An identifier is bound more than once in a pattern.
Erroneous code example:
```compile_fail,E0416
match (1, 2) {
(x, x) => {} // error: identifier `x` is bound more than once in the
// same pattern
}
```
Please verify you didn't misspell identifiers' name. Example:
```
match (1, 2) {
(x, y) => {} // ok!
}
```
Or maybe did you mean to unify? Consider using a guard:
```
# let (A, B, C) = (1, 2, 3);
match (A, B, C) {
(x, x2, see) if x == x2 => { /* A and B are equal, do one thing */ }
(y, z, see) => { /* A and B unequal; do another thing */ }
}
```