Correctly translating static method conversion expressions - fixes issue #20

Author: SteveWilkes

ReadableExpressions.UnitTests/WhenTranslatingConversions.cs

@@ -2,6 +2,7 @@
 {
     using System;
     using System.IO;
+    using NetStandardPolyfills;
 #if !NET35
     using System.Linq.Expressions;
     using Xunit;
@@ -86,5 +87,24 @@ public void ShouldTranslateAnUnboxExpression()
 
             translated.ShouldBe("((int)o)");
         }
+
+        // https://github.com/agileobjects/ReadableExpressions/issues/20
+        [Fact]
+        public void ShouldTranslateConversionWithCustomStaticMethod()
+        {
+            var stringParameter = Expression.Parameter(typeof(string), "str");
+            var targetType = typeof(int);
+
+            var body = Expression.Convert(
+                stringParameter,
+                targetType,
+                targetType.GetPublicStaticMethod(nameof(int.Parse), stringParameter.Type));
+
+            var stringToIntParseLambda = Expression.Lambda<Func<string, int>>(body, stringParameter);
+
+            var translated = ToReadableString(stringToIntParseLambda.Body);
+
+            translated.ShouldBe("int.Parse(str)");
+        }
     }
 }

ReadableExpressions/Translators/CastExpressionTranslator.cs

@@ -36,7 +36,13 @@ public string Translate(Expression expression, TranslationContext context)
 
         private static string TranslateCast(Expression expression, TranslationContext context)
         {
-            var operand = ((UnaryExpression)expression).Operand;
+            var cast = (UnaryExpression)expression;
+            var operand = cast.Operand;
+
+            if ((cast.Method != null) && !cast.Method.IsExplicitOperator() && !cast.Method.IsImplicitOperator())
+            {
+                return TranslateMethodConversion(cast, context);
+            }
 
             if (expression.Type == typeof(object))
             {
@@ -67,6 +73,16 @@ private static string TranslateCast(Expression expression, TranslationContext co
             return TranslateCastCore(expression, context);
         }
 
+        private static string TranslateMethodConversion(UnaryExpression cast, TranslationContext context)
+        {
+            return MethodCallExpressionTranslator.GetMethodCall(
+                cast.Method.DeclaringType.GetFriendlyName(),
+                new BclMethodInfoWrapper(cast.Method),
+                new[] { cast.Operand },
+                cast,
+                context);
+        }
+
         private static string TranslateCastCore(Expression expression, TranslationContext context)
         {
             var cast = (UnaryExpression)expression;