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using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;

using ICSharpCode.NRefactory.Semantics;
using ICSharpCode.NRefactory.TypeSystem;
using ICSharpCode.NRefactory.TypeSystem.Implementation;
using NUnit.Framework;

namespace ICSharpCode.NRefactory.CSharp.Resolver
{
	[TestFixture]
	public class OverloadResolutionTests
	{
		readonly ICompilation compilation = new SimpleCompilation(
			CecilLoaderTests.SystemCore, new[] { CecilLoaderTests.Mscorlib });
		
		ResolveResult[] MakeArgumentList(params Type[] argumentTypes)
		{
			return argumentTypes.Select(t => new ResolveResult(compilation.FindType(t))).ToArray();
		}
		
		IMethod MakeMethod(params object[] parameterTypesOrDefaultValues)
		{
			var context = new SimpleTypeResolveContext(compilation.MainAssembly);
			return (IMethod)MakeUnresolvedMethod(parameterTypesOrDefaultValues).CreateResolved(context);
		}
		
		DefaultUnresolvedMethod MakeUnresolvedMethod(params object[] parameterTypesOrDefaultValues)
		{
			var m = new DefaultUnresolvedMethod();
			m.Name = "Method";
			foreach (var typeOrDefaultValue in parameterTypesOrDefaultValues) {
				Type type = typeOrDefaultValue as Type;
				if (type != null)
					m.Parameters.Add(new DefaultUnresolvedParameter(type.ToTypeReference(), string.Empty));
				else if (Type.GetTypeCode(typeOrDefaultValue.GetType()) > TypeCode.Object)
					m.Parameters.Add(new DefaultUnresolvedParameter(typeOrDefaultValue.GetType().ToTypeReference(), string.Empty) {
					                 	DefaultValue = new SimpleConstantValue(typeOrDefaultValue.GetType().ToTypeReference(), typeOrDefaultValue)
					                 });
				else
					throw new ArgumentException(typeOrDefaultValue.ToString());
			}
			return m;
		}
		
		IMethod MakeParamsMethod(params object[] parameterTypesOrDefaultValues)
		{
			var m = MakeUnresolvedMethod(parameterTypesOrDefaultValues);
			((DefaultUnresolvedParameter)m.Parameters.Last()).IsParams = true;
			var context = new SimpleTypeResolveContext(compilation.MainAssembly);
			return (IMethod)m.CreateResolved(context);
		}
		
		IUnresolvedParameter MakeOptionalParameter(ITypeReference type, string name)
		{
			return new DefaultUnresolvedParameter(type, name) {
				DefaultValue = new SimpleConstantValue(type, null)
			};
		}
		
		[Test]
		public void PreferIntOverUInt()
		{
			OverloadResolution r = new OverloadResolution(compilation, MakeArgumentList(typeof(ushort)));
			var c1 = MakeMethod(typeof(int));
			Assert.AreEqual(OverloadResolutionErrors.None, r.AddCandidate(c1));
			Assert.AreEqual(OverloadResolutionErrors.None, r.AddCandidate(MakeMethod(typeof(uint))));
			Assert.IsFalse(r.IsAmbiguous);
			Assert.AreSame(c1, r.BestCandidate);
		}
		
		[Test]
		public void PreferUIntOverLong_FromIntLiteral()
		{
			ResolveResult[] args = { new ConstantResolveResult(compilation.FindType(KnownTypeCode.Int32), 1) };
			OverloadResolution r = new OverloadResolution(compilation, args);
			var c1 = MakeMethod(typeof(uint));
			Assert.AreEqual(OverloadResolutionErrors.None, r.AddCandidate(c1));
			Assert.AreEqual(OverloadResolutionErrors.None, r.AddCandidate(MakeMethod(typeof(long))));
			Assert.IsFalse(r.IsAmbiguous);
			Assert.AreSame(c1, r.BestCandidate);
		}
		
		[Test]
		public void NullableIntAndNullableUIntIsAmbiguous()
		{
			OverloadResolution r = new OverloadResolution(compilation, MakeArgumentList(typeof(ushort?)));
			Assert.AreEqual(OverloadResolutionErrors.None, r.AddCandidate(MakeMethod(typeof(int?))));
			Assert.AreEqual(OverloadResolutionErrors.None, r.AddCandidate(MakeMethod(typeof(uint?))));
			Assert.AreEqual(OverloadResolutionErrors.AmbiguousMatch, r.BestCandidateErrors);
			
			// then adding a matching overload solves the ambiguity:
			Assert.AreEqual(OverloadResolutionErrors.None, r.AddCandidate(MakeMethod(typeof(ushort?))));
			Assert.AreEqual(OverloadResolutionErrors.None, r.BestCandidateErrors);
			Assert.IsNull(r.BestCandidateAmbiguousWith);
		}
		
		[Test]
		public void ParamsMethodMatchesEmptyArgumentList()
		{
			OverloadResolution r = new OverloadResolution(compilation, MakeArgumentList());
			Assert.AreEqual(OverloadResolutionErrors.None, r.AddCandidate(MakeParamsMethod(typeof(int[]))));
			Assert.IsTrue(r.BestCandidateIsExpandedForm);
		}
		
		[Test]
		public void ParamsMethodMatchesOneArgumentInExpandedForm()
		{
			OverloadResolution r = new OverloadResolution(compilation, MakeArgumentList(typeof(int)));
			Assert.AreEqual(OverloadResolutionErrors.None, r.AddCandidate(MakeParamsMethod(typeof(int[]))));
			Assert.IsTrue(r.BestCandidateIsExpandedForm);
		}
		
		[Test]
		public void ParamsMethodMatchesInUnexpandedForm()
		{
			OverloadResolution r = new OverloadResolution(compilation, MakeArgumentList(typeof(int[])));
			Assert.AreEqual(OverloadResolutionErrors.None, r.AddCandidate(MakeParamsMethod(typeof(int[]))));
			Assert.IsFalse(r.BestCandidateIsExpandedForm);
		}
		
		[Test]
		public void LessArgumentsPassedToParamsIsBetter()
		{
			OverloadResolution r = new OverloadResolution(compilation, MakeArgumentList(typeof(int), typeof(int), typeof(int)));
			Assert.AreEqual(OverloadResolutionErrors.None, r.AddCandidate(MakeParamsMethod(typeof(int[]))));
			Assert.AreEqual(OverloadResolutionErrors.None, r.AddCandidate(MakeParamsMethod(typeof(int), typeof(int[]))));
			Assert.IsFalse(r.IsAmbiguous);
			Assert.AreEqual(2, r.BestCandidate.Parameters.Count);
		}
		
		[Test]
		public void CallInvalidParamsDeclaration()
		{
			OverloadResolution r = new OverloadResolution(compilation, MakeArgumentList(typeof(int[,])));
			Assert.AreEqual(OverloadResolutionErrors.ArgumentTypeMismatch, r.AddCandidate(MakeParamsMethod(typeof(int))));
			Assert.IsFalse(r.BestCandidateIsExpandedForm);
		}
		
		[Test]
		public void PreferMethodWithoutOptionalParameters()
		{
			var m1 = MakeMethod();
			var m2 = MakeMethod(1);
			
			OverloadResolution r = new OverloadResolution(compilation, MakeArgumentList());
			Assert.AreEqual(OverloadResolutionErrors.None, r.AddCandidate(m1));
			Assert.AreEqual(OverloadResolutionErrors.None, r.AddCandidate(m2));
			Assert.IsFalse(r.IsAmbiguous);
			Assert.AreSame(m1, r.BestCandidate);
		}
		
		[Test]
		public void SkeetEvilOverloadResolution()
		{
			// http://msmvps.com/blogs/jon_skeet/archive/2010/11/02/evil-code-overload-resolution-workaround.aspx
			
			// static void Foo<T>(T? ignored = default(T?)) where T : struct
			var m1 = MakeUnresolvedMethod();
			m1.TypeParameters.Add(new DefaultUnresolvedTypeParameter(EntityType.Method, 0, "T") { HasValueTypeConstraint = true });
			m1.Parameters.Add(MakeOptionalParameter(
				NullableType.Create(new TypeParameterReference(EntityType.Method, 0)),
				"ignored"
			));
			
			// class ClassConstraint<T> where T : class {}
			var classConstraint = new DefaultUnresolvedTypeDefinition(string.Empty, "ClassConstraint");
			classConstraint.TypeParameters.Add(new DefaultUnresolvedTypeParameter(EntityType.TypeDefinition, 0, "T") { HasReferenceTypeConstraint = true });
			
			// static void Foo<T>(ClassConstraint<T> ignored = default(ClassConstraint<T>))
			// where T : class
			var m2 = MakeUnresolvedMethod();
			m2.TypeParameters.Add(new DefaultUnresolvedTypeParameter(EntityType.Method, 0, "T") { HasReferenceTypeConstraint = true });
			m2.Parameters.Add(MakeOptionalParameter(
				new ParameterizedTypeReference(classConstraint, new[] { new TypeParameterReference(EntityType.Method, 0) }),
				"ignored"
			));
			
			// static void Foo<T>()
			var m3 = MakeUnresolvedMethod();
			m3.TypeParameters.Add(new DefaultUnresolvedTypeParameter(EntityType.Method, 0, "T"));
			
			ICompilation compilation = TypeSystemHelper.CreateCompilation(classConstraint);
			var context = new SimpleTypeResolveContext(compilation.MainAssembly);
			IMethod resolvedM1 = (IMethod)m1.CreateResolved(context);
			IMethod resolvedM2 = (IMethod)m2.CreateResolved(context);
			IMethod resolvedM3 = (IMethod)m3.CreateResolved(context);
			
			// Call: Foo<int>();
			OverloadResolution o;
			o = new OverloadResolution(compilation, new ResolveResult[0], typeArguments: new[] { compilation.FindType(typeof(int)) });
			Assert.AreEqual(OverloadResolutionErrors.None, o.AddCandidate(resolvedM1));
			Assert.AreEqual(OverloadResolutionErrors.ConstructedTypeDoesNotSatisfyConstraint, o.AddCandidate(resolvedM2));
			Assert.AreSame(resolvedM1, o.BestCandidate);
			
			// Call: Foo<string>();
			o = new OverloadResolution(compilation, new ResolveResult[0], typeArguments: new[] { compilation.FindType(typeof(string)) });
			Assert.AreEqual(OverloadResolutionErrors.ConstructedTypeDoesNotSatisfyConstraint, o.AddCandidate(resolvedM1));
			Assert.AreEqual(OverloadResolutionErrors.None, o.AddCandidate(resolvedM2));
			Assert.AreSame(resolvedM2, o.BestCandidate);
			
			// Call: Foo<int?>();
			o = new OverloadResolution(compilation, new ResolveResult[0], typeArguments: new[] { compilation.FindType(typeof(int?)) });
			Assert.AreEqual(OverloadResolutionErrors.ConstructedTypeDoesNotSatisfyConstraint, o.AddCandidate(resolvedM1));
			Assert.AreEqual(OverloadResolutionErrors.ConstructedTypeDoesNotSatisfyConstraint, o.AddCandidate(resolvedM2));
			Assert.AreEqual(OverloadResolutionErrors.None, o.AddCandidate(resolvedM3));
			Assert.AreSame(resolvedM3, o.BestCandidate);
		}
		
		/// <summary>
		/// A lambda of the form "() => default(returnType)"
		/// </summary>
		class MockLambda : LambdaResolveResult
		{
			IType inferredReturnType;
			List<IParameter> parameters = new List<IParameter>();
			
			public MockLambda(IType returnType)
			{
				this.inferredReturnType = returnType;
			}
			
			public override IList<IParameter> Parameters {
				get { return parameters; }
			}
			
			public override Conversion IsValid(IType[] parameterTypes, IType returnType, CSharpConversions conversions)
			{
				return conversions.ImplicitConversion(inferredReturnType, returnType);
			}
			
			public override bool IsImplicitlyTyped {
				get { return false; }
			}
			
			public override bool IsAnonymousMethod {
				get { return false; }
			}
			
			public override bool HasParameterList {
				get { return true; }
			}
			
			public override bool IsAsync {
				get { return false; }
			}
			
			public override ResolveResult Body {
				get { throw new NotImplementedException(); }
			}
			
			public override IType GetInferredReturnType(IType[] parameterTypes)
			{
				return inferredReturnType;
			}
		}
		
		[Test]
		public void BetterConversionByLambdaReturnValue()
		{
			var m1 = MakeMethod(typeof(Func<long>));
			var m2 = MakeMethod(typeof(Func<int>));
			
			// M(() => default(byte));
			ResolveResult[] args = {
				new MockLambda(compilation.FindType(KnownTypeCode.Byte))
			};
			
			OverloadResolution r = new OverloadResolution(compilation, args);
			Assert.AreEqual(OverloadResolutionErrors.None, r.AddCandidate(m1));
			Assert.AreEqual(OverloadResolutionErrors.None, r.AddCandidate(m2));
			Assert.AreSame(m2, r.BestCandidate);
			Assert.AreEqual(OverloadResolutionErrors.None, r.BestCandidateErrors);
		}
		
		[Test]
		public void BetterConversionByLambdaReturnValue_ExpressionTree()
		{
			var m1 = MakeMethod(typeof(Func<long>));
			var m2 = MakeMethod(typeof(Expression<Func<int>>));
			
			// M(() => default(byte));
			ResolveResult[] args = {
				new MockLambda(compilation.FindType(KnownTypeCode.Byte))
			};
			
			OverloadResolution r = new OverloadResolution(compilation, args);
			Assert.AreEqual(OverloadResolutionErrors.None, r.AddCandidate(m1));
			Assert.AreEqual(OverloadResolutionErrors.None, r.AddCandidate(m2));
			Assert.AreSame(m2, r.BestCandidate);
			Assert.AreEqual(OverloadResolutionErrors.None, r.BestCandidateErrors);
		}
		
		[Test]
		public void Lambda_DelegateAndExpressionTreeOverloadsAreAmbiguous()
		{
			var m1 = MakeMethod(typeof(Func<int>));
			var m2 = MakeMethod(typeof(Expression<Func<int>>));
			
			// M(() => default(int));
			ResolveResult[] args = {
				new MockLambda(compilation.FindType(KnownTypeCode.Int32))
			};
			
			OverloadResolution r = new OverloadResolution(compilation, args);
			Assert.AreEqual(OverloadResolutionErrors.None, r.AddCandidate(m1));
			Assert.AreEqual(OverloadResolutionErrors.None, r.AddCandidate(m2));
			Assert.AreEqual(OverloadResolutionErrors.AmbiguousMatch, r.BestCandidateErrors);
		}
	}
}