error[E0005]: refutable pattern in local binding: `Bar` and `Baz` not covered
  --> $DIR/issue-31561.rs:8:9
   |
LL |     let Thing::Foo(y) = Thing::Foo(1);
   |         ^^^^^^^^^^^^^ patterns `Bar` and `Baz` not covered
   |
   = note: `let` bindings require an "irrefutable pattern", like a `struct` or an `enum` with only one variant
   = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html
note: `Thing` defined here
  --> $DIR/issue-31561.rs:3:5
   |
LL | enum Thing {
   |      -----
LL |     Foo(u8),
LL |     Bar,
   |     ^^^ not covered
LL |     Baz
   |     ^^^ not covered
   = note: the matched value is of type `Thing`
help: you might want to use `if let` to ignore the variants that aren't matched
   |
LL |     let y = if let Thing::Foo(y) = Thing::Foo(1) { y } else { todo!() };
   |     ++++++++++                                   ++++++++++++++++++++++
help: alternatively, on nightly, you might want to use `#![feature(let_else)]` to handle the variants that aren't matched
   |
LL |     let Thing::Foo(y) = Thing::Foo(1) else { todo!() };
   |                                       ++++++++++++++++

error: aborting due to previous error

For more information about this error, try `rustc --explain E0005`.