perf: IsError is now a computed property

This change saves us 8 bits in the ErrorOr<TValue> struct which leads to less execution time when an instance is copied by value. As the struct is now properly encapsulated from a Design by Contract point of view, I simply choose _errors being null as the indicator for errors not being present. Signed-off-by: Kenny Pflug <kenny.pflug@live.de>
amantinband · May 9, 2024 · d534d0e · d534d0e
1 parent a76df26
commit d534d0e
Showing 1 changed file with 84 additions and 87 deletions.
diff --git a/src/ErrorOr/ErrorOr.cs b/src/ErrorOr/ErrorOr.cs
@@ -1,87 +1,84 @@
-using System.Diagnostics.CodeAnalysis;
-
-namespace ErrorOr;
-
-/// <summary>
-/// A discriminated union of errors or a value.
-/// </summary>
-/// <typeparam name="TValue">The type of the underlying <see cref="Value"/>.</typeparam>
-public readonly partial record struct ErrorOr<TValue> : IErrorOr<TValue>
-{
-    private readonly TValue? _value = default;
-    private readonly List<Error>? _errors = null;
-
-    /// <summary>
-    /// Prevents a default <see cref="ErrorOr"/> struct from being created.
-    /// </summary>
-    public ErrorOr()
-    {
-        throw new InvalidOperationException("Default construction of ErrorOr<TValue> is invalid. Please use provided factory methods to instantiate.");
-    }
-
-    private ErrorOr(Error error)
-    {
-        _errors = [error];
-        IsError = true;
-    }
-
-    private ErrorOr(List<Error> errors)
-    {
-        _errors = errors;
-        IsError = true;
-    }
-
-    private ErrorOr(TValue value)
-    {
-        _value = value;
-        IsError = false;
-    }
-
-    /// <summary>
-    /// Gets a value indicating whether the state is error.
-    /// </summary>
-    [MemberNotNullWhen(true, nameof(_errors))]
-    [MemberNotNullWhen(true, nameof(Errors))]
-    [MemberNotNullWhen(false, nameof(Value))]
-    [MemberNotNullWhen(false, nameof(_value))]
-    public bool IsError { get; }
-
-    /// <summary>
-    /// Gets the list of errors. If the state is not error, the list will contain a single error representing the state.
-    /// </summary>
-    public List<Error> Errors => IsError ? _errors! : throw new InvalidOperationException("The Errors property cannot be accessed when no errors have been recorded. Check IsError before accessing Errors.");
-
-    /// <summary>
-    /// Gets the list of errors. If the state is not error, the list will be empty.
-    /// </summary>
-    public List<Error> ErrorsOrEmptyList => IsError ? _errors! : [];
-
-    /// <summary>
-    /// Gets the value.
-    /// </summary>
-    public TValue Value => _value!;
-
-    /// <summary>
-    /// Gets the first error.
-    /// </summary>
-    public Error FirstError
-    {
-        get
-        {
-            if (!IsError)
-            {
-                throw new InvalidOperationException("The FirstError property cannot be accessed when no errors have been recorded. Check IsError before accessing FirstError.");
-            }
-
-            return _errors![0];
-        }
-    }
-
-    /// <summary>
-    /// Creates an <see cref="ErrorOr{TValue}"/> from a list of errors.
-    /// </summary>
-    public static ErrorOr<TValue> From(List<Error> errors)
-    {
-        return errors;
-    }
-}
+using System.Diagnostics.CodeAnalysis;
+
+namespace ErrorOr;
+
+/// <summary>
+/// A discriminated union of errors or a value.
+/// </summary>
+/// <typeparam name="TValue">The type of the underlying <see cref="Value"/>.</typeparam>
+public readonly partial record struct ErrorOr<TValue> : IErrorOr<TValue>
+{
+    private readonly TValue? _value = default;
+    private readonly List<Error>? _errors = null;
+
+    /// <summary>
+    /// Prevents a default <see cref="ErrorOr"/> struct from being created.
+    /// </summary>
+    public ErrorOr()
+    {
+        throw new InvalidOperationException("Default construction of ErrorOr<TValue> is invalid. Please use provided factory methods to instantiate.");
+    }
+
+    private ErrorOr(Error error)
+    {
+        _errors = [error];
+    }
+
+    private ErrorOr(List<Error> errors)
+    {
+        _errors = errors;
+    }
+
+    private ErrorOr(TValue value)
+    {
+        _value = value;
+    }
+
+    /// <summary>
+    /// Gets a value indicating whether the state is error.
+    /// </summary>
+    [MemberNotNullWhen(true, nameof(_errors))]
+    [MemberNotNullWhen(true, nameof(Errors))]
+    [MemberNotNullWhen(false, nameof(Value))]
+    [MemberNotNullWhen(false, nameof(_value))]
+    public bool IsError => _errors is not null;
+
+    /// <summary>
+    /// Gets the list of errors. If the state is not error, the list will contain a single error representing the state.
+    /// </summary>
+    public List<Error> Errors => IsError ? _errors! : throw new InvalidOperationException("The Errors property cannot be accessed when no errors have been recorded. Check IsError before accessing Errors.");
+
+    /// <summary>
+    /// Gets the list of errors. If the state is not error, the list will be empty.
+    /// </summary>
+    public List<Error> ErrorsOrEmptyList => IsError ? _errors! : [];
+
+    /// <summary>
+    /// Gets the value.
+    /// </summary>
+    public TValue Value => _value!;
+
+    /// <summary>
+    /// Gets the first error.
+    /// </summary>
+    public Error FirstError
+    {
+        get
+        {
+            if (!IsError)
+            {
+                throw new InvalidOperationException("The FirstError property cannot be accessed when no errors have been recorded. Check IsError before accessing FirstError.");
+            }
+
+            return _errors![0];
+        }
+    }
+
+    /// <summary>
+    /// Creates an <see cref="ErrorOr{TValue}"/> from a list of errors.
+    /// </summary>
+    public static ErrorOr<TValue> From(List<Error> errors)
+    {
+        return errors;
+    }
+}