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+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 */ }
+}
+```