[generator] Ensure property setter parameter name is "value" (#566)

Fixes: #565

In a case with generics, we were not renaming the property setter
parameter to `value`, which meant it could be left as `p0`, which is
not valid C#:

	// This method is explicitly implemented as a member of an instantiated Google.Android.Material.DatePicker.IDateSelector
	global::Java.Lang.Object global::Google.Android.Material.DatePicker.IDateSelector.Selection {
	    // Metadata.xml XPath method reference: path="/api/package[@name='com.google.android.material.datepicker']/interface[@name='DateSelector']/method[@name='getSelection' and count(parameter)=0]"
	    [Register ("getSelection", "()Ljava/lang/Object;", "GetGetSelectionHandler:Google.Android.Material.DatePicker.IDateSelectorInvoker, Xamarin.Google.Android.Material")]
	    get {
	        return Selection;
	    }
	    // Metadata.xml XPath method reference: path="/api/package[@name='com.google.android.material.datepicker']/interface[@name='DateSelector']/method[@name='setSelection' and count(parameter)=1 and parameter[1][@type='S']]"
	    [Register ("setSelection", "(Ljava/lang/Object;)V", "GetSetSelection_Ljava_lang_Object_Handler:Google.Android.Material.DatePicker.IDateSelectorInvoker, Xamarin.Google.Android.Material")]
	    set {
	        Selection = global::Java.Interop.JavaObjectExtensions.JavaCast<global::Java.Lang.Long>(p0);
	    }
	}

This would result in a C# error:

	error CS0103: The name 'p0' does not exist in the current context.

The fix is to temporarily override the property's setter's parameter
name to `value` so that we emit compilable C# code:

	set {
	    Selection = JavaObjectExtensions.JavaCast<Long>(value);
	}

Author: jpobst

tests/generator-Tests/Unit-Tests/CodeGeneratorTests.cs

@@ -967,5 +967,54 @@ public void WriteMethodWithInvalidParameterName ()
 			// Ensure we escape dollar signs
 			Assert.False (result.Contains ("$this"));
 		}
+
+		[Test]
+		public void WritePropertyExplicitInterfaceParameterName ()
+		{
+			// Fix a case where we were not overriding a property setter's parameter name ("p0")
+			// to "value", resulting in invalid C#.  Like:
+			// public string MyProperty {
+			//   set => my_property = p0;
+			// }
+			var gens = ParseApiDefinition (@"<api>
+			  <package name='java.lang' jni-name='java/lang'>
+			    <class abstract='false' deprecated='not deprecated' final='false' name='Object' static='false' visibility='public' jni-signature='Ljava/lang/Object;' />
+			    <class abstract='false' deprecated='not deprecated' extends='java.lang.Object' final='false' name='Long' static='false' visibility='public' jni-signature='Ljava/lang/Long;' />
+			  </package>
+
+			  <package name='com.google.android.material.datepicker' jni-name='com/google/android/material/datepicker'>
+			    <class abstract='false' deprecated='not deprecated' extends='java.lang.Object' extends-generic-aware='java.lang.Object' jni-extends='Ljava/lang/Object;' final='false' name='SingleDateSelector' static='false' visibility='public' jni-signature='Lcom/google/android/material/datepicker/SingleDateSelector;'>
+			      <implements name='com.google.android.material.datepicker.DateSelector' name-generic-aware='com.google.android.material.datepicker.DateSelector&lt;java.lang.Long&gt;' jni-type='Lcom/google/android/material/datepicker/DateSelector&lt;Ljava/lang/Long;&gt;;'>
+			      </implements>
+			      <method abstract='false' deprecated='not deprecated' final='false' name='getSelection' jni-signature='()Ljava/lang/Long;' bridge='false' native='false' return='java.lang.Long' jni-return='Ljava/lang/Long;' static='false' synchronized='false' synthetic='false' visibility='public'>
+			      </method>
+			      <method abstract='false' deprecated='not deprecated' final='false' name='setSelection' jni-signature='(Ljava/lang/Long;)V' bridge='false' native='false' return='void' jni-return='V' static='false' synchronized='false' synthetic='false' visibility='public'>
+				<parameter name='selection' type='java.lang.Long' jni-type='Ljava/lang/Long;'>
+				</parameter>
+			      </method>
+			    </class>
+			    <interface abstract='true' deprecated='not deprecated' final='false' name='DateSelector' static='false' visibility='public' jni-signature='Lcom/google/android/material/datepicker/DateSelector;'>
+			      <typeParameters>
+				<typeParameter name='S' classBound='java.lang.Object' jni-classBound='Ljava/lang/Object;'></typeParameter>
+			      </typeParameters>
+			      <method abstract='true' deprecated='not deprecated' final='false' name='getSelection' jni-signature='()Ljava/lang/Object;' bridge='false' native='false' return='S' jni-return='TS;' static='false' synchronized='false' synthetic='false' visibility='public'>
+			      </method>
+			      <method abstract='true' deprecated='not deprecated' final='false' name='setSelection' jni-signature='(Ljava/lang/Object;)V' bridge='false' native='false' return='void' jni-return='V' static='false' synchronized='false' synthetic='false' visibility='public'>
+				<parameter name='p0' type='S' jni-type='TS;'>
+				</parameter>
+			      </method>
+			    </interface>
+			  </package>
+			</api>");
+
+			var @class = gens.OfType<ClassGen> ().First (c => c.Name == "SingleDateSelector");
+
+			generator.Context.ContextTypes.Push (@class);
+			generator.WriteClass (@class, string.Empty, new GenerationInfo ("", "", "MyAssembly"));
+			generator.Context.ContextTypes.Pop ();
+
+			var result = writer.ToString ().NormalizeLineEndings ();
+			Assert.False (result.Contains ("p0"));
+		}
 	}
 }

tools/generator/Java.Interop.Tools.Generator.CodeGeneration/CodeGenerator.cs

@@ -1605,7 +1605,13 @@ public void WritePropertyExplicitInterface (Property property, string indent, Ge
 				if (property.Setter.GenericArguments != null && property.Setter.GenericArguments.Any ())
 					writer.WriteLine ("{0}{1}", indent, property.Setter.GenericArguments.ToGeneratedAttributeString ());
 				writer.WriteLine ("{0}\t[Register (\"{1}\", \"{2}\", \"{3}:{4}\"{5})] set {{", indent, property.Setter.JavaName, property.Setter.JniSignature, property.Setter.ConnectorName, property.Setter.GetAdapterName (opt, adapter), property.Setter.AdditionalAttributeString ());
+
+				// Temporarily rename the parameter to "value"
+				var pname = property.Setter.Parameters [0].Name;
+				property.Setter.Parameters [0].Name = "value";
 				writer.WriteLine ("{0}\t\t{1} = {2};", indent, property.Name, property.Setter.Parameters.GetGenericCall (opt, mappings));
+				property.Setter.Parameters [0].Name = pname;
+
 				writer.WriteLine ("{0}\t}}", indent);
 			}
 			writer.WriteLine ("{0}}}", indent);