Rust Port: MetaCall Handle implement Send+Sync and document it (#707)

* Rust Port: MetaCall Handle implement Send+Sync and document it

* bump metacall version to 0.5.7

Author: fahdfady

source/ports/rs_port/Cargo.toml

@@ -1,28 +1,28 @@
-[package]
-authors = ["Mahdi Sharifi <devraymondsh@gmail.com>", "Vicente Eduardo Ferrer Garcia <vic798@gmail.com>", "Swarnim Arun <swarnimarun11@gmail.com>"]
-description = "Call NodeJS, TypeScript, Python, C#, Ruby... functions from Rust (a Rust Port for MetaCall)."
-edition = "2021"
-keywords = ["ffi", "polyglot", "metacall", "inter-language", "polyglot-programming"]
-license = "Apache-2.0"
-name = "metacall"
-readme = "README.md"
-repository = "https://github.com/metacall/core/tree/develop/source/ports/rs_port"
-version = "0.5.6"
-
-[lib]
-crate-type = ["lib"]
-doctest = false
-name = "metacall"
-path = "src/lib.rs"
-
-[dependencies]
-metacall-inline = { version = "0.2.0", path = "./inline" }
-
-[build-dependencies]
-metacall-sys = { version = "0.1.4", path = "./sys" }
-
-[workspace]
-members = [
-    "inline",
-    "sys",
-]
+[package]
+authors = ["Mahdi Sharifi <devraymondsh@gmail.com>", "Vicente Eduardo Ferrer Garcia <vic798@gmail.com>", "Swarnim Arun <swarnimarun11@gmail.com>"]
+description = "Call NodeJS, TypeScript, Python, C#, Ruby... functions from Rust (a Rust Port for MetaCall)."
+edition = "2021"
+keywords = ["ffi", "polyglot", "metacall", "inter-language", "polyglot-programming"]
+license = "Apache-2.0"
+name = "metacall"
+readme = "README.md"
+repository = "https://github.com/metacall/core/tree/develop/source/ports/rs_port"
+version = "0.5.7"
+
+[lib]
+crate-type = ["lib"]
+doctest = false
+name = "metacall"
+path = "src/lib.rs"
+
+[dependencies]
+metacall-inline = { version = "0.2.0", path = "./inline" }
+
+[build-dependencies]
+metacall-sys = { version = "0.1.4", path = "./sys" }
+
+[workspace]
+members = [
+    "inline",
+    "sys",
+]

source/ports/rs_port/src/load.rs

@@ -68,8 +68,16 @@ impl fmt::Display for Tag {
     }
 }
 
+/// A MetaCall Handle is basically a C Pointer, One can pass it to when loading a script
+/// (pass it to [[from_single_file]] for example) to keep the script in a local scope related to
+/// this specific [[Handle]]
+/// [[Handle]] implements Send + Sync traits because we are sure 100% and guarantee developers that
+/// it is thread-safe. The Handle is a read-only pointer so there is no problem here.
 pub struct Handle(*mut c_void);
 
+unsafe impl Send for Handle {}
+unsafe impl Sync for Handle {}
+
 impl Handle {
     pub fn new() -> Self {
         Self(null_mut())