[Xamarin.Android.Tools.Bytecode] Kotlin name shadowing support (#573)

Fixes: #571

Don't mark `public` Kotlin methods as `private` if they "shadow" --
share the same name as -- a private property or field.

If a library uses Kotlin's `NAME_SHADOWING` we incorrectly match the
`private` property/field to the `public` method and mark the methods
as `private`.  Given Kotlin:

	@Suppress("NAME_SHADOWING")
	public class NameShadowing {
	    // Property and method
	    private val count: Int = 3
	    fun count(): Int = count
	    
	    // Field and method
	    private var hitCount = 0
	    fun hitCount(): Int = hitCount
	    
	    // Property and setter
	    private var type = 0
	    fun setType(type: Int) = { println (type); }
	}

Then the public methods `NameShadowing.count()`,
`NameShadowing.hitCount()`, and `NameShadowing.setType()` were not
present within the C# binding.

Support name shadowing by only considering `getFoo()` methods as
potential property getters, instead of allowing `foo`.  (Allowing
`foo` was likely incorrect anyways.)

Additionally, when considering if a method is a potential property
setter, also check that the method's return type is `void`.

[Xamarin.Android.Tools.Bytecode] Kotlin name shadowing support (#573)

src/Xamarin.Android.Tools.Bytecode/Kotlin/KotlinFixups.cs

@@ -232,8 +232,7 @@ static FieldInfo FindJavaFieldProperty (KotlinFile kotlinClass, KotlinProperty p
 
 		static MethodInfo FindJavaPropertyGetter (KotlinFile kotlinClass, KotlinProperty property, ClassFile klass)
 		{
-			var possible_methods = klass.Methods.Where (method => (string.Compare (method.GetMethodNameWithoutSuffix (), $"get{property.Name}", true) == 0 ||
-									       string.Compare (method.GetMethodNameWithoutSuffix (), property.Name, true) == 0) &&
+			var possible_methods = klass.Methods.Where (method => string.Compare (method.GetMethodNameWithoutSuffix (), $"get{property.Name}", true) == 0 &&
 									      method.GetParameters ().Length == 0 &&
 									      TypesMatch (method.ReturnType, property.ReturnType, kotlinClass));
 
@@ -245,6 +244,7 @@ static MethodInfo FindJavaPropertySetter (KotlinFile kotlinClass, KotlinProperty
 			var possible_methods = klass.Methods.Where (method => string.Compare (method.GetMethodNameWithoutSuffix (), $"set{property.Name}", true) == 0 &&
 									      property.ReturnType != null &&
 									      method.GetParameters ().Length == 1 &&
+									      method.ReturnType.BinaryName == "V" &&
 									      TypesMatch (method.GetParameters () [0].Type, property.ReturnType, kotlinClass));
 
 			return possible_methods.FirstOrDefault ();

tests/Xamarin.Android.Tools.Bytecode-Tests/KotlinFixupsTests.cs

@@ -236,5 +236,17 @@ public void UnsignedMethodsXml ()
 			Assert.AreEqual ("ubyte[]", xml.Elements ("method").Single (f => f.Attribute ("name").Value == "foo_ubytearray-GBYM_sE").Attribute ("return").Value);
 			Assert.AreEqual ("ubyte[]", xml.Elements ("method").Single (f => f.Attribute ("name").Value == "foo_ubytearray-GBYM_sE").Element ("parameter").Attribute ("type").Value);
 		}
+
+		[Test]
+		public void HandleKotlinNameShadowing ()
+		{
+			var klass = LoadClassFile ("NameShadowing.class");
+
+			KotlinFixups.Fixup (new [] { klass });
+
+			Assert.True (klass.Methods.Single (m => m.Name == "count").AccessFlags.HasFlag (MethodAccessFlags.Public));
+			Assert.True (klass.Methods.Single (m => m.Name == "hitCount").AccessFlags.HasFlag (MethodAccessFlags.Public));
+			Assert.True (klass.Methods.Single (m => m.Name == "setType").AccessFlags.HasFlag (MethodAccessFlags.Public));
+		}
 	}
 }

tests/Xamarin.Android.Tools.Bytecode-Tests/kotlin/NameShadowing.kt

@@ -0,0 +1,14 @@
+@Suppress("NAME_SHADOWING")
+public class NameShadowing {
+	// Property and method
+	private val count: Int = 3
+	fun count(): Int = count
+
+	// Field and method
+	private var hitCount = 0
+	fun hitCount(): Int = hitCount
+
+	// Property and setter
+	private var type = 0
+	fun setType(type: Int) = { println (type); }
+}