relational_pattern_operator_return_type_not_assignable_to_bool

The return type of operators used in relational patterns must be assignable to 'bool'.

The analyzer produces this diagnostic when a relational pattern references an operator that doesn't produce a value of type bool.

The following code produces this diagnostic because the operator >, used in the relational pattern > c2, returns a value of type int rather than a bool:

class C {
  const C();
​
  int operator >(C c) => 3;
​
  bool operator <(C c) => false;
}
​
const C c2 = C();
​
void f(C c1) {
  if (c1 case > c2) {}
}

If there's a different operator that should be used, then change the operator:

class C {
  const C();
​
  int operator >(C c) => 3;
​
  bool operator <(C c) => false;
}
​
const C c2 = C();
​
void f(C c1) {
  if (c1 case < c2) {}
}

If the operator is expected to return bool, then update the declaration of the operator:

class C {
  const C();
​
  bool operator >(C c) => true;
​
  bool operator <(C c) => false;
}
​
const C c2 = C();
​
void f(C c1) {
  if (c1 case > c2) {}
}