error[E0531]: cannot find tuple struct or tuple variant `x` in this scope
  --> $DIR/issue-5927.rs:3:9
   |
LL |         x(1) => x(1)
   |         ^ not found in this scope

error[E0425]: cannot find function `x` in this scope
  --> $DIR/issue-5927.rs:3:17
   |
LL |         x(1) => x(1)
   |                 ^ not found in this scope

error: aborting due to 2 previous errors

Some errors have detailed explanations: E0425, E0531.
For more information about an error, try `rustc --explain E0425`.
