error[E0382]: use of moved value: `a`
  --> $DIR/issue-31287-drop-in-guard.rs:7:9
   |
LL |     let a = Some("...".to_owned());
   |         - move occurs because `a` has type `Option<String>`, which does not implement the `Copy` trait
LL |     let b = match a {
LL |         Some(_) if { drop(a); false } => None,
   |                           - value moved here
LL |         x => x,
   |         ^ value used here after move
   |
help: consider cloning the value if the performance cost is acceptable
   |
LL |         Some(_) if { drop(a.clone()); false } => None,
   |                            ++++++++

error[E0382]: use of moved value: `a`
  --> $DIR/issue-31287-drop-in-guard.rs:13:9
   |
LL |     let a = Some("...".to_owned());
   |         - move occurs because `a` has type `Option<String>`, which does not implement the `Copy` trait
LL |     let b = match a {
LL |         Some(_) if let Some(()) = { drop(a); None } => None,
   |                                          - value moved here
LL |         x => x,
   |         ^ value used here after move
   |
help: consider cloning the value if the performance cost is acceptable
   |
LL |         Some(_) if let Some(()) = { drop(a.clone()); None } => None,
   |                                           ++++++++

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0382`.