[mono] Incorrect target method resolution in ldvirtftn+delegate creation

[vargaz]

Description

Testcase:

using System;

class Foo
{
	public virtual void foo () {
		Console.WriteLine ("BASE");
	}
}

class Derived : Foo
{
	void foo2 (Action a) {
		a ();
	}

	public override void foo () {
		Console.WriteLine ("DERIVED");
		foo2 (base.foo);
	}

	public static void Main(string[] args) {
		var d = new Derived ();
		d.foo ();
    }
}

Expected results:

DERIVED
BASE

Actual result: recursive calls to Derived:foo () causing a stack overflow and crash.
Environment: dotnet/runtime master on arm64

This is caused by this code path in mini-trampolines.c:

		if (delegate->method_ptr == NULL && tramp_info->method == NULL && delegate->target != NULL && method->flags & METHOD_ATTRIBUTE_VIRTUAL) {
			/* tramp_info->method == NULL happens when someone asks us to JIT some delegate's
			 * Invoke method (see compile_special).  In that case if method is virtual, the target
			 * could be some derived class, so we need to find the correct override.
			 */

This only happens on arm64 because arm64 doesn't have fast virtual delegate invoke trampolines, so we bail out of
handle_delegate_ctor ():

		if (invoke_context_used || !mono_get_delegate_virtual_invoke_impl (mono_method_signature_internal (invoke), target_method_context_used ? NULL : method))
			return NULL;

Reproduction Steps

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Expected behavior

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Actual behavior

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Regression?

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Known Workarounds

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Configuration

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Other information

No response

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