pattern_assignment_not_local_variable

Only local variables can be assigned in pattern assignments.

The analyzer produces this diagnostic when a pattern assignment assigns a value to anything other than a local variable. Patterns can't assign to fields or top-level variables.

If the code is cleaner when destructuring with a pattern, then rewrite the code to assign the value to a local variable in a pattern declaration, assigning the non-local variable separately:

class C {
  var x = 0;

  void f((int, int) r) {
    (x, _) = r;
  }
}

If the code is cleaner when using a pattern assignment, then rewrite the code to assign the value to a local variable, assigning the non-local variable separately:

class C {
  var x = 0;

  void f((int, int) r) {
    var (a, _) = r;
    x = a;
  }
}

If the code is cleaner without using a pattern assignment, then rewrite the code to not use a pattern assignment:

class C {
  var x = 0;

  void f((int, int) r) {
    x = r.$1;
  }
}

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