Unnamed repository; edit this file 'description' to name the repository.
Diffstat (limited to 'crates/hir-ty/src/mir.rs')
| -rw-r--r-- | crates/hir-ty/src/mir.rs | 61 |
1 files changed, 14 insertions, 47 deletions
diff --git a/crates/hir-ty/src/mir.rs b/crates/hir-ty/src/mir.rs index 494f1850b8..cfaef2a392 100644 --- a/crates/hir-ty/src/mir.rs +++ b/crates/hir-ty/src/mir.rs @@ -659,66 +659,33 @@ pub enum BorrowKind { /// We can also report errors with this kind of borrow differently. Shallow, - /// Data must be immutable but not aliasable. This kind of borrow - /// cannot currently be expressed by the user and is used only in - /// implicit closure bindings. It is needed when the closure is - /// borrowing or mutating a mutable referent, e.g.: - /// ``` - /// let mut z = 3; - /// let x: &mut isize = &mut z; - /// let y = || *x += 5; - /// ``` - /// If we were to try to translate this closure into a more explicit - /// form, we'd encounter an error with the code as written: - /// ```compile_fail,E0594 - /// struct Env<'a> { x: &'a &'a mut isize } - /// let mut z = 3; - /// let x: &mut isize = &mut z; - /// let y = (&mut Env { x: &x }, fn_ptr); // Closure is pair of env and fn - /// fn fn_ptr(env: &mut Env) { **env.x += 5; } - /// ``` - /// This is then illegal because you cannot mutate an `&mut` found - /// in an aliasable location. To solve, you'd have to translate with - /// an `&mut` borrow: - /// ```compile_fail,E0596 - /// struct Env<'a> { x: &'a mut &'a mut isize } - /// let mut z = 3; - /// let x: &mut isize = &mut z; - /// let y = (&mut Env { x: &mut x }, fn_ptr); // changed from &x to &mut x - /// fn fn_ptr(env: &mut Env) { **env.x += 5; } - /// ``` - /// Now the assignment to `**env.x` is legal, but creating a - /// mutable pointer to `x` is not because `x` is not mutable. We - /// could fix this by declaring `x` as `let mut x`. This is ok in - /// user code, if awkward, but extra weird for closures, since the - /// borrow is hidden. - /// - /// So we introduce a "unique imm" borrow -- the referent is - /// immutable, but not aliasable. This solves the problem. For - /// simplicity, we don't give users the way to express this - /// borrow, it's just used when translating closures. - Unique, - /// Data is mutable and not aliasable. - Mut { - /// `true` if this borrow arose from method-call auto-ref - /// (i.e., `adjustment::Adjust::Borrow`). - allow_two_phase_borrow: bool, - }, + Mut { kind: MutBorrowKind }, +} + +#[derive(Debug, PartialEq, Eq, Clone, Copy, PartialOrd, Ord)] +pub enum MutBorrowKind { + Default, + /// This borrow arose from method-call auto-ref + /// (i.e., adjustment::Adjust::Borrow). + TwoPhasedBorrow, + /// Data must be immutable but not aliasable. This kind of borrow cannot currently + /// be expressed by the user and is used only in implicit closure bindings. + ClosureCapture, } impl BorrowKind { fn from_hir(m: hir_def::type_ref::Mutability) -> Self { match m { hir_def::type_ref::Mutability::Shared => BorrowKind::Shared, - hir_def::type_ref::Mutability::Mut => BorrowKind::Mut { allow_two_phase_borrow: false }, + hir_def::type_ref::Mutability::Mut => BorrowKind::Mut { kind: MutBorrowKind::Default }, } } fn from_chalk(m: Mutability) -> Self { match m { Mutability::Not => BorrowKind::Shared, - Mutability::Mut => BorrowKind::Mut { allow_two_phase_borrow: false }, + Mutability::Mut => BorrowKind::Mut { kind: MutBorrowKind::Default }, } } } |