Fix TypeBuilder.DefineMethodOverride validation error

[buyaa-n]

On TypeBuilder.DefineMethodOverride(MethodInfo methodInfoBody, MethodInfo methodInfoDeclaration) TypeBuilderImpl validates if the methodInfoBody could override the methodInfoDeclaration

runtime/src/libraries/System.Reflection.Emit/src/System/Reflection/Emit/TypeBuilderImpl.cs

Lines 323 to 325 in 3725bfc

	Type baseType = methodInfoDeclaration.DeclaringType!;
	ValidateBaseType(baseType, methodInfoDeclaration.Name);
	ValidateImplementedMethod(methodInfoBody, methodInfoDeclaration);

ValidateBaseType checks if the TypeBuilderImpl implements the declaring type of the methodInfoDeclaration

runtime/src/libraries/System.Reflection.Emit/src/System/Reflection/Emit/TypeBuilderImpl.cs

Lines 345 to 351 in 3725bfc

	private void ValidateBaseType(Type baseType, string methodName)
	{
	if (baseType.IsInterface)
	{
	if (!IsInterfaceImplemented(baseType))
	{
	throw ArgumentExceptionInvalidMethodOverride(methodName);

In case the base type is constructed generic type that involves TypeBuilder (i.e. instance of TypeBuilderInstantiation) it throws as IsAssignableFrom is not implemented.

Static TypeBuilder.GetMethod(...) only allow getting declared methods, so just comparing the instance with the type should be enough for TypeBuilderInstantiation

Fixes #100537

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[jkotas]

If you would like to keep going on the IsAssignableFrom implementation, you may want to steal some non-ref emit tests cases for it. The assignability (for generics in particular) is a complicated algorithm. I am not sure whether it is worth it to try to implement it just for the validation.

[buyaa-n]

For the record: we end up removing DefineMethodOverride validations that doesn't exist in RuntimeTypeBuilder, as those validations was from runtime type loader, not from Reflection.Emit, thank you @jkotas!