[record_use] Dart API: Put non-const calls more front and center #2718

Iterable<CallReference> callsFor(Identifier id);

sealed class CallReference { ... }

// A direct call with arguments.
final class CallWithArguments extends CallReference {
  // ... properties for positional and named arguments
}

// A tear-off of the method.
final class CallTearOff extends CallReference { ... }

// A potential dynamic invocation.
final class DynamicInvocation extends CallReference { ... }

import 'package:record_use/record_use.dart';

// A simple Either type to represent success (Right) or failure (Left).
sealed class Either<L, R> {}

class Left<L, R> extends Either<L, R> {
  final L value;
  Left(this.value);
}

class Right<L, R> extends Either<L, R> {
  final R value;
  Right(this.value);
}

Either<List<String>, List<Constant>> processMethodUsages(
    Recordings recordings, Identifier methodId) {
  final calls = recordings.callsFor(methodId);
  final constValues = <Constant>[];
  final errors = <String>[];

  for (final call in calls) {
    switch (call) {
      case CallWithArguments(
          location: final loc,
          namedArguments: {'myArg': final Constant constArg}
        ):
        constValues.add(constArg);
        break;

      case CallTearOff(location: final loc):
        errors.add('Error: Found a tear-off at ${loc.uri}:${loc.line}.');
        break;

      case DynamicInvocation(location: final loc):
        errors.add('Error: Found a dynamic invocation at ${loc.uri}:${loc.line}.');
        break;

      case CallWithArguments(
          location: final loc,
          namedArguments: {'myArg': null}
        ):
        errors.add(
          'Error: Call at ${loc.uri}:${loc.line} had a non-constant \'myArg\'.',
        );
        break;

      case CallWithArguments(location: final loc):
        errors.add(
          'Error: Call at ${loc.uri}:${loc.line} did not provide the \'myArg\' argument.',
        );
        break;
    }
  }

  if (errors.isNotEmpty) {
    return Left(errors);
  }
  return Right(constValues);
}