Fix those pesky Expression.Parameter() warnings!

java.interop.diff

diff --git a/src/Java.Interop/Java.Interop/JniRuntime.JniMarshalMemberBuilder.cs b/src/Java.Interop/Java.Interop/JniRuntime.JniMarshalMemberBuilder.cs
index 58898be5..cada2bca 100644
--- a/src/Java.Interop/Java.Interop/JniRuntime.JniMarshalMemberBuilder.cs
+++ b/src/Java.Interop/Java.Interop/JniRuntime.JniMarshalMemberBuilder.cs
@@ -9,6 +9,8 @@ using System.Reflection;
 using System.Runtime.CompilerServices;
 using System.Text;
 
+using Java.Interop.Expressions;
+
 namespace Java.Interop {
 
 	partial class JniRuntime {
@@ -175,6 +177,21 @@ namespace Java.Interop {
 					methodParameters [0].ParameterType == typeof (IntPtr) &&
 					methodParameters [1].ParameterType == typeof (IntPtr);
 			}
+
+			internal virtual JniExpressionValueMarshaler GetExpressionValueMarshaler (Type type)
+			{
+				throw new NotSupportedException ();
+			}
+
+			internal virtual Expression DefaultReturnObjectReferenceToJni (JniValueMarshaler marshaler, JniValueMarshalerContext context, string? namePrefix, Expression sourceValue)
+			{
+				throw new NotSupportedException ();
+			}
+
+			internal virtual Expression DefaultDisposeObjectReference (Expression sourceValue)
+			{
+				throw new NotSupportedException ();
+			}
 		}
 	}
 
diff --git a/src/Java.Interop/Java.Interop/JniValueMarshaler.cs b/src/Java.Interop/Java.Interop/JniValueMarshaler.cs
index d3351c35..0989d30c 100644
--- a/src/Java.Interop/Java.Interop/JniValueMarshaler.cs
+++ b/src/Java.Interop/Java.Interop/JniValueMarshaler.cs
@@ -38,6 +38,13 @@ namespace Java.Interop.Expressions {
 			ValueManager   = vm;
 		}
 	}
+
+	internal abstract class JniExpressionValueMarshaler {
+
+		public  abstract    Expression              CreateParameterToManagedExpression (JniValueMarshaler marshaler, JniValueMarshalerContext context, ParameterExpression sourceValue, ParameterAttributes synchronize, Type? targetType);
+		public  abstract    Expression              CreateReturnValueFromManagedExpression (JniValueMarshaler marshaler, JniValueMarshalerContext context, ParameterExpression sourceValue);
+		public  abstract    Expression              CreateParameterFromManagedExpression (JniValueMarshaler marshaler, JniValueMarshalerContext context, ParameterExpression sourceValue, ParameterAttributes synchronize);
+	}
 }
 
 namespace Java.Interop {
@@ -147,72 +154,40 @@ namespace Java.Interop {
 
 		public  virtual     Expression              CreateParameterToManagedExpression (JniValueMarshalerContext context, ParameterExpression sourceValue, ParameterAttributes synchronize = 0, Type? targetType = null)
 		{
-			Func<IntPtr, Type, object?> m   = CreateValue;
-
-			var self    = CreateSelf (context, sourceValue);
-
-			var call    = Expression.Call (self, m.GetMethodInfo (), sourceValue, Expression.Constant (targetType, typeof (Type)));
-			return targetType == null
-				? (Expression) call
-				: Expression.Convert (call, targetType);
-		}
-
-		Expression CreateSelf (JniValueMarshalerContext context, ParameterExpression sourceValue)
-		{
-			var self = Expression.Variable (GetType (), sourceValue.Name + "_marshaler");
-			context.LocalVariables.Add (self);
-			context.CreationStatements.Add (Expression.Assign (self, Expression.New (GetType ())));
-			return self;
+			return JniEnvironment.Runtime.MarshalMemberBuilder?.GetExpressionValueMarshaler (MarshalType)
+				?.CreateParameterToManagedExpression (
+					this, context, sourceValue, synchronize, targetType
+			) ?? throw new NotSupportedException ("No MarshalMemberBuilder support!");
 		}
 
 		public  virtual     Expression              CreateReturnValueFromManagedExpression (JniValueMarshalerContext context, ParameterExpression sourceValue)
 		{
-			CreateParameterFromManagedExpression (context, sourceValue, 0);
-			var s   = context.LocalVariables [sourceValue.Name + "_state"];
-			return ReturnObjectReferenceToJni (context, sourceValue.Name, Expression.Property (s, "ReferenceValue"));
+			return JniEnvironment.Runtime.MarshalMemberBuilder?.GetExpressionValueMarshaler (MarshalType)
+				?.CreateReturnValueFromManagedExpression (
+					this, context, sourceValue
+			) ?? throw new NotSupportedException ("No MarshalMemberBuilder support!");
 		}
 
 		protected Expression ReturnObjectReferenceToJni (JniValueMarshalerContext context, string? namePrefix, Expression sourceValue)
 		{
-			Func<JniObjectReference, IntPtr>    m = JniEnvironment.References.NewReturnToJniRef;
-			var r   = Expression.Variable (MarshalType, namePrefix + "_rtn");
-			if (context == null)
-				throw new ArgumentNullException (nameof (context));
-			context.LocalVariables.Add (r);
-			context.CreationStatements.Add (
-				Expression.Assign (r,
-					Expression.Call (m.GetMethodInfo (), sourceValue)));
-			return r;
+			return JniEnvironment.Runtime.MarshalMemberBuilder?.DefaultReturnObjectReferenceToJni (
+				this, context, namePrefix, sourceValue
+			) ?? throw new NotSupportedException ("No MarshalMemberBuilder support!");
 		}
 
-		delegate void DestroyArgumentStateCb (object value, ref JniValueMarshalerState state, ParameterAttributes synchronize);
 		public  virtual     Expression              CreateParameterFromManagedExpression (JniValueMarshalerContext context, ParameterExpression sourceValue, ParameterAttributes synchronize)
 		{
-			Func<object, ParameterAttributes, JniValueMarshalerState>   c   = CreateArgumentState;
-			DestroyArgumentStateCb                                      d   = DestroyArgumentState;
-
-			var self    = CreateSelf (context, sourceValue);
-			var state   = Expression.Variable (typeof(JniValueMarshalerState), sourceValue.Name + "_state");
-			var ret     = Expression.Variable (MarshalType, sourceValue.Name + "_val");
-
-			context.LocalVariables.Add (state);
-			context.LocalVariables.Add (ret);
-			context.CreationStatements.Add (Expression.Assign (state, Expression.Call (self, c.GetMethodInfo (), Expression.Convert (sourceValue, typeof (object)), Expression.Constant (synchronize, typeof (ParameterAttributes)))));
-			context.CreationStatements.Add (
-					Expression.Assign (ret,
-						Expression.Property (
-							Expression.Property (state, "ReferenceValue"),
-							"Handle")));
-			context.CleanupStatements.Add (Expression.Call (self, d.GetMethodInfo (), Expression.Convert (sourceValue, typeof (object)), state, Expression.Constant (synchronize)));
-
-			return ret;
+			return JniEnvironment.Runtime.MarshalMemberBuilder?.GetExpressionValueMarshaler (MarshalType)
+				?.CreateParameterFromManagedExpression (
+					this, context, sourceValue, synchronize
+			) ?? throw new NotSupportedException ("No MarshalMemberBuilder support!");
 		}
 
-		delegate void DisposeObjRef (ref JniObjectReference r);
 		protected static Expression DisposeObjectReference (Expression sourceValue)
 		{
-			DisposeObjRef   m   = JniObjectReference.Dispose;
-			return Expression.Call (m.GetMethodInfo (), sourceValue);
+			return JniEnvironment.Runtime.MarshalMemberBuilder?.DefaultDisposeObjectReference (
+				sourceValue
+			) ?? throw new NotSupportedException ("No MarshalMemberBuilder support!");
 		}
 	}
 
diff --git a/src/Java.Interop/Properties/AssemblyInfo.cs b/src/Java.Interop/Properties/AssemblyInfo.cs
index e394f102..b5f34206 100644
--- a/src/Java.Interop/Properties/AssemblyInfo.cs
+++ b/src/Java.Interop/Properties/AssemblyInfo.cs
@@ -8,6 +8,13 @@ using System.Runtime.InteropServices;
 [assembly: AssemblyTrademark ("Microsoft Corporation")]
 [assembly: AssemblyMetadata ("IsTrimmable", "True")]
 
+[assembly: InternalsVisibleTo (
+	"Java.Interop.Export, PublicKey=" +
+	"0024000004800000940000000602000000240000525341310004000011000000438ac2a5acfbf1" +
+	"6cbd2b2b47a62762f273df9cb2795ceccdf77d10bf508e69e7a362ea7a45455bbf3ac955e1f2e2" +
+	"814f144e5d817efc4c6502cc012df310783348304e3ae38573c6d658c234025821fda87a0be8a0" +
+	"d504df564e2c93b2b878925f42503e9d54dfef9f9586d9e6f38a305769587b1de01f6c0410328b" +
+	"2c9733db")]
 [assembly: InternalsVisibleTo (
 	"Java.Interop.GenericMarshaler, PublicKey=" +
 	"0024000004800000940000000602000000240000525341310004000011000000438ac2a5acfbf1" +