Add support for resolving "operator true".

ICSharpCode.NRefactory.CSharp/Resolver/CSharpResolver.cs

@@ -2095,6 +2095,25 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 		#endregion
 		
 		#region ResolveConditional
+		/// <summary>
+		/// Converts the input to <c>bool</c> using the rules for boolean expressions.
+		/// That is, <c>operator true</c> is used if a regular conversion to <c>bool</c> is not possible.
+		/// </summary>
+		public ResolveResult ResolveCondition(ResolveResult input)
+		{
+			if (input == null)
+				throw new ArgumentNullException("input");
+			IType boolean = compilation.FindType(KnownTypeCode.Boolean);
+			Conversion c = conversions.ImplicitConversion(input, boolean);
+			if (!c.IsValid) {
+				var opTrue = input.Type.GetMethods(m => m.IsOperator && m.Name == "op_True").FirstOrDefault();
+				if (opTrue != null) {
+					c = Conversion.UserDefinedImplicitConversion(opTrue, false);
+				}
+			}
+			return Convert(input, boolean, c);
+		}
+		
 		public ResolveResult ResolveConditional(ResolveResult condition, ResolveResult trueExpression, ResolveResult falseExpression)
 		{
 			// C# 4.0 spec §7.14: Conditional operator
@@ -2131,7 +2150,7 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 			} else {
 				return ErrorResult;
 			}
-			isValid &= TryConvert(ref condition, compilation.FindType(KnownTypeCode.Boolean));
+			condition = ResolveCondition(condition);
 			if (isValid) {
 				if (condition.IsCompileTimeConstant && trueExpression.IsCompileTimeConstant && falseExpression.IsCompileTimeConstant) {
 					bool? val = condition.ConstantValue as bool?;

ICSharpCode.NRefactory.CSharp/Resolver/ResolveVisitor.cs

@@ -2604,7 +2604,11 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 			if (resolverEnabled) {
 				for (AstNode child = conditionStatement.FirstChild; child != null; child = child.NextSibling) {
 					if (child.Role == AstNode.Roles.Condition) {
-						ResolveAndProcessConversion((Expression)child, resolver.Compilation.FindType(KnownTypeCode.Boolean));
+						Expression condition = (Expression)child;
+						ResolveResult conditionRR = Resolve(condition);
+						ResolveResult convertedRR = resolver.ResolveCondition(conditionRR);
+						if (convertedRR != conditionRR)
+							ProcessConversionResult(condition, convertedRR as ConversionResolveResult);
 					} else {
 						Scan(child);
 					}

ICSharpCode.NRefactory.Tests/CSharp/Parser/TypeMembers/OperatorDeclarationTests.cs

@@ -64,5 +64,11 @@ namespace ICSharpCode.NRefactory.CSharp.Parser.TypeMembers
 			Assert.AreEqual("MyObject", ((SimpleType)od.ReturnType).Identifier);
 			Assert.AreEqual("op_UnaryPlus", od.Name);
 		}
+		
+		[Test, Ignore("Parser crash")]
+		public void InvalidOperatorTrueDeclaration()
+		{
+			ParseUtilCSharp.ParseTypeMember<OperatorDeclaration>("public static implicit operator true(MyBool b) {}", expectErrors: true);
+		}
 	}
 }

ICSharpCode.NRefactory.Tests/CSharp/Resolver/ConditionalOperatorTests.cs

@@ -165,5 +165,37 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 			AssertType(typeof(StringComparison), resolver.ResolveConditional(
 				MakeResult(typeof(bool)), MakeResult(typeof(StringComparison)), MakeConstant(0)));
 		}
+		
+		[Test]
+		public void TypeWithImplicitConversionToBool()
+		{
+			string program = @"struct MyBool {
+	public static implicit operator bool(MyBool b) {}
+	void Test() {
+		var x = $this$ ? 1 : 0;
+	}
+}";
+			Assert.AreEqual("System.Boolean", GetExpectedType(program).ReflectionName);
+			Conversion c = GetConversion(program);
+			Assert.IsTrue(c.IsValid);
+			Assert.IsTrue(c.IsUserDefined);
+			Assert.AreEqual("op_Implicit", c.Method.Name);
+		}
+		
+		[Test]
+		public void TypeWithOperatorTrue()
+		{
+			string program = @"struct MyBool {
+	public static bool operator true(MyBool b) {}
+	void Test() {
+		var x = $this$ ? 1 : 0;
+	}
+}";
+			Assert.AreEqual("System.Boolean", GetExpectedType(program).ReflectionName);
+			Conversion c = GetConversion(program);
+			Assert.IsTrue(c.IsValid);
+			Assert.IsTrue(c.IsUserDefined);
+			Assert.AreEqual("op_True", c.Method.Name);
+		}
 	}
 }