feat!: introduce tree-sitter-language crate for grammar crates to depend on

Co-authored-by: Conrad <conrad@zed.dev>
Co-authored-by: Marshall <marshall@zed.dev>
Co-authored-by: Amaan Qureshi <amaanq12@gmail.com>

lib/language/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "tree-sitter-language"
+description = "The tree-sitter Language type, used by the library and by language implementations"
+version = "0.1.0"
+authors.workspace = true
+edition.workspace = true
+rust-version.workspace = true
+homepage.workspace = true
+repository.workspace = true
+license.workspace = true
+keywords.workspace = true
+
+[lib]
+path = "language.rs"

lib/language/language.rs

@@ -0,0 +1,20 @@
+/// LanguageFn wraps a C function that returns a pointer to a tree-sitter grammer.
+#[repr(transparent)]
+pub struct LanguageFn(unsafe extern "C" fn() -> *const ());
+
+impl LanguageFn {
+    /// Creates a `LanguageFn`.
+    ///
+    /// # Safety
+    ///
+    /// Only call this with language functions generated from grammars
+    /// by the Tree-sitter CLI.
+    pub const unsafe fn from_raw(f: unsafe extern "C" fn() -> *const ()) -> Self {
+        Self(f)
+    }
+
+    /// Gets the function wrapped by this `LanguageFn`.
+    pub const fn into_raw(self) -> unsafe extern "C" fn() -> *const () {
+        self.0
+    }
+}