Fix the issue of duplicate unique ID for atoms using newtype.

The MergeFunctionsPass in LLVM merges identical functions (https://rust.godbolt.org/z/3nnr9nMne), resulting in the same function addresses.

packages/fermi/src/atoms/atom.rs

@@ -1,21 +1,21 @@
 use crate::{AtomId, AtomRoot, Readable, Writable};
 
-pub type Atom<T> = fn(AtomBuilder) -> T;
+pub struct Atom<T>(pub fn(AtomBuilder) -> T);
 pub struct AtomBuilder;
 
-impl<V> Readable<V> for Atom<V> {
+impl<V> Readable<V> for &'static Atom<V> {
     fn read(&self, _root: AtomRoot) -> Option<V> {
         todo!()
     }
     fn init(&self) -> V {
-        (*self)(AtomBuilder)
+        self.0(AtomBuilder)
     }
     fn unique_id(&self) -> AtomId {
-        *self as *const ()
+        *self as *const Atom<V> as *const ()
     }
 }
 
-impl<V> Writable<V> for Atom<V> {
+impl<V> Writable<V> for &'static Atom<V> {
     fn write(&self, _root: AtomRoot, _value: V) {
         todo!()
     }
@@ -23,6 +23,22 @@ impl<V> Writable<V> for Atom<V> {
 
 #[test]
 fn atom_compiles() {
-    static TEST_ATOM: Atom<&str> = |_| "hello";
-    dbg!(TEST_ATOM.init());
+    static TEST_ATOM: Atom<&str> = Atom(|_| "hello");
+    dbg!((&TEST_ATOM).init());
+}
+
+#[test]
+fn atom_is_unique() {
+    static TEST_ATOM_1: Atom<&str> = Atom(|_| "hello");
+    static TEST_ATOM_2: Atom<&str> = Atom(|_| "hello");
+    assert_eq!((&TEST_ATOM_1).unique_id(), (&TEST_ATOM_1).unique_id());
+    assert_ne!((&TEST_ATOM_1).unique_id(), (&TEST_ATOM_2).unique_id());
+}
+
+#[test]
+fn atom_is_unique_2() {
+    struct S(String);
+    static TEST_ATOM_1: Atom<Vec<S>> = Atom(|_| Vec::new());
+    static TEST_ATOM_2: Atom<Vec<String>> = Atom(|_| Vec::new());
+    assert_ne!((&TEST_ATOM_1).unique_id(), (&TEST_ATOM_2).unique_id());
 }