A runtime bug was introduced when loading an assembly that contains a cyclic datastructure. The following code is valid Mun code because Foo is garbage collected type (even though its impossible to create this type at runtime).

pub struct Foo {
    foo: Foo
}

When loading a munlib at runtime that contains this type the runtime hangs. This is due to the code in assembly.rs:

When loading the type Foo, if the type Foo is not yet in the TypeTable loading the above snippet will fail.

We could do something by first creating the Arc<TypeInfo> and then injecting it somehow but it raises another interesting question. By storing the Arc<TypeInfo> in the field, we create a cycle. However, storing the type of a field as a Weak<TypeInfo> is also not an option in a case like this:

pub struct Foo {
    bar: Bar
}

pub struct Bar {
    foo: Foo
}

If in the case above we only hold an Arc<TypeInfo> of Bar, the type info of Foo might be dropped which is not what we want.

I see two approaches in solving this:

• Always retain all the TypeInfos ever allocated. Memory will grow over time, but I doubt it will become a major issue.
• Garbage collect TypeInfos.

The first option is definitely the easiest to implement, I recommend we first take that approach and optimize later. WDYT?