1 files changed, 85 insertions, 0 deletions
diff --git a/third_party/rust/jsparagus-ast/src/arena.rs b/third_party/rust/jsparagus-ast/src/arena.rs
new file mode 100644
index 0000000000..5c1abdbe86
--- /dev/null
+++ b/third_party/rust/jsparagus-ast/src/arena.rs
@@ -0,0 +1,85 @@
+use bumpalo::Bump;
+
+use std::{
+    self,
+    fmt::{self, Debug, Formatter},
+    ops, ptr,
+};
+
+pub use bumpalo::collections::{String, Vec};
+
+pub struct Box<'alloc, T: ?Sized>(&'alloc mut T);
+
+impl<'alloc, T> Box<'alloc, T> {
+    pub fn unbox(self) -> T {
+        // This pointer read is safe because the reference `self.0` is
+        // guaranteed to be unique--not just now, but we're guaranteed it's not
+        // borrowed from some other reference. This in turn is because we never
+        // construct an alloc::Box with a borrowed reference, only with a fresh
+        // one just allocated from a Bump.
+        unsafe { ptr::read(self.0 as *mut T) }
+    }
+}
+
+impl<'alloc, T: ?Sized> ops::Deref for Box<'alloc, T> {
+    type Target = T;
+
+    fn deref(&self) -> &T {
+        self.0
+    }
+}
+
+impl<'alloc, T: ?Sized> ops::DerefMut for Box<'alloc, T> {
+    fn deref_mut(&mut self) -> &mut T {
+        self.0
+    }
+}
+
+impl<'alloc, T: ?Sized> Debug for Box<'alloc, T>
+where
+    T: Debug,
+{
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+impl<'alloc, T> PartialEq for Box<'alloc, T>
+where
+    T: PartialEq<T> + ?Sized,
+{
+    fn eq(&self, other: &Box<'alloc, T>) -> bool {
+        PartialEq::eq(&**self, &**other)
+    }
+
+    fn ne(&self, other: &Box<'alloc, T>) -> bool {
+        PartialEq::ne(&**self, &**other)
+    }
+}
+
+pub fn alloc<'alloc, T>(allocator: &'alloc Bump, value: T) -> Box<'alloc, T> {
+    Box(allocator.alloc(value))
+}
+
+pub fn alloc_with<'alloc, F, T>(allocator: &'alloc Bump, gen: F) -> Box<'alloc, T>
+where
+    F: FnOnce() -> T,
+{
+    Box(allocator.alloc_with(gen))
+}
+
+pub fn alloc_str<'alloc>(allocator: &'alloc Bump, value: &str) -> &'alloc str {
+    String::from_str_in(value, allocator).into_bump_str()
+}
+
+pub fn map_vec<'alloc, A, B>(
+    source: &mut Vec<A>,
+    mut map_fn: impl FnMut(&mut A) -> B,
+    allocator: &'alloc Bump,
+) -> Vec<'alloc, B> {
+    let mut out = Vec::with_capacity_in(source.len(), allocator);
+    for item in source {
+        out.push(map_fn(item));
+    }
+    out
+}