Allow attributing a function to specify that its return value is a pa…

…cked array.

Safety check return statements within functions to ensure that packed arrays are not returned as normal arrays or vice versa.

JSIL/ILBlockTranslator.cs

@@ -439,7 +439,7 @@ protected JSExpression Translate_ConstructorReplacement (
             return newExpression;
         }
 
-        protected JSExpression Translate_MethodReplacement (
+        protected JSExpression DoMethodReplacement (
             JSMethod method, JSExpression thisExpression, 
             JSExpression[] arguments, bool @virtual, bool @static, bool explicitThis
         ) {
@@ -582,6 +582,8 @@ protected JSExpression Translate_MethodReplacement (
                     result = JSInvocationExpression.InvokeMethod(method.Reference.DeclaringType, method, thisExpression, arguments);
             }
 
+            result = PackedArrayUtil.FilterInvocationResult(method.Method, result, TypeSystem);
+
             return result;
         }
 
@@ -1722,9 +1724,11 @@ protected JSContinueExpression Translate_LoopContinue (ILExpression node) {
 
         protected JSReturnExpression Translate_Ret (ILExpression node) {
             if (node.Arguments.FirstOrDefault() != null) {
-                return new JSReturnExpression(
-                    TranslateNode(node.Arguments[0])
-                );
+                var returnValue = TranslateNode(node.Arguments[0]);
+
+                PackedArrayUtil.CheckReturnValue(TypeInfo.Get(ThisMethodReference) as Internal.MethodInfo, returnValue, TypeSystem);
+
+                return new JSReturnExpression(returnValue);
             } else if (node.Arguments.Count == 0) {
                 return new JSReturnExpression();
             } else {
@@ -2905,7 +2909,7 @@ protected JSExpression Translate_Call (ILExpression node, MethodReference method
                 thisExpression = new JSNullExpression();
             }
 
-            var result = Translate_MethodReplacement(
+            var result = DoMethodReplacement(
                 new JSMethod(method, methodInfo, MethodTypes), 
                 thisExpression, arguments, false, 
                 !method.HasThis, explicitThis || methodInfo.IsConstructor
@@ -2975,7 +2979,7 @@ protected JSExpression Translate_Callvirt (ILExpression node, MethodReference me
                 );
             }
 
-            var result = Translate_MethodReplacement(
+            var result = DoMethodReplacement(
                new JSMethod(method, methodInfo, MethodTypes), 
                thisExpression, translatedArguments, true, 
                false, explicitThis

JSIL/PackedStructArray.cs

@@ -93,5 +93,43 @@ public static string[] GetPackedArrayArgumentNames (MethodInfo method, out TypeR
 
             return null;
         }
+
+        public static JSExpression FilterInvocationResult (MethodInfo method, JSExpression result, TypeSystem typeSystem) {
+            if (method == null)
+                return result;
+
+            var resultType = result.GetActualType(typeSystem);
+            var resultIsPackedArray = PackedArrayUtil.IsPackedArrayType(resultType);
+            var returnValueAttribute = method.Metadata.GetAttribute("JSIL.Meta.JSPackedArrayReturnValueAttribute");
+
+            if (returnValueAttribute != null) {
+                if (!resultIsPackedArray)
+                    return JSChangeTypeExpression.New(result, PackedArrayUtil.MakePackedArrayType(resultType, returnValueAttribute.Entries.First().Type), typeSystem);
+            }
+
+            return result;
+        }
+
+        public static void CheckReturnValue (MethodInfo method, JSExpression returnValue, TypeSystem typeSystem) {
+            if (method == null)
+                return;
+
+            var resultType = returnValue.GetActualType(typeSystem);
+            var resultIsPackedArray = PackedArrayUtil.IsPackedArrayType(resultType);
+
+            var returnValueAttribute = method.Metadata.GetAttribute("JSIL.Meta.JSPackedArrayReturnValueAttribute");
+            if (returnValueAttribute != null) {
+                if (!resultIsPackedArray)
+                    throw new ArgumentException(
+                        "Return value of method '" + method.Name + "' must be a packed array."
+                    );
+            } else {
+                if (resultIsPackedArray)
+                    throw new ArgumentException(
+                        "Return value of method '" + method.Name + "' is a packed array. " + 
+                        "For this to be valid you must attach a JSPackedArrayReturnValueAttribute to the method."
+                    );
+            }
+        }
     }
 }

Meta/Attributes.cs

@@ -183,6 +183,14 @@ public JSPackedArrayArgumentsAttribute (params string[] argumentNames) {
         }
     }
 
+    /// <summary>
+    /// Specifies that JSIL should represent the function's return value as a packed array.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Method)]
+    [JSIL.Runtime.LinkedType(typeof(JSIL.Runtime.IPackedArray<>))]
+    public class JSPackedArrayReturnValueAttribute : Attribute {
+    }
+
     [AttributeUsage(AttributeTargets.Method)]
     public class JSAllowPackedArrayArgumentsAttribute : Attribute {
     }

Tests/FailingTestCases/ReturnNormalArrayAsPackedArray.cs

@@ -0,0 +1,27 @@
+using System;
+using JSIL.Meta;
+
+public struct IntFloatPair {
+    public int Int;
+    public float Float;
+
+    public override string ToString () {
+        return String.Format("Int={0:0000}, Float={1:000.000}", Int, Float);
+    }
+}
+
+public static class Program {
+    public static IntFloatPair[] PackedArray = new IntFloatPair[2];
+
+    public static unsafe void Main (string[] args) {
+        var pa = ReturnPackedArray();
+
+        foreach (var item in pa)
+            Console.WriteLine(item);
+    }
+
+    [JSPackedArrayReturnValue]
+    public static IntFloatPair[] ReturnPackedArray () {
+        return PackedArray;
+    }
+}

Tests/FailingTestCases/ReturnPackedArrayAsNormalArray.cs

@@ -0,0 +1,27 @@
+using System;
+using JSIL.Meta;
+
+public struct IntFloatPair {
+    public int Int;
+    public float Float;
+
+    public override string ToString () {
+        return String.Format("Int={0:0000}, Float={1:000.000}", Int, Float);
+    }
+}
+
+public static class Program {
+    [JSPackedArray]
+    public static IntFloatPair[] PackedArray = new IntFloatPair[2];
+
+    public static unsafe void Main (string[] args) {
+        var pa = ReturnPackedArray();
+
+        foreach (var item in pa)
+            Console.WriteLine(item);
+    }
+
+    public static IntFloatPair[] ReturnPackedArray () {
+        return PackedArray;
+    }
+}

Tests/Tests.csproj

@@ -342,6 +342,8 @@
     <None Include="SimpleTestCases\StringFormatCustomPlacesNegative.cs" />
     <None Include="FailingTestCases\PassPackedArrayAsNormalArrayArgument.cs" />
     <None Include="FailingTestCases\PassNormalArrayAsPackedArrayArgument.cs" />
+    <None Include="FailingTestCases\ReturnNormalArrayAsPackedArray.cs" />
+    <None Include="FailingTestCases\ReturnPackedArrayAsNormalArray.cs" />
     <Compile Include="GenericTestFixture.cs" />
     <None Include="SimpleTestCases\GenericCreateInstance.cs" />
     <None Include="SimpleTestCases\GenericSelfConstraint.cs" />