[class-parse] JavaApiParameterNames use ; for comments (#213)

Change the `JavaDocletType.JavaApiParameterNamesXml` comment
character from `#` to `;`. This is because the parameter description
file format uses `#ctor` for constructors, which obviously interacts
very badly when "`#` until end of line" is a comment.

(Constructors can't be expressed!)
  
This issue was uncovered at API Level 26 which started to contain
generic constructors.

Author: atsushieno

build-tools/xamarin-android-docimporter-ng/Xamarin.Android.ApiTools.ParameterNameExtractor/JavaApiParameterNamesExporter.cs

@@ -80,12 +80,12 @@ public static void WriteParameterNamesXml (this JavaApi api, XmlWriter writer)
  * The Text Format is:
  * 
  * package {packagename}
- * #---------------------------------------
+ * ;---------------------------------------
  *   interface {interfacename}{optional_type_parameters} -or-
  *   class {classname}{optional_type_parameters}
  *     {optional_type_parameters}{methodname}({parameters})
  * 
- * Anything after # is treated as comment.
+ * Anything after ; is treated as comment.
  * 
  * optional_type_parameters: "" -or- "<A,B,C>" (no constraints allowed)
  * parameters: type1 p0, type2 p1 (pairs of {type} {name}, joined by ", ")
@@ -118,7 +118,7 @@ public static void WriteParameterNamesText (this JavaApi api, TextWriter writer)
 			foreach (var package in api.Packages) {
 				writer.WriteLine ();
 				writer.WriteLine ($"package {package.Name}");
-				writer.WriteLine ("#---------------------------------------");
+				writer.WriteLine (";---------------------------------------");
 
 				foreach (var type in package.Types) {
 					if (!type.Members.OfType<JavaMethodBase> ().Any (m => m.Parameters.Any ()))

src/Xamarin.Android.Tools.Bytecode/JavaParameterNamesLoader.cs

@@ -45,12 +45,12 @@ class Package
 		 * The Text Format is:
 		 * 
 		 * package {packagename}
-		 * #---------------------------------------
+		 * ;---------------------------------------
 		 *   interface {interfacename}{optional_type_parameters} -or-
 		 *   class {classname}{optional_type_parameters}
 		 *     {optional_type_parameters}{methodname}({parameters})
 		 * 
-		 * Anything after # is treated as comment.
+		 * Anything after ; is treated as comment.
 		 * 
 		 * optional_type_parameters: "" -or- "<A,B,C>" (no constraints allowed)
 		 * parameters: type1 p0, type2 p1 (pairs of {type} {name}, joined by ", ")
@@ -74,8 +74,10 @@ List<Package> LoadParameterFixupDescription (string path)
 			var types = new List<Type> ();
 			string type = null;
 			var methods = new List<Method> ();
+			int currentLine = 0;
 			foreach (var l in File.ReadAllLines (path)) {
-				var line = l.IndexOf ('#') >= 0 ? l.Substring (0, l.IndexOf ('#')) : l;
+				currentLine++;
+				var line = l.IndexOf (';') >= 0 ? l.Substring (0, l.IndexOf (';')).TrimEnd (' ', '\t') : l;
 				if (line.Trim ().Length == 0)
 					continue;
 				if (line.StartsWith ("package ", StringComparison.Ordinal)) {
@@ -85,6 +87,8 @@ List<Package> LoadParameterFixupDescription (string path)
 					continue;
 				} else if (line.StartsWith ("    ", StringComparison.Ordinal)) {
 					int open = line.IndexOf ('(');
+					if (open < 0)
+						throw new ArgumentException ($"Unexpected line in {path} line {currentLine}: {line}");
 					string parameters = line.Substring (open + 1).TrimEnd (')');
 					string name = line.Substring (4, open - 4);
 					if (name.FirstOrDefault () == '<') // generic method can begin with type parameters.

src/Xamarin.Android.Tools.Bytecode/Tests/ParameterDescription.txt

@@ -1,3 +1,6 @@
-package java.util
+
+; This is a comment line.
+package java.util ; Anything after semicolon is comment.
   class Collection<E>
     add(E e)
+    #ctor()