Added implicit conversion logic.

ICSharpCode.NRefactory.Tests/TypeSystem/CecilLoaderTests.cs

@@ -60,7 +60,7 @@ namespace ICSharpCode.NRefactory.TypeSystem
 			IMethod toPointer = c.Methods.Single(p => p.Name == "ToPointer");
 			Assert.AreEqual("System.Void*", toPointer.ReturnType.Resolve(ctx).DotNetName);
 			Assert.IsInstanceOf(typeof(PointerType), toPointer.ReturnType.Resolve(ctx));
-			Assert.AreEqual("System.Void", toPointer.ReturnType.Resolve(ctx).GetElementType().FullName);
+			Assert.AreEqual("System.Void", ((PointerType)toPointer.ReturnType.Resolve(ctx)).ElementType.FullName);
 		}
 		
 		[Test]

ICSharpCode.NRefactory/CSharp/Resolver/Conversions.cs

@@ -0,0 +1,264 @@
+// Copyright (c) 2010 AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under MIT X11 license (for details please see \doc\license.txt)
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using ICSharpCode.NRefactory.TypeSystem;
+
+namespace ICSharpCode.NRefactory.CSharp.Resolver
+{
+	public class Conversions
+	{
+		readonly ITypeResolveContext context;
+		readonly IType objectType;
+		
+		public Conversions(ITypeResolveContext context)
+		{
+			if (context == null)
+				throw new ArgumentNullException("context");
+			this.context = context;
+			this.objectType = context.GetClass(typeof(object)) ?? SharedTypes.UnknownType;
+		}
+		
+		#region ImplicitConversion
+		public bool ImplicitConversion(IType fromType, IType toType)
+		{
+			// C# 4.0 spec: §6.1
+			return IdentityConversion(fromType, toType)
+				|| ImplicitNumericConversion(fromType, toType)
+				|| ImplicitEnumerationConversion(fromType, toType)
+				|| ImplicitNullableConversion(fromType, toType)
+				|| NullLiteralConversion(fromType, toType)
+				|| ImplicitReferenceConversion(fromType, toType)
+				|| BoxingConversion(fromType, toType)
+				|| ImplicitConstantExpressionConversion(fromType, toType);
+		}
+		#endregion
+		
+		#region IdentityConversion
+		/// <summary>
+		/// Gets whether there is an identity conversion from <paramref name="fromType"/> to <paramref name="toType"/>
+		/// </summary>
+		bool IdentityConversion(IType fromType, IType toType)
+		{
+			// C# 4.0 spec: §6.1.1
+			DynamicErasure erasure = new DynamicErasure(this);
+			return fromType.AcceptVisitor(erasure).Equals(toType.AcceptVisitor(erasure));
+		}
+		
+		sealed class DynamicErasure : TypeVisitor
+		{
+			readonly IType objectType;
+			
+			public DynamicErasure(Conversions conversions)
+			{
+				this.objectType = conversions.objectType;
+			}
+			
+			public override IType VisitOtherType(IType type)
+			{
+				if (type == SharedTypes.Dynamic)
+					return objectType;
+				else
+					return base.VisitOtherType(type);
+			}
+		}
+		#endregion
+		
+		#region ImplicitNumericConversion
+		static readonly bool[,] implicitNumericConversionLookup = {
+			//       to:   short  ushort  int   uint   long   ulong
+			// from:
+			/* char   */ { false, true , true , true , true , true  },
+			/* sbyte  */ { true , false, true , false, true , false },
+			/* byte   */ { true , true , true , true , true , true  },
+			/* short  */ { false, false, true , false, true , false },
+			/* ushort */ { false, false, true , true , true , true  },
+			/* int    */ { false, false, false, false, true , false },
+			/* uint   */ { false, false, false, false, true , true  },
+		};
+		
+		bool ImplicitNumericConversion(IType fromType, IType toType)
+		{
+			// C# 4.0 spec: §6.1.2
+			
+			TypeCode from = ReflectionHelper.GetTypeCode(fromType);
+			TypeCode to = ReflectionHelper.GetTypeCode(toType);
+			if (to >= TypeCode.Single && to <= TypeCode.Decimal) {
+				// Conversions to float/double/decimal exist from all integral types,
+				// and there's a conversion from float to double.
+				return from >= TypeCode.Char && from <= TypeCode.UInt64
+					|| from == TypeCode.Single && to == TypeCode.Double;
+			} else {
+				// Conversions to integral types: look at the table
+				return from >= TypeCode.Char && from <= TypeCode.UInt32
+					&& to >= TypeCode.Int16 && to <= TypeCode.UInt64
+					&& implicitNumericConversionLookup[to - TypeCode.Int16, from - TypeCode.Char];
+			}
+		}
+		#endregion
+		
+		#region ImplicitEnumerationConversion
+		bool ImplicitEnumerationConversion(IType fromType, IType toType)
+		{
+			// C# 4.0 spec: §6.1.3
+			// TODO: implement ImplicitEnumerationConversion and ImplicitConstantExpressionConversion
+			return false;
+		}
+		#endregion
+		
+		#region ImplicitNullableConversion
+		bool ImplicitNullableConversion(IType fromType, IType toType)
+		{
+			// C# 4.0 spec: §6.1.4
+			IType t = UnpackNullable(toType);
+			if (t != null) {
+				IType s = UnpackNullable(fromType) ?? fromType;
+				return IdentityConversion(s, t) || ImplicitNumericConversion(s, t);
+			} else {
+				return false;
+			}
+		}
+		
+		static IType UnpackNullable(IType type)
+		{
+			ParameterizedType pt = type as ParameterizedType;
+			if (pt != null && pt.TypeArguments.Count == 1 && pt.FullName == "System.Nullable")
+				return pt.TypeArguments[0];
+			else
+				return null;
+		}
+		#endregion
+		
+		#region NullLiteralConversion
+		bool NullLiteralConversion(IType fromType, IType toType)
+		{
+			// C# 4.0 spec: §6.1.5
+			return fromType == SharedTypes.Null && (UnpackNullable(toType) != null);
+			// This function only handles the conversion from the null literal to nullable value types,
+			// reference types are handled by ImplicitReferenceConversion instead.
+		}
+		#endregion
+		
+		#region ImplicitReferenceConversion
+		bool ImplicitReferenceConversion(IType fromType, IType toType)
+		{
+			// C# 4.0 spec: §6.1.6
+			
+			// reference conversions are possible only if both types are known to be reference types
+			if (fromType.IsReferenceType != true || toType.IsReferenceType != true)
+				return false;
+			
+			// conversion from null literal is always possible
+			if (fromType == SharedTypes.Null)
+				return true;
+			
+			ArrayType fromArray = fromType as ArrayType;
+			if (fromArray != null) {
+				ArrayType toArray = toType as ArrayType;
+				if (toArray != null) {
+					// array covariance (the broken kind)
+					return fromArray.Dimensions == toArray.Dimensions
+						&& ImplicitReferenceConversion(fromArray.ElementType, toArray.ElementType);
+				}
+				// conversion from single-dimensional array S[] to IList<T>:
+				ParameterizedType toPT = toType as ParameterizedType;
+				if (fromArray.Dimensions == 1 && toPT != null && toPT.TypeArguments.Count == 1
+				    && toPT.Namespace == "System.Collections.Generic"
+				    && (toPT.Name == "List" || toPT.Name == "Collection" || toPT.Name == "IEnumerable"))
+				{
+					// array covariance plays a part here as well (string[] is IList<object>)
+					return IdentityConversion(fromArray.ElementType, toPT.TypeArguments[0])
+						|| ImplicitReferenceConversion(fromArray.ElementType, toPT.TypeArguments[0]);
+				}
+				// conversion from any array to System.Array and the interfaces it implements:
+				ITypeDefinition systemArray = context.GetClass("System.Array", 0, StringComparer.Ordinal);
+				return systemArray != null && (systemArray.Equals(toType) || ImplicitReferenceConversion(systemArray, toType));
+			}
+			
+			// now comes the hard part: traverse the inheritance chain and figure out generics+variance
+			return IsSubtypeOf(fromType, toType);
+		}
+		
+		// Determines whether s is a subtype of t.
+		// Helper method used for ImplicitReferenceConversion and BoxingConversion
+		bool IsSubtypeOf(IType s, IType t)
+		{
+			// conversion to dynamic + object are always possible
+			if (t == SharedTypes.Dynamic || t.Equals(objectType))
+				return true;
+			
+			foreach (IType baseType in s.GetAllBaseTypes(context)) {
+				if (IdentityOrVarianceConversion(baseType, t))
+					return true;
+			}
+			return false;
+		}
+		
+		bool IdentityOrVarianceConversion(IType s, IType t)
+		{
+			ITypeDefinition def = s.GetDefinition();
+			if (def != null && def.Equals(t.GetDefinition())) {
+				ParameterizedType ps = s as ParameterizedType;
+				ParameterizedType pt = t as ParameterizedType;
+				if (ps != null && pt != null 
+				    && ps.TypeArguments.Count == pt.TypeArguments.Count
+				    && ps.TypeArguments.Count == def.TypeParameters.Count) 
+				{
+					// §13.1.3.2 Variance Conversion
+					for (int i = 0; i < def.TypeParameters.Count; i++) {
+						IType si = ps.TypeArguments[i];
+						IType ti = pt.TypeArguments[i];
+						if (IdentityConversion(si, ti))
+							continue;
+						ITypeParameter xi = def.TypeParameters[i];
+						switch (xi.Variance) {
+							case VarianceModifier.Covariant:
+								if (!ImplicitReferenceConversion(si, ti))
+									return false;
+								break;
+							case VarianceModifier.Contravariant:
+								if (!ImplicitReferenceConversion(ti, si))
+									return false;
+								break;
+						}
+					}
+				} else if (ps != null || pt != null) {
+					return false; // only of of them is parameterized, or counts don't match? -> not valid conversion
+				}
+				return true;
+			}
+			return false;
+		}
+		#endregion
+		
+		#region BoxingConversion
+		bool BoxingConversion(IType fromType, IType toType)
+		{
+			// C# 4.0 spec: §6.1.7
+			fromType = UnpackNullable(fromType) ?? fromType;
+			return fromType.IsReferenceType == false && toType.IsReferenceType == true && IsSubtypeOf(fromType, toType);
+		}
+		#endregion
+		
+		#region ImplicitDynamicConversion
+		bool ImplicitDynamicConversion(IType fromType, IType toType)
+		{
+			// C# 4.0 spec: §6.1.8
+			return fromType == SharedTypes.Dynamic;
+		}
+		#endregion
+		
+		#region ImplicitConstantExpressionConversion
+		bool ImplicitConstantExpressionConversion(IType fromType, IType toType)
+		{
+			// C# 4.0 spec: §6.1.9
+			// TODO: implement ImplicitEnumerationConversion and ImplicitConstantExpressionConversion
+			return false;
+		}
+		#endregion
+		
+		// TODO: add support for user-defined conversions
+	}
+}

ICSharpCode.NRefactory/ICSharpCode.NRefactory.csproj

@@ -139,6 +139,7 @@
     <Compile Include="CSharp\Parser\mcs\MonoSymbolWriter.cs" />
     <Compile Include="CSharp\Parser\mcs\outline.cs" />
     <Compile Include="CSharp\Parser\mcs\roottypes.cs" />
+    <Compile Include="CSharp\Resolver\Conversions.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="TypeSystem\Accessibility.cs" />
     <Compile Include="TypeSystem\AmbiguousType.cs" />
@@ -255,6 +256,7 @@
     <Compile Include="Util\TreeTraversal.cs" />
   </ItemGroup>
   <ItemGroup>
+    <Folder Include="CSharp\Resolver" />
     <Folder Include="Util" />
   </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.Targets" />

ICSharpCode.NRefactory/TypeSystem/ArrayType.cs

@@ -40,7 +40,7 @@ namespace ICSharpCode.NRefactory.TypeSystem
 		
 		public override int GetHashCode()
 		{
-			return unchecked(GetElementType().GetHashCode() * 71681 + dimensions);
+			return unchecked(elementType.GetHashCode() * 71681 + dimensions);
 		}
 		
 		public override bool Equals(IType other)
@@ -55,9 +55,11 @@ namespace ICSharpCode.NRefactory.TypeSystem
 			IType t = context.GetClass(typeof(Array));
 			if (t != null)
 				baseTypes.Add(t);
-			t = context.GetClass(typeof(List<>));
-			if (t != null)
-				baseTypes.Add(t);
+			if (dimensions == 1) { // single-dimensional arrays implement IList<T>
+				t = context.GetClass(typeof(IList<>));
+				if (t != null)
+					baseTypes.Add(t);
+			}
 			return baseTypes;
 		}
 		
@@ -68,7 +70,6 @@ namespace ICSharpCode.NRefactory.TypeSystem
 		
 		public override IType VisitChildren(TypeVisitor visitor)
 		{
-			IType elementType = GetElementType();
 			IType e = elementType.AcceptVisitor(visitor);
 			if (e == elementType)
 				return this;

ICSharpCode.NRefactory/TypeSystem/ByReferenceType.cs

@@ -38,7 +38,6 @@ namespace ICSharpCode.NRefactory.TypeSystem
 		
 		public override IType VisitChildren(TypeVisitor visitor)
 		{
-			IType elementType = GetElementType();
 			IType e = elementType.AcceptVisitor(visitor);
 			if (e == elementType)
 				return this;

ICSharpCode.NRefactory/TypeSystem/ExtensionMethods.cs

@@ -17,7 +17,8 @@ namespace ICSharpCode.NRefactory.TypeSystem
 		/// Gets all base types.
 		/// </summary>
 		/// <remarks>This is the reflexive and transitive closure of <see cref="IType.GetBaseTypes"/>.
-		/// Note that this method does not return all supertypes - doing so is impossible due to contravariance.
+		/// Note that this method does not return all supertypes - doing so is impossible due to contravariance
+		/// (and underisable for covariance and the list could become very large).
 		/// This method may return an infinite list for certain (invalid) class declarations like <c>class C{T} : C{C{T}}</c>
 		/// TODO: we could ensure a finite list by filtering out cyclic inheritance
 		/// </remarks>

ICSharpCode.NRefactory/TypeSystem/IType.cs

@@ -20,17 +20,9 @@ namespace ICSharpCode.NRefactory.TypeSystem
 		/// </returns>
 		bool? IsReferenceType { get; }
 		
-		/// <summary>
-		/// Gets the element type of array or pointer types.
-		/// </summary>
-		/// <exception cref="InvalidOperationException">
-		/// This type is not an array or pointer type.
-		/// </exception>
-		IType GetElementType();
-		
 		/// <summary>
 		/// Gets the underlying type definition.
-		/// Can return null for types which do not have a type definition (for example type parameters)
+		/// Can return null for types which do not have a type definition (for example arrays, pointers, type parameters)
 		/// </summary>
 		ITypeDefinition GetDefinition();
 		
@@ -193,12 +185,6 @@ namespace ICSharpCode.NRefactory.TypeSystem
 			}
 		}
 		
-		IType IType.GetElementType()
-		{
-			Contract.Ensures(Contract.Result<IType>() != null);
-			return null;
-		}
-		
 		ITypeDefinition IType.GetDefinition()
 		{
 			return null;

ICSharpCode.NRefactory/TypeSystem/Implementation/AbstractType.cs

@@ -46,11 +46,6 @@ namespace ICSharpCode.NRefactory.TypeSystem.Implementation
 			get { return null; }
 		}
 		
-		public virtual IType GetElementType()
-		{
-			throw new InvalidOperationException();
-		}
-		
 		public virtual ITypeDefinition GetDefinition()
 		{
 			return null;

ICSharpCode.NRefactory/TypeSystem/Implementation/TypeWithElementType.cs

@@ -34,9 +34,8 @@ namespace ICSharpCode.NRefactory.TypeSystem.Implementation
 		
 		public abstract string NameSuffix { get; }
 		
-		public override IType GetElementType()
-		{
-			return elementType;
+		public IType ElementType {
+			get { return elementType; }
 		}
 		
 		// Force concrete implementations to override VisitChildren - the base implementation

ICSharpCode.NRefactory/TypeSystem/PointerType.cs

@@ -40,7 +40,6 @@ namespace ICSharpCode.NRefactory.TypeSystem
 		
 		public override IType VisitChildren(TypeVisitor visitor)
 		{
-			IType elementType = GetElementType();
 			IType e = elementType.AcceptVisitor(visitor);
 			if (e == elementType)
 				return this;

ICSharpCode.NRefactory/TypeSystem/ReflectionHelper.cs

@@ -2,6 +2,7 @@
 // This code is distributed under MIT X11 license (for details please see \doc\license.txt)
 
 using System;
+using System.Collections.Generic;
 using ICSharpCode.NRefactory.TypeSystem.Implementation;
 
 namespace ICSharpCode.NRefactory.TypeSystem
@@ -131,5 +132,38 @@ namespace ICSharpCode.NRefactory.TypeSystem
 					return reflectionName;
 			}
 		}
+		
+		static readonly Dictionary<string, TypeCode> typeNameToCodeDict = new Dictionary<string, TypeCode> {
+			{ typeof(Boolean).FullName, TypeCode.Boolean },
+			{ typeof(Byte).FullName, TypeCode.Byte },
+			{ typeof(Char).FullName, TypeCode.Char },
+			{ typeof(DateTime).FullName, TypeCode.DateTime },
+			{ typeof(DBNull).FullName, TypeCode.DBNull },
+			{ typeof(Decimal).FullName, TypeCode.Decimal },
+			{ typeof(Double).FullName, TypeCode.Double },
+			{ typeof(Int16).FullName, TypeCode.Int16 },
+			{ typeof(Int32).FullName, TypeCode.Int32 },
+			{ typeof(Int64).FullName, TypeCode.Int64 },
+			{ typeof(Object).FullName, TypeCode.Object },
+			{ typeof(SByte).FullName, TypeCode.SByte },
+			{ typeof(Single).FullName, TypeCode.Single },
+			{ typeof(String).FullName, TypeCode.String },
+			{ typeof(UInt16).FullName, TypeCode.UInt16 },
+			{ typeof(UInt32).FullName, TypeCode.UInt32 },
+			{ typeof(UInt64).FullName, TypeCode.UInt64 }
+		};
+		
+		/// <summary>
+		/// Gets the type code for the specified type, or TypeCode.Empty if none of the other type codes matches.
+		/// </summary>
+		public static TypeCode GetTypeCode(IType type)
+		{
+			ITypeDefinition def = type as ITypeDefinition;
+			TypeCode typeCode;
+			if (def != null && def.TypeParameterCount == 0 && typeNameToCodeDict.TryGetValue(def.FullName, out typeCode))
+				return typeCode;
+			else
+				return TypeCode.Empty;
+		}
 	}
 }