Unnamed repository; edit this file 'description' to name the repository.
Diffstat (limited to 'crates/hir-ty/src/utils.rs')
| -rw-r--r-- | crates/hir-ty/src/utils.rs | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/crates/hir-ty/src/utils.rs b/crates/hir-ty/src/utils.rs index efc0ac2bf8..7dd73f1e7a 100644 --- a/crates/hir-ty/src/utils.rs +++ b/crates/hir-ty/src/utils.rs @@ -25,6 +25,26 @@ use crate::{ mir::pad16, }; +/// SAFETY: `old_pointer` must be valid for unique writes +pub(crate) unsafe fn unsafe_update_eq<T>(old_pointer: *mut T, new_value: T) -> bool +where + T: PartialEq, +{ + // SAFETY: Caller obligation + let old_ref: &mut T = unsafe { &mut *old_pointer }; + + if *old_ref != new_value { + *old_ref = new_value; + true + } else { + // Subtle but important: Eq impls can be buggy or define equality + // in surprising ways. If it says that the value has not changed, + // we do not modify the existing value, and thus do not have to + // update the revision, as downstream code will not see the new value. + false + } +} + pub(crate) fn fn_traits(lang_items: &LangItems) -> impl Iterator<Item = TraitId> + '_ { [lang_items.Fn, lang_items.FnMut, lang_items.FnOnce].into_iter().flatten() } |