]: mismatched types --> $DIR/issue-2951.rs:3:10 | LL | fn foo(x: T, y: U) { | - - found type parameter | | | expected type parameter LL | let mut xx = x; | - expected due to this value LL | xx = y; | ^ expected type parameter `T`, found type parameter `U` | = note: expected type parameter `T` found type parameter `U` = note: a type parameter was expected, but a different one was found; you might be missing a type parameter or trait bound = note: for more information, visit https://doc.rust-lang.org/book/ch10-02-traits.html#traits-as-parameters error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0308`.