60 lines
2.6 KiB
C#
60 lines
2.6 KiB
C#
using System.Reflection;
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namespace Just.Railway;
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internal static class ReflectionHelper
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{
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[Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
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public static R ObjectCast<R>(object value) where R: class => (R)value;
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[Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
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public static bool IsEqual<T>(T? left, T? right) => TypeReflectionCache<T>.IsEqualFunc(left, right);
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[Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
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/// <summary>
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/// Test for potential nullability
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/// </summary>
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/// <returns>true if T is reference type or Nullable value type.</returns>
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public static bool IsNullable<T>() => TypeReflectionCache<T>.IsNullable;
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[Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
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public static bool IsNullableStruct<T>() => TypeReflectionCache<T>.IsNullableStruct;
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private static class TypeReflectionCache<T>
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{
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public static readonly Func<T?, T?, bool> IsEqualFunc;
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static TypeReflectionCache()
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{
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var type = typeof(T);
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var isNullableStruct = type.IsGenericType && type.GetGenericTypeDefinition() == typeof(Nullable<>);
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var underlyingType = isNullableStruct ? type.GenericTypeArguments.First() : type;
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var thisType = typeof(TypeReflectionCache<T>);
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var equatableType = typeof(IEquatable<>).MakeGenericType(underlyingType);
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if (equatableType.IsAssignableFrom(underlyingType))
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{
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var isEqualFunc = thisType.GetMethod(isNullableStruct ? nameof(IsEqualNullable) : nameof(IsEqual), BindingFlags.Static | BindingFlags.Public)
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!.MakeGenericMethod(underlyingType);
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IsEqualFunc = (Func<T?, T?, bool>)Delegate.CreateDelegate(typeof(Func<T?, T?, bool>), isEqualFunc);
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}
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else
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{
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IsEqualFunc = static (left, right) => left is null ? right is null : left.Equals(right);
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}
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IsNullableStruct = isNullableStruct;
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IsNullable = isNullableStruct || !type.IsValueType;
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}
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public static bool IsNullable { get; }
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public static bool IsNullableStruct { get; }
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#pragma warning disable CS8604 // Possible null reference argument.
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[Pure] public static bool IsEqual<R>(R? left, R? right) where R : notnull, IEquatable<R>, T => left is null ? right is null : left.Equals(right);
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[Pure] public static bool IsEqualNullable<R>(R? left, R? right) where R : struct, IEquatable<R> => left is null ? right is null : right is not null && left.Value.Equals(right.Value);
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#pragma warning restore CS8604 // Possible null reference argument.
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}
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}
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