Fixed type inference for shift operators. Closes #239.

ICSharpCode.Decompiler/ILAst/TypeAnalysis.cs

@@ -515,14 +515,20 @@ namespace ICSharpCode.Decompiler.ILAst
 				case ILCode.Rem_Un:
 					return InferArgumentsInBinaryOperator(expr, false, expectedType);
 				case ILCode.Shl:
-				case ILCode.Shr:
 					if (forceInferChildren)
 						InferTypeForExpression(expr.Arguments[1], typeSystem.Int32);
-					return InferTypeForExpression(expr.Arguments[0], typeSystem.Int32);
+					if (expectedType != null && (
+						expectedType.MetadataType == MetadataType.Int32 || expectedType.MetadataType == MetadataType.UInt32 ||
+						expectedType.MetadataType == MetadataType.Int64 || expectedType.MetadataType == MetadataType.UInt64)
+					   )
+						return NumericPromotion(InferTypeForExpression(expr.Arguments[0], expectedType));
+					else
+						return NumericPromotion(InferTypeForExpression(expr.Arguments[0], null));
+				case ILCode.Shr:
 				case ILCode.Shr_Un:
 					if (forceInferChildren)
 						InferTypeForExpression(expr.Arguments[1], typeSystem.Int32);
-					return InferTypeForExpression(expr.Arguments[0], typeSystem.UInt32);
+					return NumericPromotion(InferTypeForExpression(expr.Arguments[0], null));
 				case ILCode.CompoundAssignment:
 					{
 						TypeReference varType = InferTypeForExpression(expr.Arguments[0].Arguments[0], null);
@@ -763,6 +769,27 @@ namespace ICSharpCode.Decompiler.ILAst
 			}
 		}
 		
+		/// <summary>
+		/// Promotes primitive types smaller than int32 to int32.
+		/// </summary>
+		/// <remarks>
+		/// Always promotes to signed int32.
+		/// </remarks>
+		TypeReference NumericPromotion(TypeReference type)
+		{
+			if (type == null)
+				return null;
+			switch (type.MetadataType) {
+				case MetadataType.SByte:
+				case MetadataType.Int16:
+				case MetadataType.Byte:
+				case MetadataType.UInt16:
+					return typeSystem.Int32;
+				default:
+					return type;
+			}
+		}
+		
 		TypeReference HandleConversion(int targetBitSize, bool targetSigned, ILExpression arg, TypeReference expectedType, TypeReference targetType)
 		{
 			if (targetBitSize >= NativeInt && expectedType is PointerType) {

ICSharpCode.Decompiler/Tests/TypeAnalysisTests.cs

@@ -24,4 +24,34 @@ public class TypeAnalysisTests
 	{
 		return (byte)(256 - (int)b);
 	}
+	
+	public int GetHashCode(long num)
+	{
+		return (int)num ^ (int)(num >> 32);
+	}
+	
+	public int ShiftByte(byte num)
+	{
+		return (int)num << 8;
+	}
+	
+	public int RShiftByte(byte num)
+	{
+		return num >> 8;
+	}
+	
+	public int RShiftByteWithSignExtension(byte num)
+	{
+		return (sbyte)num >> 8;
+	}
+	
+	public int RShiftSByte(sbyte num)
+	{
+		return num >> 8;
+	}
+	
+	public int RShiftSByteWithZeroExtension(sbyte num)
+	{
+		return (byte)num >> 8;
+	}
 }