Resolution of nested type names is inconsistent between MonoVM and CoreCLR

[filipnavara]

Consider the following code:

using System;

Console.WriteLine(typeof(object).Assembly.GetType("Mono.RuntimeStructs") != null);
Console.WriteLine(Type.GetType($"Foo/Bar, {typeof(Foo).Assembly.FullName}"));
Console.WriteLine(Type.GetType($"Foo+Bar, {typeof(Foo).Assembly.FullName}"));

class Foo
{
    class Bar
    {

    }
}

On MonoVM it prints:

true
Foo+Bar
Foo+Bar

On CoreCLR it prints:

false

Foo+Bar

I thought the type name parser was unified as of .NET 9 but apparently there's still an inconsistency.

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[teo-tsirpanis]

Likely related to Mono test failures in #111598. e1f044c might fix it.

[jkotas]

I thought the type name parser was unified as of .NET 9 but apparently there's still an inconsistency.

Mono type name parsers are not completely unified:

runtime/src/mono/mono/metadata/reflection.c

Line 1682 in 37b1764

_mono_reflection_parse_type (char *name, char **endptr, gboolean is_recursed,

runtime/src/mono/System.Private.CoreLib/src/System/TypeSpec.cs

Line 337 in 37b1764

private static TypeSpec Parse(string name, ref int p, bool is_recurse, bool allow_aqn)

Related/duplicate #45033