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//
// Gendarme.Rules.Design.ImplementIComparableCorrectlyRule
//
// Authors:
// Sebastien Pouliot <sebastien@ximian.com>
//
// Copyright (C) 2008 Novell, Inc (http://www.novell.com)
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
using System;
using System.Text;
using Mono.Cecil;
using Gendarme.Framework;
using Gendarme.Framework.Rocks;
using Gendarme.Framework.Helpers;
namespace Gendarme.Rules.Design {
/// <summary>
/// This rule checks for types that implement <c>System.IComparable</c> and verifies
/// that the type overrides the <c>Equals(object)</c> method and overloads the <c>==</c>,
/// <c>!=</c>, <c><</c> and <c>></c> operators.
/// </summary>
/// <example>
/// Bad example:
/// <code>
/// public struct Comparable : IComparable {
///
/// private int x;
///
/// public int CompareTo (object obj)
/// {
/// return x.CompareTo (((Comparable)obj).x);
/// }
/// }
/// </code>
/// </example>
/// <example>
/// Good example:
/// <code>
/// public struct Comparable : IComparable {
///
/// public int CompareTo (object obj)
/// {
/// return x.CompareTo (((Comparable)obj).x);
/// }
///
/// public override bool Equals (object obj)
/// {
/// return x == ((Comparable) obj).x;
/// }
///
/// static public bool operator == (Comparable left, Comparable right)
/// {
/// return (left.x == right.x);
/// }
///
/// static public bool operator != (Comparable left, Comparable right)
/// {
/// return (left.x != right.x);
/// }
///
/// static public bool operator > (Comparable left, Comparable right)
/// {
/// return (left.x > right.x);
/// }
///
/// static public bool operator < (Comparable left, Comparable right)
/// {
/// return (left.x < right.x);
/// }
/// }
/// </code>
/// </example>
/// <remarks>This rule is available since Gendarme 2.0</remarks>
[Problem ("This type implements IComparable so it should override Equals(object) and overload the ==, !=, < and > operators.")]
[Solution ("Implement the suggested method and/or operators.")]
[FxCopCompatibility ("Microsoft.Design", "CA1036:OverrideMethodsOnComparableTypes")]
public class ImplementIComparableCorrectlyRule : Rule, ITypeRule {
public RuleResult CheckType (TypeDefinition type)
{
// rule does not apply to enums, interfaces and to generated code
if (type.IsEnum || type.IsInterface || type.IsGeneratedCode ())
return RuleResult.DoesNotApply;
// rule only applies if the type implements IComparable or IComparable<T>
// Note: we do not use Implements rock because we do not want a recursive answer
bool icomparable = false;
foreach (TypeReference iface in type.Interfaces) {
if (iface.Namespace != "System")
continue;
// catch both System.IComparable and System.IComparable`1<X>
if (iface.Name.StartsWith ("IComparable", StringComparison.Ordinal)) {
icomparable = true;
break;
}
}
if (!icomparable)
return RuleResult.DoesNotApply;
// type should override Equals(object)
if (!type.HasMethod (MethodSignatures.Equals))
Runner.Report (type, Severity.High, Confidence.High, "Missing Equals(object) override.");
// type should implement overloads for ==, !=, < and > operators
// note: report all missing operators as single defect
bool equality = type.HasMethod (MethodSignatures.op_Equality);
bool inequality = type.HasMethod (MethodSignatures.op_Inequality);
bool less_than = type.HasMethod (MethodSignatures.op_LessThan);
bool greater_than = type.HasMethod (MethodSignatures.op_GreaterThan);
if (!equality || !inequality || !less_than || !greater_than) {
StringBuilder sb = new StringBuilder ("Missing operators:");
if (!equality)
sb.Append (" op_Equality (==)");
if (!inequality)
sb.Append (" op_Inequality (!=)");
if (!less_than)
sb.Append (" op_LessThan (<)");
if (!greater_than)
sb.Append (" op_GreaterThan (>)");
// not all languages support operator overloading so we lower the severity a bit
Runner.Report (type, Severity.Medium, Confidence.High, sb.ToString ());
}
return Runner.CurrentRuleResult;
}
}
}
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