Mono runtime crashes when running Vagabond

[eiriktsarpalis]

The MethodInfo.GetInstructions() extension found in Mono.Reflection can result in crashes when parsing dynamic assembly IL. This makes Vagrant practically unusable in mono. The following F# script reproduces the issue

#r "Mono.Reflection.dll" // the standard Mono.Reflection library found on nuget

open System
open System.Reflection
open Mono.Reflection

type Foo<'T> = Foo of 'T

type Mapper =
    static member map (f : 'a -> 'b, Foo x) = Foo (f x)


let m = typeof<Mapper>.GetMethod("map")

let instructions = m.GetInstructions()

let field = 
    instructions 
    |> Seq.pick(fun i -> match i.Operand with :? FieldInfo as f -> Some f | _ -> None)


field.ToString() // "a item"

field.MetadataToken // crashes with '* Assertion at reflection.c:7764, condition `field_index >= 0 && field_index < dgclass->count_fields' not met'

[eiriktsarpalis]

A somewhat related issue occurs when attempting to call .GetRawConstantValue() on dynamic assembly fields.

See also https://github.com/mono/mono/blob/master/mono/metadata/icall.c#L1900

[eiriktsarpalis]

Also related is the fact that mono does not support the .GetCustomAttributes() method for generic dynamic types. For instance

Nessos.FsPickler.PicklerGenerationException: Error generating pickler for type 'FSI_0049+runAsync@6[FSI_0049+Bar`1[System.Int32][]]'. ---> System.NotSupportedException: Operation is not supported.
  at System.Reflection.MonoGenericClass.GetCustomAttributes (System.Type attributeType, Boolean inherit) [0x00000] in <filename unknown>:0 
  at Microsoft.FSharp.Reflection.Impl.tryFindCompilationMappingAttributeFromType (System.Type typ) [0x00000] in <filename unknown>:0 
  at Microsoft.FSharp.Reflection.Impl.tryFindSourceConstructFlagsOfType (System.Type typ) [0x00000] in <filename unknown>:0 
  at Microsoft.FSharp.Reflection.Impl.isUnionType (System.Type typ, BindingFlags bindingFlags) [0x00000] in <filename unknown>:0 
  at Microsoft.FSharp.Reflection.Impl.get@470-1 (BindingFlags bindingFlags, System.Type typ) [0x00000] in <filename unknown>:0 
  at Microsoft.FSharp.Reflection.Impl.isConstructorRepr (System.Type typ, BindingFlags bindingFlags) [0x00000] in <filename unknown>:0 
  at Microsoft.FSharp.Reflection.Impl.getTypeOfReprType (System.Type typ, BindingFlags bindingFlags) [0x00000] in <filename unknown>:0 
  at Microsoft.FSharp.Reflection.FSharpType.IsUnion (System.Type typ, Microsoft.FSharp.Core.FSharpOption`1 bindingFlags) [0x00000] in <filename unknown>:0 

See also https://github.com/mono/mono/blob/master/mcs/class/corlib/System.Reflection/MonoGenericClass.cs#L503

[eiriktsarpalis]

Filed a related bug report https://bugzilla.xamarin.com/show_bug.cgi?id=23769

[eiriktsarpalis]

Filed related bug report https://bugzilla.xamarin.com/show_bug.cgi?id=33208

[dsyme]

I'm glad to say this is now the one-and-only open issue with vagabond :)