Null propagation playground

gistfile1.cs

convert "Null-conditional invocation" {
  if (x != null) { // also 'cond && x != null'
    x.M();
  }
} into {
  x?.M();
}

convert "Null-conditional invocation (inverted)" {
  if (x == null) return _;
  x.M();
  return _; // can be implicit/void
} into {
  x?.M();
  return _;
}

convert "Null-conditional value return" {
  if (x != null) {
    return x.M();
  }
  return null; // maybe much upper
} into {
  return x?.M();
}

convert "Null-conditional value return (inverted)" {
  if (x == null) return null;
  return x.M();
} into {
  return x?.M();
}

convert "Null-conditional value retur (with else)" {
  if (x != null) {
    return x.M();
  } else {
    return null;
  }
} into {
  return x?.M();
}

convert "Null-conditional value return (inverted with else)" {
  if (x == null) {
    return null;
  } else {
    return x.M();
  }
} into {
  return x?.M();
}

convert "Null-conditional navigation" {
  if (x != null) {
    x.F();
    x = x.M();
  }
} into {
  x?.F();
  x = x?.M();
}

convert "Type-conditional invocation" {
  if (x is T) {
    ((T) x).M();
  }
} into {
  (x as T)?.M();
}

convert "Type-conditional invocation (inverted)" {
  if (!(x is T) return _;
  ((T) x).M();
  return _; // can be implicit/void
} into {
  (x as T)?.M();
  return _;
}

convert "Nested if statements" {
  if (x != null) { // also 'cond && x != null'
    var y = x.M(); // optional
    if (y != null && ...) { }
  }
} into {
  var y = x?.M();
  if (y != null && ...) { }
}

convert "Merge sequential checks" {
  if (x == null) return _; // also goto/continue/break
  var y = x.M();
  if (y == null) return _; // also goto/continue/break
} into {
  var y = x?.M();
  if (y == null) return _;
}


// TODO: THINK ABOUT else { } everywhere






if (liftedStatement == null) return null;

return liftedStatement;