error[E0308]: `match` arms have incompatible types
  --> $DIR/issue-101465.rs:20:18
   |
LL | /     match true {
LL | |         true => B,
   | |                 - this is found to be of type `B`
LL | |         false => C,
   | |                  ^ expected `B`, found `C`
LL | |
LL | |     }
   | |_____- `match` arms have incompatible types
   |
help: you could change the return type to be a boxed trait object
   |
LL | fn foo() -> Box<dyn Tr> {
   |             ~~~~~~~   +
help: if you change the return type to expect trait objects, box the returned expressions
   |
LL ~         true => Box::new(B),
LL ~         false => Box::new(C),
   |

error: aborting due to previous error

For more information about this error, try `rustc --explain E0308`.