Enum RawConstantExpr

pub enum RawConstantExpr {
    Literal(Literal),
    Adt(Option<VariantId>, Vec<ConstantExpr>),
    Global(GlobalDeclRef),
    TraitConst(TraitRef, TraitItemName),
    Ref(Box<ConstantExpr>),
    MutPtr(Box<ConstantExpr>),
    Var(ConstGenericVarId),
    FnPtr(FnPtr),
}

A constant expression.

Only the Literal and Var cases are left in the final LLBC.

The other cases come from a straight translation from the MIR:

[Adt] case: It is a bit annoying, but rustc treats some ADT and tuple instances as constants when generating MIR:

• an enumeration with one variant and no fields is a constant.
• a structure with no field is a constant.
• sometimes, Rust stores the initialization of an ADT as a constant (if all the fields are constant) rather than as an aggregated value We later desugar those to regular ADTs, see [regularize_constant_adts.rs].

[Global] case: access to a global variable. We later desugar it to a separate statement.

[Ref] case: reference to a constant value. We later desugar it to a separate statement.

FnPtr case: a function pointer (to a top-level function).

Remark: MIR seems to forbid more complex expressions like paths. For instance, reading the constant a.b is translated to { _1 = const a; _2 = (_1.0) }.

Variants

Literal(Literal)

Adt(Option<VariantId>, Vec<ConstantExpr>)

In most situations: Enumeration with one variant with no fields, structure with no fields, unit (encoded as a 0-tuple).

Less frequently: arbitrary ADT values.

We eliminate this case in a micro-pass.

Global(GlobalDeclRef)

The value is a top-level constant/static.

We eliminate this case in a micro-pass.

Remark: constants can actually have generic parameters.

struct V<const N: usize, T> {
  x: [T; N],
}

impl<const N: usize, T> V<N, T> {
  const LEN: usize = N; // This has generics <N, T>
}

fn use_v<const N: usize, T>(v: V<N, T>) {
  let l = V::<N, T>::LEN; // We need to provided a substitution here
}

TraitConst(TraitRef, TraitItemName)

A trait constant.

Ex.:

impl Foo for Bar {
  const C : usize = 32; // <-
}

Remark: trait constants can not be used in types, they are necessarily values.

Ref(Box<ConstantExpr>)

A shared reference to a constant value.

We eliminate this case in a micro-pass.

MutPtr(Box<ConstantExpr>)

A mutable pointer to a mutable static.

We eliminate this case in a micro-pass.

Var(ConstGenericVarId)

A const generic var

FnPtr(FnPtr)

Function pointer

Implementations

impl RawConstantExpr

pub fn variant_name(&self) -> &'static str

impl RawConstantExpr

pub fn is_literal(&self) -> bool

pub fn is_adt(&self) -> bool

pub fn is_global(&self) -> bool

pub fn is_trait_const(&self) -> bool

pub fn is_ref(&self) -> bool

pub fn is_mut_ptr(&self) -> bool

pub fn is_var(&self) -> bool

pub fn is_fn_ptr(&self) -> bool

impl RawConstantExpr

pub fn as_literal(&self) -> Option<&Literal>

pub fn as_adt(&self) -> Option<(&Option<VariantId>, &Vec<ConstantExpr>)>

pub fn as_global(&self) -> Option<&GlobalDeclRef>

pub fn as_trait_const(&self) -> Option<(&TraitRef, &TraitItemName)>

pub fn as_ref(&self) -> Option<&Box<ConstantExpr>>

pub fn as_mut_ptr(&self) -> Option<&Box<ConstantExpr>>

pub fn as_var(&self) -> Option<&ConstGenericVarId>

pub fn as_fn_ptr(&self) -> Option<&FnPtr>

impl RawConstantExpr

pub fn as_literal_mut(&mut self) -> Option<&mut Literal>

pub fn as_adt_mut( &mut self, ) -> Option<(&mut Option<VariantId>, &mut Vec<ConstantExpr>)>

pub fn as_global_mut(&mut self) -> Option<&mut GlobalDeclRef>

pub fn as_trait_const_mut( &mut self, ) -> Option<(&mut TraitRef, &mut TraitItemName)>

pub fn as_ref_mut(&mut self) -> Option<&mut Box<ConstantExpr>>

pub fn as_mut_ptr_mut(&mut self) -> Option<&mut Box<ConstantExpr>>

pub fn as_var_mut(&mut self) -> Option<&mut ConstGenericVarId>

pub fn as_fn_ptr_mut(&mut self) -> Option<&mut FnPtr>

Trait Implementations

impl Clone for RawConstantExpr

fn clone(&self) -> RawConstantExpr

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for RawConstantExpr

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for RawConstantExpr

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Drive for RawConstantExpr

fn drive<V: Visitor>(&self, visitor: &mut V)

impl DriveMut for RawConstantExpr

fn drive_mut<V: VisitorMut>(&mut self, visitor: &mut V)

impl<C: AstFormatter> FmtWithCtx<C> for RawConstantExpr

fn fmt_with_ctx(&self, ctx: &C) -> String

fn fmt_with_ctx_and_indent(&self, _tab: &str, _ctx: &C) -> String

fn with_ctx<'a>(&'a self, ctx: &'a C) -> impl Display + 'a

Returns a struct that implements Display. This allows the following:

impl PartialEq for RawConstantExpr

fn eq(&self, other: &RawConstantExpr) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Serialize for RawConstantExpr

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl Eq for RawConstantExpr

impl StructuralPartialEq for RawConstantExpr