private MethodDefinition OverrideGetHashCode(
TypeDefinition caseClassTypeDefinition,
IEnumerable <CaseClassProperty> properties,
FieldVarietyDetector fieldVarietyDetector)
{
var method = new MethodDefinition(
nameof(GetHashCode),
MethodAttributes.Public | MethodAttributes.HideBySig | MethodAttributes.Virtual,
_typeSystem.Int32Reference);
var getHashCodeMethod = _moduleDefinition.ImportReference(
_typeSystem.ObjectDefinition.Methods.Single(x => x.Name == nameof(GetHashCode)));
var getHashCodeOfValueTypeMethod = _moduleDefinition.ImportReference(
_findType(typeof(ValueType).FullName).Methods.Single(m => m.Name == nameof(GetHashCode)));
var codeEmitter = method.Body.GetILProcessor();
codeEmitter.Emit(OpCodes.Ldc_I4, 857327845);
foreach (var property in properties)
{
codeEmitter.Emit(OpCodes.Ldc_I4, -1521134295);
codeEmitter.Emit(OpCodes.Mul);
var doAddition = Instruction.Create(OpCodes.Add);
if (fieldVarietyDetector.Detect(property.BackingFieldReference.FieldType).IsReferenceType ?? true)
{
var callGetHashCode = Instruction.Create(OpCodes.Callvirt, getHashCodeMethod);
property.BoxFieldValue(codeEmitter);
codeEmitter.Emit(OpCodes.Dup);
codeEmitter.Emit(OpCodes.Brtrue_S, callGetHashCode);
codeEmitter.Emit(OpCodes.Pop);
codeEmitter.Emit(OpCodes.Ldc_I4_0);
codeEmitter.Emit(OpCodes.Br_S, doAddition);
codeEmitter.Append(callGetHashCode);
}
else
{
codeEmitter.Emit(OpCodes.Ldarg_0);
codeEmitter.Emit(OpCodes.Ldfld, property.BackingFieldReference);
codeEmitter.Emit(OpCodes.Call, getHashCodeOfValueTypeMethod);
}
codeEmitter.Append(doAddition);
}
codeEmitter.Emit(OpCodes.Ret);
return(method);
}
public void EmitEqualityCheck(ILProcessor compareCodeEmitter, FieldVarietyDetector fieldVarietyDetector)
{
switch (fieldVarietyDetector.Detect(BackingFieldReference.FieldType))
{
case ReferenceTypeImplementingIEquatable referenceTypeImplementingIEquatable:
EmitFieldEqualityTestingCode(
compareCodeEmitter,
nameof(DeepEqualityComparer.EquatableReferencesAreEqual),
referenceTypeImplementingIEquatable.FieldType);
break;
case TypedCollection typedCollection:
EmitFieldEqualityTestingCode(
compareCodeEmitter,
nameof(DeepEqualityComparer.TypedCollectionsAreEqual),
typedCollection.ElementType);
break;
case UntypedColection _:
EmitFieldEqualityTestingCode(
compareCodeEmitter,
nameof(DeepEqualityComparer.UntypedCollectionsAreEqual));
break;
case PlainReferenceType plainReferenceType:
EmitFieldEqualityTestingCode(
compareCodeEmitter,
nameof(DeepEqualityComparer.ReferenceInstancesAreEqual),
plainReferenceType.FieldType);
break;
case ValueTypeImplementingIEquatable valueTypeImplementingIEquatable:
EmitFieldEqualityTestingCode(
compareCodeEmitter,
nameof(DeepEqualityComparer.EquatableValuesAreEqual),
valueTypeImplementingIEquatable.FieldType);
break;
case PlainValueType plainValueType:
EmitFieldEqualityTestingCode(
compareCodeEmitter,
nameof(DeepEqualityComparer.ValueInstancesAreEqual),
plainValueType.FieldType);
break;
case NullableTypeImplementingIEquatable nullableTypeImplementingIEquatable:
EmitFieldEqualityTestingCode(
compareCodeEmitter,
nameof(DeepEqualityComparer.EquatableNullablesAreEqual),
nullableTypeImplementingIEquatable.UnderlyingType);
break;
case PlainNullableType plainNullableType:
EmitFieldEqualityTestingCode(
compareCodeEmitter,
nameof(DeepEqualityComparer.NullablesAreEqual),
plainNullableType.UnderlyingType);
break;
case GenericTypeImplementingIEquatable genericTypeImplementingIEquatable:
EmitFieldEqualityTestingCode(
compareCodeEmitter,
nameof(DeepEqualityComparer.EquatableGenericsAreEqual),
genericTypeImplementingIEquatable.GenericParameter);
break;
case PlainGenericType plainGenericType:
EmitFieldEqualityTestingCode(
compareCodeEmitter,
nameof(DeepEqualityComparer.GenericsAreEqual),
plainGenericType.GenericParameter);
break;
case FieldVariety fieldVariety:
throw new InvalidOperationException($"Program logic exception: no code to handle {fieldVariety.GetType()} field variety.");
}
}