charon_lib/ast/
expressions.rs

1//! Implements expressions: paths, operands, rvalues, lvalues
2
3use crate::ast::*;
4use derive_generic_visitor::{Drive, DriveMut};
5use macros::{EnumAsGetters, EnumIsA, EnumToGetters, VariantIndexArity, VariantName};
6use serde::{Deserialize, Serialize};
7use std::vec::Vec;
8
9#[derive(Debug, PartialEq, Eq, Clone, Serialize, Deserialize, Drive, DriveMut)]
10pub struct Place {
11    pub kind: PlaceKind,
12    pub ty: Ty,
13}
14
15#[derive(
16    Debug,
17    PartialEq,
18    Eq,
19    Clone,
20    EnumIsA,
21    EnumAsGetters,
22    EnumToGetters,
23    Serialize,
24    Deserialize,
25    Drive,
26    DriveMut,
27)]
28#[charon::variants_prefix("Place")]
29pub enum PlaceKind {
30    /// A local variable in a function body.
31    Local(LocalId),
32    /// A subplace of a place.
33    Projection(Box<Place>, ProjectionElem),
34    /// A global (const or static).
35    /// Not present in MIR; introduced in [simplify_constants.rs].
36    Global(GlobalDeclRef),
37}
38
39/// Note that we don't have the equivalent of "downcasts".
40/// Downcasts are actually necessary, for instance when initializing enumeration
41/// values: the value is initially `Bottom`, and we need a way of knowing the
42/// variant.
43/// For example:
44/// `((_0 as Right).0: T2) = move _1;`
45/// In MIR, downcasts always happen before field projections: in our internal
46/// language, we thus merge downcasts and field projections.
47#[derive(
48    Debug,
49    PartialEq,
50    Eq,
51    Clone,
52    EnumIsA,
53    EnumAsGetters,
54    EnumToGetters,
55    VariantName,
56    Serialize,
57    Deserialize,
58    Drive,
59    DriveMut,
60)]
61pub enum ProjectionElem {
62    /// Dereference a shared/mutable reference, a box, or a raw pointer.
63    Deref,
64    /// Projection from ADTs (variants, structures).
65    /// We allow projections to be used as left-values and right-values.
66    /// We should never have projections to fields of symbolic variants (they
67    /// should have been expanded before through a match).
68    Field(FieldProjKind, FieldId),
69    /// A built-in pointer (a reference, raw pointer, or `Box`) in Rust is always a fat pointer: it
70    /// contains an address and metadata for the pointed-to place. This metadata is empty for sized
71    /// types, it's the length for slices, and the vtable for `dyn Trait`.
72    ///
73    /// We consider such pointers to be like a struct with two fields; this represent access to the
74    /// metadata "field".
75    PtrMetadata,
76    /// MIR imposes that the argument to an index projection be a local variable, meaning
77    /// that even constant indices into arrays are let-bound as separate variables.
78    /// We **eliminate** this variant in a micro-pass for LLBC.
79    #[charon::rename("ProjIndex")]
80    Index {
81        offset: Box<Operand>,
82        #[drive(skip)]
83        from_end: bool,
84    },
85    /// Take a subslice of a slice or array. If `from_end` is `true` this is
86    /// `slice[from..slice.len() - to]`, otherwise this is `slice[from..to]`.
87    /// We **eliminate** this variant in a micro-pass for LLBC.
88    Subslice {
89        from: Box<Operand>,
90        to: Box<Operand>,
91        #[drive(skip)]
92        from_end: bool,
93    },
94}
95
96#[derive(
97    Debug,
98    PartialEq,
99    Eq,
100    Copy,
101    Clone,
102    EnumIsA,
103    EnumAsGetters,
104    Serialize,
105    Deserialize,
106    Drive,
107    DriveMut,
108)]
109#[charon::variants_prefix("Proj")]
110pub enum FieldProjKind {
111    Adt(TypeDeclId, Option<VariantId>),
112    /// If we project from a tuple, the projection kind gives the arity of the tuple.
113    #[drive(skip)]
114    Tuple(usize),
115}
116
117#[derive(
118    Debug,
119    PartialEq,
120    Eq,
121    Copy,
122    Clone,
123    EnumIsA,
124    EnumAsGetters,
125    Serialize,
126    Deserialize,
127    Drive,
128    DriveMut,
129)]
130#[charon::variants_prefix("B")]
131pub enum BorrowKind {
132    Shared,
133    Mut,
134    /// See <https://doc.rust-lang.org/beta/nightly-rustc/rustc_middle/mir/enum.MutBorrowKind.html#variant.TwoPhaseBorrow>
135    /// and <https://rustc-dev-guide.rust-lang.org/borrow_check/two_phase_borrows.html>
136    TwoPhaseMut,
137    /// Those are typically introduced when using guards in matches, to make sure guards don't
138    /// change the variant of an enum value while me match over it.
139    ///
140    /// See <https://doc.rust-lang.org/beta/nightly-rustc/rustc_middle/mir/enum.FakeBorrowKind.html#variant.Shallow>.
141    Shallow,
142    /// Data must be immutable but not aliasable. In other words you can't mutate the data but you
143    /// can mutate *through it*, e.g. if it points to a `&mut T`. This is only used in closure
144    /// captures, e.g.
145    /// ```rust,ignore
146    /// let mut z = 3;
147    /// let x: &mut isize = &mut z;
148    /// let y = || *x += 5;
149    /// ```
150    /// Here the captured variable can't be `&mut &mut x` since the `x` binding is not mutable, yet
151    /// we must be able to mutate what it points to.
152    ///
153    /// See <https://doc.rust-lang.org/beta/nightly-rustc/rustc_middle/mir/enum.MutBorrowKind.html#variant.ClosureCapture>.
154    UniqueImmutable,
155}
156
157/// Unary operation
158#[derive(
159    Debug, PartialEq, Eq, Clone, EnumIsA, VariantName, Serialize, Deserialize, Drive, DriveMut,
160)]
161#[charon::rename("Unop")]
162pub enum UnOp {
163    Not,
164    /// This can overflow, for `-i::MIN`.
165    #[drive(skip)]
166    Neg(OverflowMode),
167    /// Casts are rvalues in MIR, but we treat them as unops.
168    Cast(CastKind),
169}
170
171/// Nullary operation
172#[derive(
173    Debug, PartialEq, Eq, Clone, EnumIsA, VariantName, Serialize, Deserialize, Drive, DriveMut,
174)]
175#[charon::rename("Nullop")]
176pub enum NullOp {
177    SizeOf,
178    AlignOf,
179    #[drive(skip)]
180    OffsetOf(Vec<(usize, FieldId)>),
181    UbChecks,
182}
183
184/// For all the variants: the first type gives the source type, the second one gives
185/// the destination type.
186#[derive(
187    Debug, PartialEq, Eq, Clone, EnumIsA, VariantName, Serialize, Deserialize, Drive, DriveMut,
188)]
189#[charon::variants_prefix("Cast")]
190pub enum CastKind {
191    /// Conversion between types in `{Integer, Bool}`
192    /// Remark: for now we don't support conversions with Char.
193    Scalar(LiteralTy, LiteralTy),
194    RawPtr(Ty, Ty),
195    FnPtr(Ty, Ty),
196    /// [Unsize coercion](https://doc.rust-lang.org/std/ops/trait.CoerceUnsized.html). This is
197    /// either `[T; N]` -> `[T]` or `T: Trait` -> `dyn Trait` coercions, behind a pointer
198    /// (reference, `Box`, or other type that implements `CoerceUnsized`).
199    ///
200    /// The special case of `&[T; N]` -> `&[T]` coercion is caught by `UnOp::ArrayToSlice`.
201    Unsize(Ty, Ty, UnsizingMetadata),
202    /// Reinterprets the bits of a value of one type as another type, i.e. exactly what
203    /// [`std::mem::transmute`] does.
204    Transmute(Ty, Ty),
205    /// Converts a receiver type with `dyn Trait<...>` to a concrete type `T`, used in vtable method shims.
206    /// Valid conversions are references, raw pointers, and (optionally) boxes:
207    /// - `&[mut] dyn Trait<...>` -> `&[mut] T`
208    /// - `*[mut] dyn Trait<...>` -> `*[mut] T`
209    /// - `Box<dyn Trait<...>>` -> `Box<T>` when no `--raw-boxes`
210    ///
211    /// For possible receivers, see: <https://doc.rust-lang.org/reference/items/traits.html#dyn-compatibility>.
212    /// Other receivers, e.g., `Rc` should be unpacked before the cast and re-boxed after.
213    /// FIXME(ssyram): but this is not implemented yet, namely, there may still be
214    ///     something like `Rc<dyn Trait<...>> -> Rc<T>` in the types.
215    Concretize(Ty, Ty),
216}
217
218#[derive(
219    Debug, PartialEq, Eq, Clone, EnumIsA, VariantName, Serialize, Deserialize, Drive, DriveMut,
220)]
221#[charon::variants_prefix("Meta")]
222pub enum UnsizingMetadata {
223    Length(ConstGeneric),
224    VTablePtr(TraitRef),
225    Unknown,
226}
227
228#[derive(Debug, PartialEq, Eq, Copy, Clone, Serialize, Deserialize)]
229#[charon::variants_prefix("O")]
230pub enum OverflowMode {
231    /// If this operation overflows, it panics. Only exists in debug mode, for instance in
232    /// `a + b`, and is introduced by the `remove_dynamic_checks` pass.
233    Panic,
234    /// If this operation overflows, it UBs, for instance in `core::num::unchecked_add`.
235    UB,
236    /// If this operation overflows, it wraps around, for instance in `core::num::wrapping_add`,
237    /// or `a + b` in release mode.
238    Wrap,
239}
240
241/// Binary operations.
242#[derive(
243    Debug, PartialEq, Eq, Copy, Clone, EnumIsA, VariantName, Serialize, Deserialize, Drive, DriveMut,
244)]
245#[charon::rename("Binop")]
246pub enum BinOp {
247    BitXor,
248    BitAnd,
249    BitOr,
250    Eq,
251    Lt,
252    Le,
253    Ne,
254    Ge,
255    Gt,
256    #[drive(skip)]
257    Add(OverflowMode),
258    #[drive(skip)]
259    Sub(OverflowMode),
260    #[drive(skip)]
261    Mul(OverflowMode),
262    #[drive(skip)]
263    Div(OverflowMode),
264    #[drive(skip)]
265    Rem(OverflowMode),
266    /// Returns `(result, did_overflow)`, where `result` is the result of the operation with
267    /// wrapping semantics, and `did_overflow` is a boolean that indicates whether the operation
268    /// overflowed. This operation does not fail.
269    AddChecked,
270    /// Like `AddChecked`.
271    SubChecked,
272    /// Like `AddChecked`.
273    MulChecked,
274    /// Fails if the shift is bigger than the bit-size of the type.
275    #[drive(skip)]
276    Shl(OverflowMode),
277    /// Fails if the shift is bigger than the bit-size of the type.
278    #[drive(skip)]
279    Shr(OverflowMode),
280    /// `BinOp(Offset, ptr, n)` for `ptr` a pointer to type `T` offsets `ptr` by `n * size_of::<T>()`.
281    Offset,
282    /// `BinOp(Cmp, a, b)` returns `-1u8` if `a < b`, `0u8` if `a == b`, and `1u8` if `a > b`.
283    Cmp,
284}
285
286#[derive(
287    Debug,
288    PartialEq,
289    Eq,
290    Clone,
291    EnumIsA,
292    EnumToGetters,
293    EnumAsGetters,
294    VariantName,
295    Serialize,
296    Deserialize,
297    Drive,
298    DriveMut,
299)]
300pub enum Operand {
301    Copy(Place),
302    Move(Place),
303    /// Constant value (including constant and static variables)
304    #[charon::rename("Constant")]
305    Const(Box<ConstantExpr>),
306}
307
308/// A function identifier. See [crate::ullbc_ast::Terminator]
309#[derive(
310    Debug,
311    Clone,
312    PartialEq,
313    Eq,
314    Hash,
315    EnumIsA,
316    EnumAsGetters,
317    VariantName,
318    Serialize,
319    Deserialize,
320    Drive,
321    DriveMut,
322)]
323#[charon::variants_prefix("F")]
324pub enum FunId {
325    /// A "regular" function (function local to the crate, external function
326    /// not treated as a primitive one).
327    Regular(FunDeclId),
328    /// A primitive function, coming from a standard library (for instance:
329    /// `alloc::boxed::Box::new`).
330    /// TODO: rename to "Primitive"
331    #[charon::rename("FBuiltin")]
332    Builtin(BuiltinFunId),
333}
334
335impl From<FunDeclId> for FunId {
336    fn from(id: FunDeclId) -> Self {
337        Self::Regular(id)
338    }
339}
340impl From<BuiltinFunId> for FunId {
341    fn from(id: BuiltinFunId) -> Self {
342        Self::Builtin(id)
343    }
344}
345
346/// An built-in function identifier, identifying a function coming from a
347/// standard library.
348#[derive(
349    Debug,
350    Clone,
351    Copy,
352    PartialEq,
353    Eq,
354    Hash,
355    EnumIsA,
356    EnumAsGetters,
357    VariantName,
358    Serialize,
359    Deserialize,
360    Drive,
361    DriveMut,
362)]
363pub enum BuiltinFunId {
364    /// `alloc::boxed::Box::new`
365    BoxNew,
366    /// Cast an array as a slice.
367    ///
368    /// Converted from `UnOp::ArrayToSlice`
369    ArrayToSliceShared,
370    /// Cast an array as a slice.
371    ///
372    /// Converted from `UnOp::ArrayToSlice`
373    ArrayToSliceMut,
374    /// `repeat(n, x)` returns an array where `x` has been replicated `n` times.
375    ///
376    /// We introduce this when desugaring the `ArrayRepeat` rvalue.
377    ArrayRepeat,
378    /// Converted from indexing `ProjectionElem`s. The signature depends on the parameters. It
379    /// could look like:
380    /// - `fn ArrayIndexShared<T,N>(&[T;N], usize) -> &T`
381    /// - `fn SliceIndexShared<T>(&[T], usize) -> &T`
382    /// - `fn ArraySubSliceShared<T,N>(&[T;N], usize, usize) -> &[T]`
383    /// - `fn SliceSubSliceMut<T>(&mut [T], usize, usize) -> &mut [T]`
384    /// - etc
385    Index(BuiltinIndexOp),
386    /// Build a raw pointer, from a data pointer and metadata. The metadata can be unit, if
387    /// building a thin pointer.
388    ///
389    /// Converted from [AggregateKind::RawPtr]
390    PtrFromParts(RefKind),
391}
392
393/// One of 8 built-in indexing operations.
394#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize, Drive, DriveMut)]
395pub struct BuiltinIndexOp {
396    /// Whether this is a slice or array.
397    #[drive(skip)]
398    pub is_array: bool,
399    /// Whether we're indexing mutably or not. Determines the type ofreference of the input and
400    /// output.
401    pub mutability: RefKind,
402    /// Whether we're indexing a single element or a subrange. If `true`, the function takes
403    /// two indices and the output is a slice; otherwise, the function take one index and the
404    /// output is a reference to a single element.
405    #[drive(skip)]
406    pub is_range: bool,
407}
408
409/// Reference to a function declaration or builtin function.
410#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq, Hash, Drive, DriveMut)]
411pub struct MaybeBuiltinFunDeclRef {
412    pub id: FunId,
413    pub generics: BoxedArgs,
414}
415
416/// Reference to a trait method.
417#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq, Hash, Drive, DriveMut)]
418pub struct TraitMethodRef {
419    pub trait_ref: TraitRef,
420    pub name: TraitItemName,
421    pub generics: BoxedArgs,
422    /// Reference to the method declaration; can be derived from the trait_ref, provided here for
423    /// convenience. The generic args are for the method, not for this function.
424    pub method_decl_id: FunDeclId,
425}
426
427#[derive(
428    Debug, Clone, PartialEq, Eq, EnumAsGetters, Serialize, Deserialize, Drive, DriveMut, Hash,
429)]
430pub enum FnPtrKind {
431    #[charon::rename("FunId")]
432    Fun(FunId),
433    /// If a trait: the reference to the trait and the id of the trait method.
434    /// The fun decl id is not really necessary - we put it here for convenience
435    /// purposes.
436    #[charon::rename("TraitMethod")]
437    Trait(TraitRef, TraitItemName, FunDeclId),
438}
439
440impl From<FunId> for FnPtrKind {
441    fn from(id: FunId) -> Self {
442        Self::Fun(id)
443    }
444}
445impl From<FunDeclId> for FnPtrKind {
446    fn from(id: FunDeclId) -> Self {
447        Self::Fun(id.into())
448    }
449}
450
451#[derive(Debug, PartialEq, Eq, Clone, Serialize, Deserialize, Drive, DriveMut, Hash)]
452pub struct FnPtr {
453    pub kind: Box<FnPtrKind>,
454    pub generics: BoxedArgs,
455}
456
457impl From<FunDeclRef> for FnPtr {
458    fn from(fn_ref: FunDeclRef) -> Self {
459        FnPtr {
460            kind: Box::new(fn_ref.id.into()),
461            generics: fn_ref.generics,
462        }
463    }
464}
465
466/// A constant expression.
467///
468/// Only the [`ConstantExprKind::Literal`] and [`ConstantExprKind::Var`]
469/// cases are left in the final LLBC.
470///
471/// The other cases come from a straight translation from the MIR:
472///
473/// [`ConstantExprKind::Adt`] case:
474/// It is a bit annoying, but rustc treats some ADT and tuple instances as
475/// constants when generating MIR:
476/// - an enumeration with one variant and no fields is a constant.
477/// - a structure with no field is a constant.
478/// - sometimes, Rust stores the initialization of an ADT as a constant
479///   (if all the fields are constant) rather than as an aggregated value
480/// We later desugar those to regular ADTs, see [regularize_constant_adts.rs].
481///
482/// [`ConstantExprKind::Global`] case: access to a global variable. We later desugar it to
483/// a copy of a place global.
484///
485/// [`ConstantExprKind::Ref`] case: reference to a constant value. We later desugar it to a separate
486/// statement.
487///
488/// [`ConstantExprKind::FnPtr`] case: a function pointer (to a top-level function).
489///
490/// Remark:
491/// MIR seems to forbid more complex expressions like paths. For instance,
492/// reading the constant `a.b` is translated to `{ _1 = const a; _2 = (_1.0) }`.
493#[derive(
494    Debug,
495    Hash,
496    PartialEq,
497    Eq,
498    Clone,
499    VariantName,
500    EnumIsA,
501    EnumAsGetters,
502    Serialize,
503    Deserialize,
504    Drive,
505    DriveMut,
506)]
507#[charon::variants_prefix("C")]
508pub enum ConstantExprKind {
509    Literal(Literal),
510    /// In most situations:
511    /// Enumeration with one variant with no fields, structure with
512    /// no fields, unit (encoded as a 0-tuple).
513    ///
514    /// Less frequently: arbitrary ADT values.
515    ///
516    /// We eliminate this case in a micro-pass.
517    #[charon::opaque]
518    Adt(Option<VariantId>, Vec<ConstantExpr>),
519    #[charon::opaque]
520    Array(Vec<ConstantExpr>),
521    /// The value is a top-level constant/static.
522    ///
523    /// We eliminate this case in a micro-pass.
524    ///
525    /// Remark: constants can actually have generic parameters.
526    /// ```text
527    /// struct V<const N: usize, T> {
528    ///   x: [T; N],
529    /// }
530    ///
531    /// impl<const N: usize, T> V<N, T> {
532    ///   const LEN: usize = N; // This has generics <N, T>
533    /// }
534    ///
535    /// fn use_v<const N: usize, T>(v: V<N, T>) {
536    ///   let l = V::<N, T>::LEN; // We need to provided a substitution here
537    /// }
538    /// ```
539    #[charon::opaque]
540    Global(GlobalDeclRef),
541    ///
542    /// A trait constant.
543    ///
544    /// Ex.:
545    /// ```text
546    /// impl Foo for Bar {
547    ///   const C : usize = 32; // <-
548    /// }
549    /// ```
550    ///
551    /// Remark: trait constants can not be used in types, they are necessarily
552    /// values.
553    TraitConst(TraitRef, TraitItemName),
554    /// A shared reference to a constant value.
555    ///
556    /// We eliminate this case in a micro-pass.
557    #[charon::opaque]
558    Ref(Box<ConstantExpr>),
559    /// A pointer to a mutable static.
560    ///
561    /// We eliminate this case in a micro-pass.
562    #[charon::opaque]
563    Ptr(RefKind, Box<ConstantExpr>),
564    /// A const generic var
565    Var(ConstGenericDbVar),
566    /// Function pointer
567    FnPtr(FnPtr),
568    /// A pointer with no provenance (e.g. 0 for the null pointer)
569    ///
570    /// We eliminate this case in a micro-pass.
571    #[drive(skip)]
572    #[charon::opaque]
573    PtrNoProvenance(u128),
574    /// Raw memory value obtained from constant evaluation. Used when a more structured
575    /// representation isn't possible (e.g. for unions) or just isn't implemented yet.
576    #[drive(skip)]
577    RawMemory(Vec<u8>),
578    /// A constant expression that Charon still doesn't handle, along with the reason why.
579    #[drive(skip)]
580    Opaque(String),
581}
582
583#[derive(Debug, Hash, PartialEq, Eq, Clone, Serialize, Deserialize, Drive, DriveMut)]
584pub struct ConstantExpr {
585    pub kind: ConstantExprKind,
586    pub ty: Ty,
587}
588
589/// TODO: we could factor out [Rvalue] and function calls (for LLBC, not ULLBC).
590/// We can also factor out the unops, binops with the function calls.
591/// TODO: move the aggregate kind to operands
592/// TODO: we should prefix the type variants with "R" or "Rv", this would avoid collisions
593#[derive(
594    Debug, Clone, EnumToGetters, EnumAsGetters, EnumIsA, Serialize, Deserialize, Drive, DriveMut,
595)]
596pub enum Rvalue {
597    /// Lifts an operand as an rvalue.
598    Use(Operand),
599    /// Takes a reference to the given place.
600    /// The `Operand` refers to the init value of the metadata, it is `()` if no metadata
601    #[charon::rename("RvRef")]
602    Ref {
603        place: Place,
604        kind: BorrowKind,
605        ptr_metadata: Operand,
606    },
607    /// Takes a raw pointer with the given mutability to the given place. This is generated by
608    /// pointer casts like `&v as *const _` or raw borrow expressions like `&raw const v.`
609    /// Like `Ref`, the `Operand` refers to the init value of the metadata, it is `()` if no metadata.
610    RawPtr {
611        place: Place,
612        kind: RefKind,
613        ptr_metadata: Operand,
614    },
615    /// Binary operations (note that we merge "checked" and "unchecked" binops)
616    BinaryOp(BinOp, Operand, Operand),
617    /// Unary operation (e.g. not, neg)
618    UnaryOp(UnOp, Operand),
619    /// Nullary operation (e.g. `size_of`)
620    NullaryOp(NullOp, Ty),
621    /// Discriminant read. Reads the discriminant value of an enum. The place must have the type of
622    /// an enum.
623    ///
624    /// This case is filtered in [crate::transform::resugar::reconstruct_matches]
625    Discriminant(Place),
626    /// Creates an aggregate value, like a tuple, a struct or an enum:
627    /// ```text
628    /// l = List::Cons { value:x, tail:tl };
629    /// ```
630    /// Note that in some MIR passes (like optimized MIR), aggregate values are
631    /// decomposed, like below:
632    /// ```text
633    /// (l as List::Cons).value = x;
634    /// (l as List::Cons).tail = tl;
635    /// ```
636    /// Because we may want to plug our translation mechanism at various
637    /// places, we need to take both into accounts in the translation and in
638    /// our semantics. Aggregate value initialization is easy, you might want
639    /// to have a look at expansion of `Bottom` values for explanations about the
640    /// other case.
641    ///
642    /// Remark: in case of closures, the aggregated value groups the closure id
643    /// together with its state.
644    Aggregate(AggregateKind, Vec<Operand>),
645    /// Length of a place of type `[T]` or `[T; N]`. This applies to the place itself, not to a
646    /// pointer value. This is inserted by rustc in a single case: slice patterns.
647    /// ```text
648    /// fn slice_pattern_4(x: &[()]) {
649    ///     match x {
650    ///         [_named] => (),
651    ///         _ => (),
652    ///     }
653    /// }
654    /// ```
655    Len(Place, Ty, Option<ConstGeneric>),
656    /// `Repeat(x, n)` creates an array where `x` is copied `n` times.
657    ///
658    /// We translate this to a function call for LLBC.
659    Repeat(Operand, Ty, ConstGeneric),
660    /// Transmutes a `*mut u8` (obtained from `malloc`) into shallow-initialized `Box<T>`. This
661    /// only appears as part of lowering `Box::new()` in some cases. We reconstruct the original
662    /// `Box::new()` call, but sometimes may fail to do so, leaking the expression.
663    ShallowInitBox(Operand, Ty),
664}
665
666/// An aggregated ADT.
667///
668/// Note that ADTs are desaggregated at some point in MIR. For instance, if
669/// we have in Rust:
670/// ```ignore
671///   let ls = Cons(hd, tl);
672/// ```
673///
674/// In MIR we have (yes, the discriminant update happens *at the end* for some
675/// reason):
676/// ```text
677///   (ls as Cons).0 = move hd;
678///   (ls as Cons).1 = move tl;
679///   discriminant(ls) = 0; // assuming `Cons` is the variant of index 0
680/// ```
681///
682/// Rem.: in the Aeneas semantics, both cases are handled (in case of desaggregated
683/// initialization, `ls` is initialized to `⊥`, then this `⊥` is expanded to
684/// `Cons (⊥, ⊥)` upon the first assignment, at which point we can initialize
685/// the field 0, etc.).
686#[derive(Debug, Clone, VariantIndexArity, Serialize, Deserialize, Drive, DriveMut)]
687#[charon::variants_prefix("Aggregated")]
688pub enum AggregateKind {
689    /// A struct, enum or union aggregate. The `VariantId`, if present, indicates this is an enum
690    /// and the aggregate uses that variant. The `FieldId`, if present, indicates this is a union
691    /// and the aggregate writes into that field. Otherwise this is a struct.
692    Adt(TypeDeclRef, Option<VariantId>, Option<FieldId>),
693    /// We don't put this with the ADT cas because this is the only built-in type
694    /// with aggregates, and it is a primitive type. In particular, it makes
695    /// sense to treat it differently because it has a variable number of fields.
696    Array(Ty, ConstGeneric),
697    /// Construct a raw pointer from a pointer value, and its metadata (can be unit, if building
698    /// a thin pointer). The type is the type of the pointee.
699    /// We lower this to a builtin function call for LLBC in [crate::transform::simplify_output::ops_to_function_calls].
700    RawPtr(Ty, RefKind),
701}
charon_lib/ast/expressions.rs

charon_lib/ast/
expressions.rs
