1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87

#[cfg(feature = "gc")]
mod enabled;
#[cfg(feature = "gc")]
pub use enabled::*;

#[cfg(not(feature = "gc"))]
mod disabled;
#[cfg(not(feature = "gc"))]
pub use disabled::*;

use std::ops::Deref;

/// A common trait implemented by all garbage-collected reference types.
///
/// This is a sealed trait, and may not be implemented for any types outside of
/// the `wasmtime` crate.
pub trait GcRef: GcRefImpl {}

impl<T> GcRef for T where T: GcRefImpl {}

/// A trait implemented for GC references that are guaranteed to be rooted:
///
/// * [`Rooted<T>`][crate::Rooted]
/// * [`ManuallyRooted<T>`][crate::ManuallyRooted]
///
/// You can use this to abstract over the different kinds of rooted GC
/// references. Note that `Deref<Target = T>` is a supertrait for
/// `RootedGcRef<T>`, so all rooted GC references deref to their underlying `T`,
/// allowing you to call its methods.
///
/// This is a sealed trait, and may not be implemented for any types outside of
/// the `wasmtime` crate.
pub trait RootedGcRef<T>: RootedGcRefImpl<T> + Deref<Target = T>
where
    T: GcRef,
{
}

impl<T, U> RootedGcRef<T> for U
where
    T: GcRef,
    U: RootedGcRefImpl<T> + Deref<Target = T>,
{
}

/// An error returned when attempting to allocate a GC-managed object, but the
/// GC heap is out of memory.
///
/// This error wraps an inner `T` value -- which is the host value, if any, that
/// was passed to [`ExternRef::new`][crate::ExternRef::new] -- and you can
/// recover this value via the
/// [`into_inner`][crate::GcHeapOutOfMemory::into_inner] method. This lets you
/// try to allocate the `externref` again, after performing a GC to hopefully
/// free up space in the heap, or otherwise do whatever you want with the inner
/// value.
///
/// For errors that occur when attempting to allocate non-`externref` objects
/// when the GC heap is at capacity, the `T` type parameter is just the unit
/// type `()`.
pub struct GcHeapOutOfMemory<T> {
    inner: T,
}

impl<T> std::fmt::Debug for GcHeapOutOfMemory<T> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        std::fmt::Display::fmt(self, f)
    }
}

impl<T> std::fmt::Display for GcHeapOutOfMemory<T> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "GC heap out of memory")
    }
}

impl<T> std::error::Error for GcHeapOutOfMemory<T> {}

impl<T> GcHeapOutOfMemory<T> {
    pub(crate) fn new(inner: T) -> Self {
        Self { inner }
    }

    /// Recover this error's inner host value.
    pub fn into_inner(self) -> T {
        self.inner
    }
}