Add more docs

src/Rascal/Error.cs

@@ -24,6 +24,7 @@ public static implicit operator Error(string message) =>
 /// <param name="message">The message to display.</param>
 public sealed class StringError(string message) : Error
 {
+    /// <inheritdoc/>
     public override string Message => message;
 
     /// <summary>
@@ -38,6 +39,9 @@ public sealed class StringError(string message) : Error
 /// <param name="exception">The exception in the error.</param>
 public sealed class ExceptionError(Exception exception) : Error
 {
+    /// <summary>
+    /// The exception in the error.
+    /// </summary>
     public Exception Exception { get; } = exception;
 
     /// <summary>
@@ -57,6 +61,7 @@ public sealed class AggregateError(IEnumerable<Error> errors) : Error
     /// </summary>
     public IReadOnlyCollection<Error> Errors { get; } = errors.ToList();
 
+    /// <inheritdoc/>
     public override string Message => string.Join("\n", Errors.Select(x => x.Message));
 }
 
@@ -66,6 +71,7 @@ public sealed class AggregateError(IEnumerable<Error> errors) : Error
 /// <param name="message">A message which describes the thing which wasn't found.</param>
 public sealed class NotFoundError(string message) : Error
 {
+    /// <inheritdoc/>
     public override string Message => message;
 }
 
@@ -75,6 +81,7 @@ public sealed class NotFoundError(string message) : Error
 /// <param name="message">An optional message describing the operation and why it is invalid.</param>
 public sealed class InvalidOperationError(string? message = null) : Error
 {
+    /// <inheritdoc/>
     public override string Message => message ?? "Invalid operation.";
 }
 
@@ -84,6 +91,7 @@ public sealed class InvalidOperationError(string? message = null) : Error
 /// <param name="message">An optional message describing the thing which is <see langword="null"/>.</param>
 public sealed class NullError(string? message = null) : Error
 {
+    /// <inheritdoc/>
     public override string Message => message ?? "Value is null.";
 }
 
@@ -99,6 +107,7 @@ public sealed class ValidationError(string message, object? source) : Error
     /// </summary>
     public object? Source => source;
 
+    /// <inheritdoc/>
     public override string Message => message;
 }
 
@@ -114,6 +123,7 @@ public sealed class ParseError(string message, object? source) : Error
     /// </summary>
     public object? Source => source;
 
+    /// <inheritdoc/>
     public override string Message => message;
 }
 
@@ -123,5 +133,6 @@ public sealed class ParseError(string message, object? source) : Error
 /// <param name="message">The optional message describing the task cancellation.</param>
 public sealed class CancellationError(string? message = null) : Error
 {
+    /// <inheritdoc/>
     public override string Message => message ?? "Task was cancelled.";
 }

src/Rascal/Result.cs

@@ -41,6 +41,9 @@ public Result(Error error)
         this.error = error;
     }
 
+    /// <summary>
+    /// Gets a string representation of the result.
+    /// </summary>
     [Pure]
     public override string ToString() =>
         HasValue

src/Rascal/ResultExtensions.cs

@@ -100,6 +100,7 @@ public static Result<IReadOnlyList<T>> Sequence<T>(this IEnumerable<Result<T>> r
     /// <typeparam name="TValue">The type of values in the  dictionary.</typeparam>
     /// <param name="dict">The dictionary to try locate the key in.</param>
     /// <param name="key">The key to locate.</param>
+    /// <param name="error">The error to return if the key is not present.</param>
     /// <returns>A result containing the value associated with <paramref name="key"/> in the dictionary,
     /// or an error if the key is not present.</returns>
     public static Result<TValue> TryGetValueR<TKey, TValue>(
@@ -118,6 +119,7 @@ public static Result<TValue> TryGetValueR<TKey, TValue>(
     /// <typeparam name="T">The type of the elements in the list.</typeparam>
     /// <param name="list">The list to index.</param>
     /// <param name="index">The zero-based index of the element to get.</param>
+    /// <param name="error">The error to return if the index is out of range.</param>
     /// <returns>A result containing the value at <paramref name="index"/> in the list,
     /// or an error if the index is out of range of the list.</returns>
     public static Result<T> Index<T>(this IReadOnlyList<T> list, int index, Error? error = null) =>

src/Rascal/Result_Equality.cs

@@ -9,38 +9,74 @@ namespace Rascal;
     System.Numerics.IEqualityOperators<Result<T>, T, bool>
 #endif
 {
+    /// <summary>
+    /// Checks whether the result has a value and the value is equal to another value.
+    /// </summary>
+    /// <param name="other">The value to check for equality with the value in the result.</param>
     [Pure]
     public bool Equals(T? other) =>
         HasValue && (other?.Equals(value) ?? value is null);
 
+    /// <summary>
+    /// Checks whether the result is equal to another result.
+    /// Results are equal if both results have values which are equal,
+    /// or if both results are errors.
+    /// </summary>
+    /// <param name="other">The result to check for equality with the current result.</param>
     [Pure]
     public bool Equals(Result<T> other) =>
         HasValue && other.HasValue && (other.value?.Equals(value) ?? value is null) ||
         !HasValue && !other.HasValue;
 
+    /// <inheritdoc/>
     [Pure]
     public override bool Equals(object? other) =>
         other is T x && Equals(x) ||
         other is Result<T> r && Equals(r);
 
+    /// <inheritdoc/>
     [Pure]
     public override int GetHashCode() =>
         HasValue
             ? value?.GetHashCode() ?? 0
             : 0;
 
+    /// <summary>
+    /// Checks whether two results are equal.
+    /// Results are equal if both results have values which are equal,
+    /// or if both results are errors.
+    /// </summary>
+    /// <param name="a">The first result to compare.</param>
+    /// <param name="b">The second result to compare.</param>
     [Pure]
     public static bool operator ==(Result<T> a, Result<T> b) =>
         a.Equals(b);
 
+    /// <summary>
+    /// Checks whether two results are not equal.
+    /// Results are equal if both results have values which are equal,
+    /// or if both results are errors.
+    /// </summary>
+    /// <param name="a">The first result to compare.</param>
+    /// <param name="b">The second result to compare.</param>
     [Pure]
     public static bool operator !=(Result<T> a, Result<T> b) =>
         !a.Equals(b);
 
+    /// <summary>
+    /// Checks whether a result has a value and the value is equal to another value.
+    /// </summary>
+    /// <param name="a">The result to compare.</param>
+    /// <param name="b">The value to check for equality with the value in the result.</param>
     [Pure]
     public static bool operator ==(Result<T> a, T? b) =>
         a.Equals(b);
-
+
+    /// <summary>
+    /// Checks whether a result either does not have a value, or the value is not equal to another value.
+    /// </summary>
+    /// <param name="a">The result to compare.</param>
+    /// <param name="b">The value to check for inequality with the value in the result.</param>
     [Pure]
     public static bool operator !=(Result<T> a, T? b) =>
         !a.Equals(b);

src/Rascal/Result_Mapping.cs

@@ -49,6 +49,7 @@ public Result<TNew> SelectMany<TNew>(Func<T, Result<TNew>> mapping) =>
     /// The expression <c>r.SelectMany(x => f(x), (x, y) => g(x, y))</c> can be written as
     /// <c>r.Bind(x => f(x).Map(y => g(x, y)))</c>.
     /// </remarks>
+    /// <param name="other">The function used to map the value to an intermediate result.</param>
     /// <param name="mapping">The function used to map the value to a new result.</param>
     /// <typeparam name="TOther">The type of the intermediate value.</typeparam>
     /// <typeparam name="TNew">The type of the new value.</typeparam>

src/Rascal/Result_Matching.cs

@@ -140,7 +140,7 @@ public T GetValueOrDefault(T @default) =>
     /// Gets the value within the result,
     /// or a default value if the result does not contain a value.
     /// </summary>
-    /// <param name="default">A function to get a default value to return
+    /// <param name="getDefault">A function to get a default value to return
     /// if the result does not contain a value.</param>
     [Pure]
     public T GetValueOrDefault(Func<T> getDefault) =>

src/Rascal/Result_Utility.cs

@@ -51,6 +51,7 @@ public Result<TDerived> ToType<TDerived>(string? error = null)
                     value))
             : new(Error);
 
+#if NETCOREAPP
     /// <summary>
     /// Checks whether the value in the result matches a predicate,
     /// and if not replaces the value with an error.
@@ -65,12 +66,23 @@ public Result<TDerived> ToType<TDerived>(string? error = null)
     /// error produced by <paramref name="getError"/>.
     /// If the original result does not contain a value, that result will be returned.</returns>
     [Pure]
-#if NETCOREAPP
     public Result<T> Validate(
         Func<T, bool> predicate,
         Func<T, Error>? getError = null,
         [CallerArgumentExpression(nameof(predicate))] string expr = "") =>
 #else
+    /// <summary>
+    /// Checks whether the value in the result matches a predicate,
+    /// and if not replaces the value with an error.
+    /// </summary>
+    /// <param name="predicate">The predicate to match the value against.</param>
+    /// <param name="getError">A function to produce an error
+    /// if the value doesn't match the predicate.</param>
+    /// <returns>A result which contains the value of the original result
+    /// if the value matches <paramref name="predicate"/>, otherwise an
+    /// error produced by <paramref name="getError"/>.
+    /// If the original result does not contain a value, that result will be returned.</returns>
+    [Pure]
     public Result<T> Validate(
         Func<T, bool> predicate,
         Func<T, Error>? getError = null) =>
@@ -86,6 +98,7 @@ public Result<T> Validate(
 #endif
             : new(Error);
 
+#if NETCOREAPP
     /// <summary>
     /// Checks whether the value in the result matches a predicate,
     /// and if not replaces the value with an error.
@@ -98,13 +111,22 @@ public Result<T> Validate(
     /// If the original result does not contain a value, that result will be returned.</returns>
     [Pure]
     public Result<T> Where(
-#if NETCOREAPP
         Func<T, bool> predicate,
         [CallerArgumentExpression(nameof(predicate))] string expr = "") =>
         Validate(predicate, null, expr);
 #else
+    /// <summary>
+    /// Checks whether the value in the result matches a predicate,
+    /// and if not replaces the value with an error.
+    /// </summary>
+    /// <param name="predicate">The predicate to match the value against.</param>
+    /// <returns>A result which contains the value of the original result
+    /// if the value matches <paramref name="predicate"/>, otherwise an error.
+    /// If the original result does not contain a value, that result will be returned.</returns>
+    [Pure]
+    public Result<T> Where(
         Func<T, bool> predicate) =>
-        Validate(predicate, null);
+        Validate(predicate);
 #endif
 
     /// <summary>