moved all crates into seperate folder + related path fixes

crates/roc_std/src/storage.rs

@@ -0,0 +1,66 @@
+use core::num::NonZeroIsize;
+
+/// # Safety
+///
+/// isize::MIN is definitely not zero. This can become
+/// https://doc.rust-lang.org/std/num/struct.NonZeroIsize.html#associatedconstant.MIN
+/// once it has been stabilized.
+const REFCOUNT_1: NonZeroIsize = unsafe { NonZeroIsize::new_unchecked(isize::MIN) };
+
+const _ASSERT_STORAGE_SIZE: () =
+    assert!(std::mem::size_of::<isize>() == std::mem::size_of::<Storage>());
+
+#[derive(Clone, Copy, Debug)]
+pub enum Storage {
+    Readonly,
+    ReferenceCounted(NonZeroIsize),
+}
+
+impl Storage {
+    pub fn new_reference_counted() -> Self {
+        Self::ReferenceCounted(REFCOUNT_1)
+    }
+
+    /// Increment the reference count.
+    pub fn increment_reference_count(&mut self) {
+        match self {
+            Storage::Readonly => {
+                // Do nothing.
+            }
+            Storage::ReferenceCounted(rc) => {
+                let new_rc = rc.get() + 1;
+                if let Some(new_rc) = NonZeroIsize::new(new_rc) {
+                    *self = Storage::ReferenceCounted(new_rc);
+                } else {
+                    *self = Storage::Readonly;
+                }
+            }
+        }
+    }
+
+    /// Decrease the reference count.
+    ///
+    /// Returns `true` once there are no more references left.
+    pub fn decrease(&mut self) -> bool {
+        match self {
+            Storage::Readonly => false,
+            Storage::ReferenceCounted(rc) => {
+                if *rc == REFCOUNT_1 {
+                    true
+                } else {
+                    *rc = NonZeroIsize::new(rc.get() - 1).expect("A reference count was decremented all the way to zero, which should never happen.");
+
+                    false
+                }
+            }
+        }
+    }
+
+    pub fn is_readonly(&self) -> bool {
+        matches!(self, Self::Readonly)
+    }
+
+    pub fn is_unique(&self) -> bool {
+        matches!(self, Self::ReferenceCounted(REFCOUNT_1))
+    }
+}