Vendor things

third-party/vendor/hashbrown-0.12.3/src/scopeguard.rs

@@ -0,0 +1,74 @@
+// Extracted from the scopeguard crate
+use core::{
+    mem,
+    ops::{Deref, DerefMut},
+    ptr,
+};
+
+pub struct ScopeGuard<T, F>
+where
+    F: FnMut(&mut T),
+{
+    dropfn: F,
+    value: T,
+}
+
+#[inline]
+pub fn guard<T, F>(value: T, dropfn: F) -> ScopeGuard<T, F>
+where
+    F: FnMut(&mut T),
+{
+    ScopeGuard { dropfn, value }
+}
+
+impl<T, F> ScopeGuard<T, F>
+where
+    F: FnMut(&mut T),
+{
+    #[inline]
+    pub fn into_inner(guard: Self) -> T {
+        // Cannot move out of Drop-implementing types, so
+        // ptr::read the value and forget the guard.
+        unsafe {
+            let value = ptr::read(&guard.value);
+            // read the closure so that it is dropped, and assign it to a local
+            // variable to ensure that it is only dropped after the guard has
+            // been forgotten. (In case the Drop impl of the closure, or that
+            // of any consumed captured variable, panics).
+            let _dropfn = ptr::read(&guard.dropfn);
+            mem::forget(guard);
+            value
+        }
+    }
+}
+
+impl<T, F> Deref for ScopeGuard<T, F>
+where
+    F: FnMut(&mut T),
+{
+    type Target = T;
+    #[inline]
+    fn deref(&self) -> &T {
+        &self.value
+    }
+}
+
+impl<T, F> DerefMut for ScopeGuard<T, F>
+where
+    F: FnMut(&mut T),
+{
+    #[inline]
+    fn deref_mut(&mut self) -> &mut T {
+        &mut self.value
+    }
+}
+
+impl<T, F> Drop for ScopeGuard<T, F>
+where
+    F: FnMut(&mut T),
+{
+    #[inline]
+    fn drop(&mut self) {
+        (self.dropfn)(&mut self.value);
+    }
+}