Fixed C# parser bug that occurs when the first parameter of an extension method is decorated with an attribute.

Closes icsharpcode/SharpDevelop#19.

src/Libraries/NRefactory/Project/Src/Ast/Enums.cs

@@ -115,7 +115,8 @@ namespace ICSharpCode.NRefactory.Ast
 		Out = 2,
 		Ref = 4,
 		Params = 8,
-		Optional = 16
+		Optional = 16,
+		This = 32
 	}
 	
 	public enum VarianceModifier

src/Libraries/NRefactory/Project/Src/Parser/CSharp/cs.ATG

@@ -675,6 +675,7 @@ FixedParameter<out ParameterDeclarationExpression p>
 		"ref"    (. mod = ParameterModifiers.Ref; .)
 		| "out"  (. mod = ParameterModifiers.Out; .)
 		| "params" (. mod = ParameterModifiers.Params; .)
+		| "this"  (. mod = ParameterModifiers.This; .)
 	]
 	Type<out type>
 	Identifier (. p = new ParameterDeclarationExpression(type, t.val, mod); .)
@@ -759,7 +760,6 @@ StructMemberDecl<ModifierList m, List<AttributeSection> attributes>
 	BlockStatement stmt = null;
 	List<TemplateDefinition> templates = new List<TemplateDefinition>();
 	TypeReference explicitInterface = null;
-	bool isExtensionMethod = false;
 .)
 =
 	/*--- constant declaration: */         (. m.Check(Modifiers.Constants); .)
@@ -795,7 +795,6 @@ StructMemberDecl<ModifierList m, List<AttributeSection> attributes>
 	[ TypeParameterList<templates> ]
 	
 	"("
-	[ "this" (. isExtensionMethod = true; /* C# 3.0 */ .) ]
 	[ FormalParameterList<p> ] ")"
 	(.	MethodDeclaration methodDeclaration = new MethodDeclaration {
 			Name = qualident,
@@ -806,7 +805,7 @@ StructMemberDecl<ModifierList m, List<AttributeSection> attributes>
 			StartLocation = m.GetDeclarationLocation(startPos),
 			EndLocation = t.EndLocation,
 			Templates = templates,
-			IsExtensionMethod = isExtensionMethod
+			IsExtensionMethod = p.Count > 0 && p[0].ParamModifier == ParameterModifiers.This
 		};
 		if (explicitInterface != null)
 			SafeAdd(methodDeclaration, methodDeclaration.InterfaceImplementations, new InterfaceImplementation(explicitInterface, qualident));
@@ -1017,7 +1016,6 @@ StructMemberDecl<ModifierList m, List<AttributeSection> attributes>
 				/* .NET 2.0 */
 				[ TypeParameterList<templates> ]
 				"(" 
-				[ "this" (. isExtensionMethod = true; .) ]
 				[ FormalParameterList<p> ] ")"
 				(.
 					MethodDeclaration methodDeclaration = new MethodDeclaration {
@@ -1031,7 +1029,7 @@ StructMemberDecl<ModifierList m, List<AttributeSection> attributes>
 						methodDeclaration.InterfaceImplementations.Add(new InterfaceImplementation(explicitInterface, qualident));
 					methodDeclaration.StartLocation = m.GetDeclarationLocation(startPos);
 					methodDeclaration.EndLocation   = t.EndLocation;
-					methodDeclaration.IsExtensionMethod = isExtensionMethod;
+					methodDeclaration.IsExtensionMethod = p.Count > 0 && p[0].ParamModifier == ParameterModifiers.This;
 					methodDeclaration.Templates = templates;
 					AddChild(methodDeclaration);
 				                                       .)

src/Libraries/NRefactory/Test/Parser/TypeLevel/MethodDeclarationTests.cs

@@ -293,6 +293,19 @@ namespace ICSharpCode.NRefactory.Tests.Ast
 			Assert.AreEqual("System.String", md.Parameters[0].TypeReference.Type);
 		}
 		
+		[Test]
+		public void CSharpExtensionMethodWithAttributeTest()
+		{
+			MethodDeclaration md = ParseUtilCSharp.ParseTypeMember<MethodDeclaration>(
+				"public static int ToInt32([Attr] this string s) { return int.Parse(s); }"
+			);
+			Assert.AreEqual("ToInt32", md.Name);
+			Assert.IsTrue(md.IsExtensionMethod);
+			Assert.AreEqual("s", md.Parameters[0].ParameterName);
+			Assert.AreEqual("System.String", md.Parameters[0].TypeReference.Type);
+			Assert.AreEqual(1, md.Parameters[0].Attributes.Count);
+		}
+		
 		[Test]
 		public void CSharpVoidExtensionMethodTest()
 		{

src/Main/ICSharpCode.SharpDevelop.Dom/Project/Src/Interfaces/ParameterModifiers.cs

@@ -15,6 +15,7 @@ namespace ICSharpCode.SharpDevelop.Dom
 		Out = 2,
 		Ref = 4,
 		Params = 8,
-		Optional = 16
+		Optional = 16,
+		This = 32
 	}
 }