Trap Result

src/Function.cs

@@ -554,6 +554,20 @@ public static Function FromCallback<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11
         /// <returns>Returns true if the type signature of the function is valid or false if not.</returns>
         public bool CheckTypeSignature(Type? returnType = null, params Type[] parameters)
         {
+            // Check if the return type is Result<T>, Result, ResultWithBacktrace<T> or ResultWithBacktrace
+            if (returnType != null && returnType.IsResult())
+            {
+                // Try to get the type the result wraps (may be null if it's one of the non-generic result types)
+                var wrappedReturnType = returnType.IsGenericType ? returnType.GetGenericArguments()[0] : null;
+
+                // Check that the result does not attempt to wrap another result (e.g. Result<Result<int>>)
+                if (wrappedReturnType != null && wrappedReturnType.IsResult())
+                    return false;
+
+                // Type check with the wrapped value instead of the result
+                return CheckTypeSignature(wrappedReturnType, parameters);
+            }
+
             // Check if the func returns no values if that's expected
             if (Results.Count == 0 && returnType != null)
             {
@@ -2007,10 +2021,10 @@ private unsafe TR InvokeWithReturn<TR>(ReadOnlySpan<Value> arguments, IReturnTyp
 
             try
             {
-                Invoke(arguments, output);
+                var trap = Invoke(arguments, output);
 
                 // Note: null suppression is safe because `Invoke` checks that `store` is not null
-                return factory.Create(store!, output);
+                return factory.Create(store!, trap, output);
             }
             finally
             {
@@ -2037,7 +2051,11 @@ private unsafe void InvokeWithoutReturn(ReadOnlySpan<Value> arguments)
         {
             try
             {
-                Invoke(arguments, stackalloc Value[0]);
+                var trap = Invoke(arguments, stackalloc Value[0]);
+                if (trap != IntPtr.Zero)
+                {
+                    throw TrapException.FromOwnedTrap(trap);
+                }
             }
             finally
             {
@@ -2103,19 +2121,21 @@ private unsafe void InvokeWithoutReturn(ReadOnlySpan<Value> arguments)
                 throw new ArgumentNullException(nameof(store));
             }
 
-            var context = store.Context;
-
             // Convert arguments (ValueBox) into a form wasm can consume (Value)
             Span<Value> args = stackalloc Value[Parameters.Count];
-            for (int i = 0; i < arguments.Length; ++i)
+            for (var i = 0; i < arguments.Length; ++i)
                 args[i] = arguments[i].ToValue(Parameters[i]);
 
             // Make some space to store the return results
             Span<Value> resultsSpan = stackalloc Value[Results.Count];
 
             try
             {
-                Invoke(args, resultsSpan);
+                var trap = Invoke(args, resultsSpan);
+                if (trap != IntPtr.Zero)
+                {
+                    throw TrapException.FromOwnedTrap(trap);
+                }
 
                 if (Results.Count == 0)
                 {
@@ -2161,9 +2181,9 @@ private unsafe void InvokeWithoutReturn(ReadOnlySpan<Value> arguments)
         /// <param name="arguments">The arguments to pass to the function, wrapped as `Value`</param>
         /// <param name="resultsOut">Output span to store the results in, must be the correct length</param>
         /// <returns>
-        ///   Returns null if the function has no return value.
+        ///   Returns the trap ptr or zero
         /// </returns>
-        private unsafe void Invoke(ReadOnlySpan<Value> arguments, Span<Value> resultsOut)
+        private unsafe IntPtr Invoke(ReadOnlySpan<Value> arguments, Span<Value> resultsOut)
         {
             if (IsNull)
             {
@@ -2190,10 +2210,7 @@ private unsafe void Invoke(ReadOnlySpan<Value> arguments, Span<Value> resultsOut
                 throw WasmtimeException.FromOwnedError(error);
             }
 
-            if (trap != IntPtr.Zero)
-            {
-                throw TrapException.FromOwnedTrap(trap);
-            }
+            return trap;
         }
 
         Extern IExternal.AsExtern()

src/Result.cs

@@ -0,0 +1,270 @@
+using System;
+
+namespace Wasmtime
+{
+    /// <summary>
+    /// Indicates what type of result this is
+    /// </summary>
+    public enum ResultType
+    {
+        /// <summary>
+        /// Excecution succeeded
+        /// </summary>
+        Ok = 0,
+
+        /// <summary>
+        /// Result contains a trap
+        /// </summary>
+        Trap = 2,
+    }
+
+    /// <summary>
+    /// A result from a function call which may represent a Value or a Trap. If a trap happens the full backtrace is captured.
+    /// </summary>
+    public readonly struct ResultWithBacktrace
+    {
+        /// <summary>
+        /// Indicates what type of result this contains
+        /// </summary>
+        public ResultType Type { get; }
+
+        private readonly TrapException? _trap;
+
+        internal ResultWithBacktrace(IntPtr trap)
+        {
+            Type = ResultType.Trap;
+            _trap = TrapException.FromOwnedTrap(trap);
+        }
+
+        /// <summary>
+        /// Get the trap associated with this result
+        /// </summary>
+        /// <exception cref="InvalidOperationException">Thrown if this Type != Types.Trap</exception>
+        public TrapException Trap
+        {
+            get
+            {
+                if (Type != ResultType.Trap)
+                    throw new InvalidOperationException($"Cannot get 'Trap' from '{Type}' type result");
+                return _trap!;
+            }
+        }
+    }
+
+    /// <summary>
+    /// A result from a function call which may represent a Value or a Trap
+    /// </summary>
+    public readonly struct Result
+    {
+        /// <summary>
+        /// Indicates what type of result this contains
+        /// </summary>
+        public ResultType Type { get; }
+
+        private readonly TrapCode _trap;
+
+        internal Result(IntPtr trap)
+        {
+            Type = ResultType.Trap;
+            _trap = TrapException.GetTrapCode(trap);
+            TrapException.Native.wasm_trap_delete(trap);
+
+        }
+
+        /// <summary>
+        /// Get the trap associated with this result
+        /// </summary>
+        /// <exception cref="InvalidOperationException">Thrown if this Type != Types.Trap</exception>
+        public TrapCode Trap
+        {
+            get
+            {
+                if (Type != ResultType.Trap)
+                    throw new InvalidOperationException($"Cannot get 'Trap' from '{Type}' type result");
+                return _trap;
+            }
+        }
+    }
+
+    /// <summary>
+    /// A result from a function call which may represent a Value or a Trap. If a trap happens the full backtrace is captured.
+    /// </summary>
+    /// <typeparam name="T"></typeparam>
+    public readonly struct ResultWithBacktrace<T>
+    {
+        /// <summary>
+        /// Indicates what type of result this contains
+        /// </summary>
+        public ResultType Type { get; }
+
+        private readonly T? _value;
+        private readonly TrapException? _trap;
+
+        internal ResultWithBacktrace(T value)
+        {
+            Type = ResultType.Ok;
+            _value = value;
+            _trap = null;
+        }
+
+        internal ResultWithBacktrace(IntPtr trap)
+        {
+            Type = ResultType.Trap;
+            _value = default;
+            _trap = TrapException.FromOwnedTrap(trap);
+        }
+
+        /// <summary>
+        /// Convert this result into a value, throw if it is a Trap
+        /// </summary>
+        /// <param name="value"></param>
+        /// <returns></returns>
+        /// <exception cref="TrapException">Thrown if Type == Trap</exception>
+        /// <exception cref="ArgumentOutOfRangeException">Thrown if Type property contains an unknown value</exception>
+        public static explicit operator T?(ResultWithBacktrace<T> value)
+        {
+            switch (value.Type)
+            {
+                case ResultType.Ok:
+                    return value._value;
+
+                case ResultType.Trap:
+                    throw value._trap!;
+
+                default:
+                    throw new ArgumentOutOfRangeException(nameof(value), $"Unknown Result Type property value '{value.Type}'");
+            }
+        }
+
+        /// <summary>
+        /// Get the value associated with this result
+        /// </summary>
+        /// <exception cref="InvalidOperationException">Thrown if this Type != Types.Value</exception>
+        public T? Value
+        {
+            get
+            {
+                if (Type != ResultType.Ok)
+                    throw new InvalidOperationException($"Cannot get 'Value' from '{Type}' type result");
+                return _value;
+            }
+        }
+
+        /// <summary>
+        /// Get the trap associated with this result
+        /// </summary>
+        /// <exception cref="InvalidOperationException">Thrown if this Type != Types.Trap</exception>
+        public TrapException Trap
+        {
+            get
+            {
+                if (Type != ResultType.Trap)
+                    throw new InvalidOperationException($"Cannot get 'Trap' from '{Type}' type result");
+                return _trap!;
+            }
+        }
+    }
+
+    /// <summary>
+    /// A result from a function call which may represent a Value or a Trap
+    /// </summary>
+    /// <typeparam name="T"></typeparam>
+    public readonly struct Result<T>
+    {
+        /// <summary>
+        /// Indicates what type of result this contains
+        /// </summary>
+        public ResultType Type { get; }
+
+        private readonly T? _value;
+        private readonly TrapCode _trap;
+
+        internal Result(T value)
+        {
+            Type = ResultType.Ok;
+
+            _value = value;
+            _trap = default;
+        }
+
+        internal Result(IntPtr trap)
+        {
+            Type = ResultType.Trap;
+
+            _value = default;
+
+            _trap = TrapException.GetTrapCode(trap);
+            TrapException.Native.wasm_trap_delete(trap);
+
+        }
+
+        /// <summary>
+        /// Convert this result into a value, throw if it is a Trap
+        /// </summary>
+        /// <param name="value"></param>
+        /// <returns></returns>
+        /// <exception cref="TrapException">Thrown if Type == Trap</exception>
+        /// <exception cref="ArgumentOutOfRangeException">Thrown if Type property contains an unknoown value</exception>
+        public static explicit operator T?(Result<T> value)
+        {
+            switch (value.Type)
+            {
+                case ResultType.Ok:
+                    return value._value;
+
+                case ResultType.Trap:
+                    throw new TrapException($"{value._trap} trap", null, value._trap);
+
+                default:
+                    throw new ArgumentOutOfRangeException(nameof(value), $"Unknown Result Type property value '{value.Type}'");
+            }
+        }
+
+        /// <summary>
+        /// Get the value associated with this result
+        /// </summary>
+        /// <exception cref="InvalidOperationException">Thrown if this Type != Types.Value</exception>
+        public T? Value
+        {
+            get
+            {
+                if (Type != ResultType.Ok)
+                    throw new InvalidOperationException($"Cannot get 'Value' from '{Type}' type result");
+                return _value;
+            }
+        }
+
+        /// <summary>
+        /// Get the trap associated with this result
+        /// </summary>
+        /// <exception cref="InvalidOperationException">Thrown if this Type != Types.Trap</exception>
+        public TrapCode Trap
+        {
+            get
+            {
+                if (Type != ResultType.Trap)
+                    throw new InvalidOperationException($"Cannot get 'Trap' from '{Type}' type result");
+                return _trap;
+            }
+        }
+    }
+
+    internal static class TypeExtensions
+    {
+        internal static bool IsResult(this Type type)
+        {
+            if (type == typeof(Result) || type == typeof(ResultWithBacktrace))
+            {
+                return true;
+            }
+
+            if (!type.IsGenericType)
+            {
+                return false;
+            }
+
+            var gtd = type.GetGenericTypeDefinition();
+            return typeof(Result<>) == gtd || typeof(ResultWithBacktrace<>) == gtd;
+        }
+    }
+}