From 8f3d3b91b208f18ff09108722e899a4f7b2b9ecb Mon Sep 17 00:00:00 2001
From: Tim Cheeseman <tim@spec-trust.com>
Date: Tue, 10 Dec 2024 13:36:13 -0500
Subject: [PATCH] Wrap vref in opaque type to allow exhaustive matching on
 Value enum outside of crate. Addresses #502

---
 src/state/raw.rs |  8 +++++---
 src/value.rs     | 17 +++++++++++------
 2 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/src/state/raw.rs b/src/state/raw.rs
index 0731f846..9bafd39b 100644
--- a/src/state/raw.rs
+++ b/src/state/raw.rs
@@ -31,7 +31,7 @@ use crate::util::{
     pop_error, push_internal_userdata, push_string, push_table, rawset_field, safe_pcall, safe_xpcall,
     short_type_name, StackGuard, WrappedFailure,
 };
-use crate::value::{Nil, Value};
+use crate::value::{Nil, Other, Value};
 
 use super::extra::ExtraData;
 use super::{Lua, LuaOptions, WeakLua};
@@ -585,7 +585,7 @@ impl RawLua {
                 let protect = !self.unlikely_memory_error();
                 push_internal_userdata(state, WrappedFailure::Error(*err.clone()), protect)?;
             }
-            Value::Other(vref) => self.push_ref(vref),
+            Value::Other(Other { inner: vref }) => self.push_ref(vref),
         }
         Ok(())
     }
@@ -689,7 +689,9 @@ impl RawLua {
 
             _ => {
                 ffi::lua_xpush(state, self.ref_thread(), idx);
-                Value::Other(self.pop_ref_thread())
+                Value::Other(Other {
+                    inner: self.pop_ref_thread(),
+                })
             }
         }
     }
diff --git a/src/value.rs b/src/value.rs
index 6c81ee55..5237697e 100644
--- a/src/value.rs
+++ b/src/value.rs
@@ -67,8 +67,13 @@ pub enum Value {
     /// `Error` is a special builtin userdata type. When received from Lua it is implicitly cloned.
     Error(Box<Error>),
     /// Any other value not known to mlua (eg. LuaJIT CData).
-    #[allow(private_interfaces)]
-    Other(ValueRef),
+    Other(Other),
+}
+
+/// Opaque wrapper to allow matching on `Value::Other` variant
+#[derive(Clone)]
+pub struct Other {
+    pub(crate) inner: ValueRef,
 }
 
 pub use self::Value::Nil;
@@ -140,7 +145,7 @@ impl Value {
             | Value::Function(Function(vref))
             | Value::Thread(Thread(vref, ..))
             | Value::UserData(AnyUserData(vref))
-            | Value::Other(vref) => vref.to_pointer(),
+            | Value::Other(Other { inner: vref }) => vref.to_pointer(),
             #[cfg(feature = "luau")]
             Value::Buffer(crate::Buffer(vref)) => vref.to_pointer(),
             _ => ptr::null(),
@@ -179,7 +184,7 @@ impl Value {
             | Value::Function(Function(vref))
             | Value::Thread(Thread(vref, ..))
             | Value::UserData(AnyUserData(vref))
-            | Value::Other(vref) => unsafe { invoke_to_string(vref) },
+            | Value::Other(Other { inner: vref }) => unsafe { invoke_to_string(vref) },
             #[cfg(feature = "luau")]
             Value::Buffer(crate::Buffer(vref)) => unsafe { invoke_to_string(vref) },
             Value::Error(err) => Ok(err.to_string()),
@@ -565,7 +570,7 @@ impl Value {
             buf @ Value::Buffer(_) => write!(fmt, "buffer: {:?}", buf.to_pointer()),
             Value::Error(e) if recursive => write!(fmt, "{e:?}"),
             Value::Error(_) => write!(fmt, "error"),
-            Value::Other(v) => write!(fmt, "other: {:?}", v.to_pointer()),
+            Value::Other(Other { inner: v }) => write!(fmt, "other: {:?}", v.to_pointer()),
         }
     }
 }
@@ -592,7 +597,7 @@ impl fmt::Debug for Value {
             #[cfg(feature = "luau")]
             Value::Buffer(buf) => write!(fmt, "{buf:?}"),
             Value::Error(e) => write!(fmt, "Error({e:?})"),
-            Value::Other(v) => write!(fmt, "Other({v:?})"),
+            Value::Other(v) => write!(fmt, "Other({0:?})", v.inner),
         }
     }
 }