impl `ToLua` and `FromLua` for `HashSet` and `BTreeSet`

src/conversion.rs

@@ -1,4 +1,4 @@
-use std::collections::{BTreeMap, HashMap};
+use std::collections::{BTreeMap, BTreeSet, HashMap, HashSet};
 use std::ffi::{CStr, CString};
 use std::hash::{BuildHasher, Hash};
 use std::string::String as StdString;
@@ -481,6 +481,56 @@ impl<'lua, K: Ord + FromLua<'lua>, V: FromLua<'lua>> FromLua<'lua> for BTreeMap<
     }
 }
 
+impl<'lua, T: Eq + Hash + ToLua<'lua>, S: BuildHasher> ToLua<'lua> for HashSet<T, S> {
+    fn to_lua(self, lua: &'lua Lua) -> Result<Value<'lua>> {
+        Ok(Value::Table(lua.create_table_from(
+            self.into_iter().map(|val| (val, true)),
+        )?))
+    }
+}
+
+impl<'lua, T: Eq + Hash + FromLua<'lua>, S: BuildHasher + Default> FromLua<'lua> for HashSet<T, S> {
+    fn from_lua(value: Value<'lua>, _: &'lua Lua) -> Result<Self> {
+        if let Value::Table(table) = value {
+            table
+                .pairs::<T, Value<'lua>>()
+                .map(|res| res.map(|(k, _)| k))
+                .collect()
+        } else {
+            Err(Error::FromLuaConversionError {
+                from: value.type_name(),
+                to: "HashSet",
+                message: Some("expected table".to_string()),
+            })
+        }
+    }
+}
+
+impl<'lua, T: Ord + ToLua<'lua>> ToLua<'lua> for BTreeSet<T> {
+    fn to_lua(self, lua: &'lua Lua) -> Result<Value<'lua>> {
+        Ok(Value::Table(lua.create_table_from(
+            self.into_iter().map(|val| (val, true)),
+        )?))
+    }
+}
+
+impl<'lua, T: Ord + FromLua<'lua>> FromLua<'lua> for BTreeSet<T> {
+    fn from_lua(value: Value<'lua>, _: &'lua Lua) -> Result<Self> {
+        if let Value::Table(table) = value {
+            table
+                .pairs::<T, Value<'lua>>()
+                .map(|res| res.map(|(k, _)| k))
+                .collect()
+        } else {
+            Err(Error::FromLuaConversionError {
+                from: value.type_name(),
+                to: "BTreeSet",
+                message: Some("expected table".to_string()),
+            })
+        }
+    }
+}
+
 impl<'lua, T: ToLua<'lua>> ToLua<'lua> for Option<T> {
     fn to_lua(self, lua: &'lua Lua) -> Result<Value<'lua>> {
         match self {