Fix issue with casts from floating point to integer not truncating

- Fix issue where casting floats to integers was not handled properly so it would not truncate floats and instead was rounding them.

Assets/UdonSharp/Editor/UdonSharpExpressionCapture.cs

@@ -524,10 +524,28 @@ public SymbolDefinition CastSymbolToType(SymbolDefinition sourceSymbol, System.T
 
             if (conversionFunction != null && (isExplicit || isNumericCastValid))
             {
+                SymbolDefinition sourceNumericSymbol = sourceSymbol;
+
+                // System.Convert.ToIntXX with a floating point argument will not be truncated, instead it will be rounded using Banker's Rounding.
+                // This is not what we want for casts, so we first floor the input before running the conversion
+                if (UdonSharpUtils.IsFloatType(sourceSymbol.symbolCsType) && UdonSharpUtils.IsIntegerType(targetType))
+                {
+                    // Mathf.Floor only works on floats so if it's a double we need to convert it first.
+                    // This does lose a small amount of accuracy on gigantic numbers, but it should hopefully be enough until Udon has dedicated cast instructions at some point in the future
+                    SymbolDefinition inputFloat = CastSymbolToType(sourceSymbol, typeof(float), true);
+                    conversionFunction = UdonSharpUtils.GetNumericConversionMethod(targetType, typeof(float));
+
+                    using (ExpressionCaptureScope floatFloorMethodCaptureScope = new ExpressionCaptureScope(visitorContext, null))
+                    {
+                        floatFloorMethodCaptureScope.SetToMethods(new[] { typeof(Mathf).GetMethod("Floor", BindingFlags.Static | BindingFlags.Public) });
+                        sourceNumericSymbol = floatFloorMethodCaptureScope.Invoke(new SymbolDefinition[] { inputFloat });
+                    }
+                }
+
                 // This code is copied 3 times, todo: find a decent way to refactor it
                 SymbolDefinition castOutput = visitorContext.topTable.CreateUnnamedSymbol(targetType, SymbolDeclTypeFlags.Internal);
 
-                visitorContext.uasmBuilder.AddPush(sourceSymbol);
+                visitorContext.uasmBuilder.AddPush(sourceNumericSymbol);
                 visitorContext.uasmBuilder.AddPush(castOutput);
                 visitorContext.uasmBuilder.AddExternCall(visitorContext.resolverContext.GetUdonMethodName(conversionFunction));
 

Assets/UdonSharp/Editor/UdonSharpUtils.cs

@@ -103,6 +103,25 @@ public static bool HasModifier(this SyntaxTokenList syntaxTokens, string modifie
             typeof(long),
         };
 
+        private static readonly HashSet<System.Type> integerTypes = new HashSet<System.Type>()
+        {
+            typeof(byte),
+            typeof(sbyte),
+            typeof(short),
+            typeof(ushort),
+            typeof(int),
+            typeof(uint),
+            typeof(long),
+            typeof(ulong),
+        };
+
+        private static readonly HashSet<System.Type> floatTypes = new HashSet<System.Type>()
+        {
+            typeof(float),
+            typeof(double),
+            typeof(decimal),
+        };
+
         public static bool IsSignedType(System.Type type)
         {
             return signedTypes.Contains(type);
@@ -113,6 +132,16 @@ public static bool IsUnsignedType(System.Type type)
             return unsignedTypes.Contains(type);
         }
 
+        public static bool IsIntegerType(System.Type type)
+        {
+            return integerTypes.Contains(type);
+        }
+
+        public static bool IsFloatType(System.Type type)
+        {
+            return floatTypes.Contains(type);
+        }
+
         public static bool IsNumericType(System.Type type)
         {
             return implicitBuiltinConversions.ContainsKey(type);