[C] avoid AmbiguousMatchexception in Bindings

Xamarin.Forms.Core/Xaml/TypeConversionExtensions.cs

@@ -196,17 +196,41 @@ internal static MethodInfo GetImplicitConversionOperator(this Type onType, Type
 		{
 #if NETSTANDARD1_0
 			var mi = onType.GetRuntimeMethod("op_Implicit", new[] { fromType });
-#else
-			var bindingFlags = BindingFlags.Public | BindingFlags.Static | BindingFlags.FlattenHierarchy;
-			var mi = onType.GetMethod("op_Implicit", bindingFlags, null, new[] { fromType }, null);
-#endif
 			if (mi == null) return null;
 			if (!mi.IsSpecialName) return null;
 			if (!mi.IsPublic) return null;
 			if (!mi.IsStatic) return null;
 			if (!toType.IsAssignableFrom(mi.ReturnType)) return null;
 
-			return mi;
+			return mi;		
+#else
+			var bindingAttr = BindingFlags.Public | BindingFlags.Static | BindingFlags.FlattenHierarchy;
+			IEnumerable<MethodInfo> mis = null;
+			try {
+				mis = new[] { onType.GetMethod("op_Implicit", bindingAttr, null, new[] { fromType }, null) };
+			} catch (AmbiguousMatchException) {
+				mis = new List<MethodInfo>();
+				foreach (var mi in onType.GetMethods(bindingAttr)) {
+					if (mi.Name != "op_Implicit") break;
+					var p = mi.GetParameters()?.FirstOrDefault();
+					if (p == null) continue;
+					if (!p.ParameterType.IsAssignableFrom(fromType)) continue;
+					((List<MethodInfo>)mis).Add(mi);
+				}
+			}
+
+			foreach (var mi in mis) {
+				if (mi == null) continue;
+				if (!mi.IsSpecialName) continue;
+				if (!mi.IsPublic) continue;
+				if (!mi.IsStatic) continue;
+				if (!toType.IsAssignableFrom(mi.ReturnType)) continue;
+
+				return mi;
+			}
+			return null;
+#endif
+
 		}
 	}
 }

Xamarin.Forms.Xaml.UnitTests/Issues/Gh4215.xaml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" x:Class="Xamarin.Forms.Xaml.UnitTests.Gh4215">
+	<Label x:Name="l0" Text="{Binding .}" />
+</ContentPage>

Xamarin.Forms.Xaml.UnitTests/Issues/Gh4215.xaml.cs

@@ -0,0 +1,53 @@
+using System;
+using System.Collections.Generic;
+using NUnit.Framework;
+using Xamarin.Forms;
+using Xamarin.Forms.Core.UnitTests;
+
+namespace Xamarin.Forms.Xaml.UnitTests
+{
+	public partial class Gh4215 : ContentPage
+	{
+		public class Gh4215VM
+		{
+			public static implicit operator DateTime(Gh4215VM value) => DateTime.UtcNow;
+			public static implicit operator string(Gh4215VM value) => "foo";
+			public static implicit operator long(Gh4215VM value) => long.MaxValue;
+			public static implicit operator Rectangle(Gh4215VM value) => new Rectangle();
+		}
+
+		public Gh4215()
+		{
+			InitializeComponent();
+		}
+
+		public Gh4215(bool useCompiledXaml)
+		{
+			//this stub will be replaced at compile time
+		}
+
+		[TestFixture]
+		class Tests
+		{
+			[SetUp]
+			public void Setup()
+			{
+				Device.PlatformServices = new MockPlatformServices();
+			}
+
+			[TearDown]
+			public void TearDown()
+			{
+				Device.PlatformServices = null;
+			}
+
+			[TestCase(true), TestCase(false)]
+			public void AvoidAmbiguousMatch(bool useCompiledXaml)
+			{
+				var layout = new Gh4215();
+				Assert.DoesNotThrow(() => layout.BindingContext = new Gh4215VM());
+				Assert.That(layout.l0.Text, Is.EqualTo("foo"));
+			}
+		}
+	}
+}

Xamarin.Forms.Xaml.UnitTests/Xamarin.Forms.Xaml.UnitTests.csproj

@@ -655,6 +655,9 @@
     <Compile Include="Issues\Gh4099.xaml.cs">
       <DependentUpon>Gh4099.xaml</DependentUpon>
     </Compile>
+    <Compile Include="Issues\Gh4215.xaml.cs">
+      <DependentUpon>Gh4215.xaml</DependentUpon>
+    </Compile>
   </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
   <PropertyGroup>
@@ -1207,6 +1210,10 @@
       <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
       <SubType>Designer</SubType>
     </EmbeddedResource>
+    <EmbeddedResource Include="Issues\Gh4215.xaml">
+      <SubType>Designer</SubType>
+      <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
+    </EmbeddedResource>
   </ItemGroup>
   <ItemGroup>
     <Service Include="{82A7F48D-3B50-4B1E-B82E-3ADA8210C358}" />