[generator] reduce error-prone enumification XPath. (#164)

Until now, we (well, I) had been patient to deal with methodmap enumification
which *requires* distinction between class and interface by adding
"[Interface]" mark on interfaces. It was just to distinguish "class" and
"interface" elements under "package" element.

But... why do we need that? Performance? The impact should be actually
trivial. It can be just anything, we identify an element by @name.

On the other hand, it is very annoying to exactly specify "class" or
"interface" very carefully, because if I make a mistake then the mapping
results in a warning that then I have to carefully check.

Just reduce such chances for errors by requiring less-error-prone XPath.
It should save everyone.

tools/generator/ApiTransform.cs

@@ -31,30 +31,20 @@ public void WriteTransform (StreamWriter sw)
 		{
 			string preserveAttr = PreserveType ? " preserveType=\"true\"" : null;
 
+			string cls = Class.StartsWith ("[Interface]", StringComparison.Ordinal) ? Class.Substring ("[Interface]".Length) : Class;
+
 			if (string.IsNullOrEmpty (Parameter)) {
 				// This is a field
-				sw.WriteLine ("  <attr path=\"/api/package[@name='{0}']/class[@name='{1}']/field[@name='{2}']\" name=\"enumType\"{4}>{3}</attr>", Package, Class, Member, Enum, preserveAttr);
-
-			} else if (Class.StartsWith ("[Interface]") && Parameter == "return") {
-				// This is the return type on an interface method
-				sw.WriteLine ("  <attr path=\"/api/package[@name='{0}']/interface[@name='{1}']/method[@name='{2}']\" name=\"enumReturn\"{4}>{3}</attr>", Package, Class.Substring ("[Interface]".Length), Member, Enum, preserveAttr);
-
-			} else if (Class.StartsWith ("[Interface]")) {
-				// This is the return type on an interface method
-					sw.WriteLine ("  <attr path=\"/api/package[@name='{0}']/interface[@name='{1}']/method[@name='{2}']/parameter[@name='{3}']\" name=\"enumType\"{5}>{4}</attr>", Package, Class.Substring ("[Interface]".Length), Member, Parameter, Enum, preserveAttr);
-
+				sw.WriteLine ("  <attr path=\"/api/package[@name='{0}']/*[@name='{1}']/field[@name='{2}']\" name=\"enumType\"{4}>{3}</attr>", Package, Class, Member, Enum, preserveAttr);		
 			} else if (Parameter == "return") {
-				// This is the return type on a class method
-					sw.WriteLine ("  <attr path=\"/api/package[@name='{0}']/class[@name='{1}']/method[@name='{2}']\" name=\"enumReturn\"{4}>{3}</attr>", Package, Class, Member, Enum, preserveAttr);
-
+				// This is the return type
+				sw.WriteLine ("  <attr path=\"/api/package[@name='{0}']/*[@name='{1}']/method[@name='{2}']\" name=\"enumReturn\"{4}>{3}</attr>", Package, cls, Member, Enum, preserveAttr);
 			} else if (Member == "ctor" || Member == "constructor") {
-				// This is the return type on a class constructor
-					sw.WriteLine ("  <attr path=\"/api/package[@name='{0}']/class[@name='{1}']/constructor/parameter[@name='{2}']\" name=\"enumType\"{4}>{3}</attr>", Package, Class, Parameter, Enum, preserveAttr);
-
+				// This is the return type
+				sw.WriteLine ("  <attr path=\"/api/package[@name='{0}']/*[@name='{1}']/constructor/parameter[@name='{2}']\" name=\"enumType\"{4}>{3}</attr>", Package, cls, Parameter, Enum, preserveAttr);
 			} else {
-				// This is a parameter on a class method
-				sw.WriteLine ("  <attr path=\"/api/package[@name='{0}']/class[@name='{1}']/method[@name='{2}']/parameter[@name='{3}']\" name=\"enumType\"{5}>{4}</attr>", Package, Class, Member, Parameter, Enum, preserveAttr);
-
+				// This is a parameter
+				sw.WriteLine ("  <attr path=\"/api/package[@name='{0}']/*[@name='{1}']/method[@name='{2}']/parameter[@name='{3}']\" name=\"enumType\"{5}>{4}</attr>", Package, cls, Member, Parameter, Enum, preserveAttr);
 			}
 		}
 	}