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

charon_lib/ast/
expressions.rs
