| use crate::middle::resolve_bound_vars as rbv; |
| use crate::mir::interpret::{AllocId, ErrorHandled, LitToConstInput, Scalar}; |
| use crate::ty::{self, GenericArgs, ParamEnv, ParamEnvAnd, Ty, TyCtxt, TypeVisitableExt}; |
| use rustc_data_structures::intern::Interned; |
| use rustc_error_messages::MultiSpan; |
| use rustc_hir as hir; |
| use rustc_hir::def::{DefKind, Res}; |
| use rustc_hir::def_id::LocalDefId; |
| use rustc_macros::HashStable; |
| |
| mod int; |
| mod kind; |
| mod valtree; |
| |
| pub use int::*; |
| pub use kind::*; |
| use rustc_span::Span; |
| use rustc_span::DUMMY_SP; |
| pub use valtree::*; |
| |
| use super::sty::ConstKind; |
| |
| /// Use this rather than `ConstData`, whenever possible. |
| #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, HashStable)] |
| #[rustc_pass_by_value] |
| pub struct Const<'tcx>(pub(super) Interned<'tcx, ConstData<'tcx>>); |
| |
| /// Typed constant value. |
| #[derive(PartialEq, Eq, PartialOrd, Ord, Hash, HashStable, TyEncodable, TyDecodable)] |
| pub struct ConstData<'tcx> { |
| pub ty: Ty<'tcx>, |
| pub kind: ConstKind<'tcx>, |
| } |
| |
| #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))] |
| static_assert_size!(ConstData<'_>, 40); |
| |
| impl<'tcx> Const<'tcx> { |
| #[inline] |
| pub fn ty(self) -> Ty<'tcx> { |
| self.0.ty |
| } |
| |
| #[inline] |
| pub fn kind(self) -> ConstKind<'tcx> { |
| self.0.kind.clone() |
| } |
| |
| #[inline] |
| pub fn new(tcx: TyCtxt<'tcx>, kind: ty::ConstKind<'tcx>, ty: Ty<'tcx>) -> Const<'tcx> { |
| tcx.mk_ct_from_kind(kind, ty) |
| } |
| |
| #[inline] |
| pub fn new_param(tcx: TyCtxt<'tcx>, param: ty::ParamConst, ty: Ty<'tcx>) -> Const<'tcx> { |
| Const::new(tcx, ty::ConstKind::Param(param), ty) |
| } |
| |
| #[inline] |
| pub fn new_var(tcx: TyCtxt<'tcx>, infer: ty::ConstVid, ty: Ty<'tcx>) -> Const<'tcx> { |
| Const::new(tcx, ty::ConstKind::Infer(ty::InferConst::Var(infer)), ty) |
| } |
| |
| #[inline] |
| pub fn new_fresh(tcx: TyCtxt<'tcx>, fresh: u32, ty: Ty<'tcx>) -> Const<'tcx> { |
| Const::new(tcx, ty::ConstKind::Infer(ty::InferConst::Fresh(fresh)), ty) |
| } |
| |
| #[inline] |
| pub fn new_infer(tcx: TyCtxt<'tcx>, infer: ty::InferConst, ty: Ty<'tcx>) -> Const<'tcx> { |
| Const::new(tcx, ty::ConstKind::Infer(infer), ty) |
| } |
| |
| #[inline] |
| pub fn new_bound( |
| tcx: TyCtxt<'tcx>, |
| debruijn: ty::DebruijnIndex, |
| var: ty::BoundVar, |
| ty: Ty<'tcx>, |
| ) -> Const<'tcx> { |
| Const::new(tcx, ty::ConstKind::Bound(debruijn, var), ty) |
| } |
| |
| #[inline] |
| pub fn new_placeholder( |
| tcx: TyCtxt<'tcx>, |
| placeholder: ty::PlaceholderConst, |
| ty: Ty<'tcx>, |
| ) -> Const<'tcx> { |
| Const::new(tcx, ty::ConstKind::Placeholder(placeholder), ty) |
| } |
| |
| #[inline] |
| pub fn new_unevaluated( |
| tcx: TyCtxt<'tcx>, |
| uv: ty::UnevaluatedConst<'tcx>, |
| ty: Ty<'tcx>, |
| ) -> Const<'tcx> { |
| Const::new(tcx, ty::ConstKind::Unevaluated(uv), ty) |
| } |
| |
| #[inline] |
| pub fn new_value(tcx: TyCtxt<'tcx>, val: ty::ValTree<'tcx>, ty: Ty<'tcx>) -> Const<'tcx> { |
| Const::new(tcx, ty::ConstKind::Value(val), ty) |
| } |
| |
| #[inline] |
| pub fn new_expr(tcx: TyCtxt<'tcx>, expr: ty::Expr<'tcx>, ty: Ty<'tcx>) -> Const<'tcx> { |
| Const::new(tcx, ty::ConstKind::Expr(expr), ty) |
| } |
| |
| #[inline] |
| pub fn new_error(tcx: TyCtxt<'tcx>, e: ty::ErrorGuaranteed, ty: Ty<'tcx>) -> Const<'tcx> { |
| Const::new(tcx, ty::ConstKind::Error(e), ty) |
| } |
| |
| /// Like [Ty::new_error] but for constants. |
| #[track_caller] |
| pub fn new_misc_error(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Const<'tcx> { |
| Const::new_error_with_message( |
| tcx, |
| ty, |
| DUMMY_SP, |
| "ty::ConstKind::Error constructed but no error reported", |
| ) |
| } |
| |
| /// Like [Ty::new_error_with_message] but for constants. |
| #[track_caller] |
| pub fn new_error_with_message<S: Into<MultiSpan>>( |
| tcx: TyCtxt<'tcx>, |
| ty: Ty<'tcx>, |
| span: S, |
| msg: &'static str, |
| ) -> Const<'tcx> { |
| let reported = tcx.sess.delay_span_bug(span, msg); |
| Const::new_error(tcx, reported, ty) |
| } |
| |
| /// Literals and const generic parameters are eagerly converted to a constant, everything else |
| /// becomes `Unevaluated`. |
| #[instrument(skip(tcx), level = "debug")] |
| pub fn from_anon_const(tcx: TyCtxt<'tcx>, def: LocalDefId) -> Self { |
| let body_id = match tcx.hir().get_by_def_id(def) { |
| hir::Node::AnonConst(ac) => ac.body, |
| _ => span_bug!( |
| tcx.def_span(def.to_def_id()), |
| "from_anon_const can only process anonymous constants" |
| ), |
| }; |
| |
| let expr = &tcx.hir().body(body_id).value; |
| debug!(?expr); |
| |
| let ty = tcx.type_of(def).no_bound_vars().expect("const parameter types cannot be generic"); |
| |
| match Self::try_from_lit_or_param(tcx, ty, expr) { |
| Some(v) => v, |
| None => ty::Const::new_unevaluated( |
| tcx, |
| ty::UnevaluatedConst { |
| def: def.to_def_id(), |
| args: GenericArgs::identity_for_item(tcx, def.to_def_id()), |
| }, |
| ty, |
| ), |
| } |
| } |
| |
| #[instrument(skip(tcx), level = "debug")] |
| fn try_from_lit_or_param( |
| tcx: TyCtxt<'tcx>, |
| ty: Ty<'tcx>, |
| expr: &'tcx hir::Expr<'tcx>, |
| ) -> Option<Self> { |
| // Unwrap a block, so that e.g. `{ P }` is recognised as a parameter. Const arguments |
| // currently have to be wrapped in curly brackets, so it's necessary to special-case. |
| let expr = match &expr.kind { |
| hir::ExprKind::Block(block, _) if block.stmts.is_empty() && block.expr.is_some() => { |
| block.expr.as_ref().unwrap() |
| } |
| _ => expr, |
| }; |
| |
| let lit_input = match expr.kind { |
| hir::ExprKind::Lit(ref lit) => Some(LitToConstInput { lit: &lit.node, ty, neg: false }), |
| hir::ExprKind::Unary(hir::UnOp::Neg, ref expr) => match expr.kind { |
| hir::ExprKind::Lit(ref lit) => { |
| Some(LitToConstInput { lit: &lit.node, ty, neg: true }) |
| } |
| _ => None, |
| }, |
| _ => None, |
| }; |
| |
| if let Some(lit_input) = lit_input { |
| // If an error occurred, ignore that it's a literal and leave reporting the error up to |
| // mir. |
| match tcx.at(expr.span).lit_to_const(lit_input) { |
| Ok(c) => return Some(c), |
| Err(e) => { |
| tcx.sess.delay_span_bug( |
| expr.span, |
| format!("Const::from_anon_const: couldn't lit_to_const {e:?}"), |
| ); |
| } |
| } |
| } |
| |
| match expr.kind { |
| hir::ExprKind::Path(hir::QPath::Resolved( |
| _, |
| &hir::Path { res: Res::Def(DefKind::ConstParam, def_id), .. }, |
| )) => { |
| // Use the type from the param's definition, since we can resolve it, |
| // not the expected parameter type from WithOptConstParam. |
| let param_ty = tcx.type_of(def_id).instantiate_identity(); |
| match tcx.named_bound_var(expr.hir_id) { |
| Some(rbv::ResolvedArg::EarlyBound(_)) => { |
| // Find the name and index of the const parameter by indexing the generics of |
| // the parent item and construct a `ParamConst`. |
| let item_def_id = tcx.parent(def_id); |
| let generics = tcx.generics_of(item_def_id); |
| let index = generics.param_def_id_to_index[&def_id]; |
| let name = tcx.item_name(def_id); |
| Some(ty::Const::new_param(tcx, ty::ParamConst::new(index, name), param_ty)) |
| } |
| Some(rbv::ResolvedArg::LateBound(debruijn, index, _)) => { |
| Some(ty::Const::new_bound( |
| tcx, |
| debruijn, |
| ty::BoundVar::from_u32(index), |
| param_ty, |
| )) |
| } |
| Some(rbv::ResolvedArg::Error(guar)) => { |
| Some(ty::Const::new_error(tcx, guar, param_ty)) |
| } |
| arg => bug!("unexpected bound var resolution for {:?}: {arg:?}", expr.hir_id), |
| } |
| } |
| _ => None, |
| } |
| } |
| |
| #[inline] |
| /// Creates a constant with the given integer value and interns it. |
| pub fn from_bits(tcx: TyCtxt<'tcx>, bits: u128, ty: ParamEnvAnd<'tcx, Ty<'tcx>>) -> Self { |
| let size = tcx |
| .layout_of(ty) |
| .unwrap_or_else(|e| panic!("could not compute layout for {ty:?}: {e:?}")) |
| .size; |
| ty::Const::new_value( |
| tcx, |
| ty::ValTree::from_scalar_int(ScalarInt::try_from_uint(bits, size).unwrap()), |
| ty.value, |
| ) |
| } |
| |
| #[inline] |
| /// Creates an interned zst constant. |
| pub fn zero_sized(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Self { |
| ty::Const::new_value(tcx, ty::ValTree::zst(), ty) |
| } |
| |
| #[inline] |
| /// Creates an interned bool constant. |
| pub fn from_bool(tcx: TyCtxt<'tcx>, v: bool) -> Self { |
| Self::from_bits(tcx, v as u128, ParamEnv::empty().and(tcx.types.bool)) |
| } |
| |
| #[inline] |
| /// Creates an interned usize constant. |
| pub fn from_target_usize(tcx: TyCtxt<'tcx>, n: u64) -> Self { |
| Self::from_bits(tcx, n as u128, ParamEnv::empty().and(tcx.types.usize)) |
| } |
| |
| /// Returns the evaluated constant |
| #[inline] |
| pub fn eval( |
| self, |
| tcx: TyCtxt<'tcx>, |
| param_env: ParamEnv<'tcx>, |
| span: Option<Span>, |
| ) -> Result<ValTree<'tcx>, ErrorHandled> { |
| assert!(!self.has_escaping_bound_vars(), "escaping vars in {self:?}"); |
| match self.kind() { |
| ConstKind::Unevaluated(unevaluated) => { |
| // FIXME(eddyb) maybe the `const_eval_*` methods should take |
| // `ty::ParamEnvAnd` instead of having them separate. |
| let (param_env, unevaluated) = unevaluated.prepare_for_eval(tcx, param_env); |
| // try to resolve e.g. associated constants to their definition on an impl, and then |
| // evaluate the const. |
| let c = tcx.const_eval_resolve_for_typeck(param_env, unevaluated, span)?; |
| Ok(c.expect("`ty::Const::eval` called on a non-valtree-compatible type")) |
| } |
| ConstKind::Value(val) => Ok(val), |
| ConstKind::Error(g) => Err(g.into()), |
| ConstKind::Param(_) |
| | ConstKind::Infer(_) |
| | ConstKind::Bound(_, _) |
| | ConstKind::Placeholder(_) |
| | ConstKind::Expr(_) => Err(ErrorHandled::TooGeneric(span.unwrap_or(DUMMY_SP))), |
| } |
| } |
| |
| /// Normalizes the constant to a value or an error if possible. |
| #[inline] |
| pub fn normalize(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Self { |
| match self.eval(tcx, param_env, None) { |
| Ok(val) => Self::new_value(tcx, val, self.ty()), |
| Err(ErrorHandled::Reported(r, _span)) => Self::new_error(tcx, r.into(), self.ty()), |
| Err(ErrorHandled::TooGeneric(_span)) => self, |
| } |
| } |
| |
| #[inline] |
| pub fn try_eval_scalar( |
| self, |
| tcx: TyCtxt<'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| ) -> Option<Scalar> { |
| self.eval(tcx, param_env, None).ok()?.try_to_scalar() |
| } |
| |
| #[inline] |
| /// Attempts to evaluate the given constant to bits. Can fail to evaluate in the presence of |
| /// generics (or erroneous code) or if the value can't be represented as bits (e.g. because it |
| /// contains const generic parameters or pointers). |
| pub fn try_eval_scalar_int( |
| self, |
| tcx: TyCtxt<'tcx>, |
| param_env: ParamEnv<'tcx>, |
| ) -> Option<ScalarInt> { |
| self.try_eval_scalar(tcx, param_env)?.try_to_int().ok() |
| } |
| |
| #[inline] |
| /// Attempts to evaluate the given constant to bits. Can fail to evaluate in the presence of |
| /// generics (or erroneous code) or if the value can't be represented as bits (e.g. because it |
| /// contains const generic parameters or pointers). |
| pub fn try_eval_bits(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Option<u128> { |
| let int = self.try_eval_scalar_int(tcx, param_env)?; |
| let size = |
| tcx.layout_of(param_env.with_reveal_all_normalized(tcx).and(self.ty())).ok()?.size; |
| // if `ty` does not depend on generic parameters, use an empty param_env |
| int.to_bits(size).ok() |
| } |
| |
| #[inline] |
| /// Panics if the value cannot be evaluated or doesn't contain a valid integer of the given type. |
| pub fn eval_bits(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> u128 { |
| self.try_eval_bits(tcx, param_env) |
| .unwrap_or_else(|| bug!("expected bits of {:#?}, got {:#?}", self.ty(), self)) |
| } |
| |
| #[inline] |
| pub fn try_eval_target_usize( |
| self, |
| tcx: TyCtxt<'tcx>, |
| param_env: ParamEnv<'tcx>, |
| ) -> Option<u64> { |
| self.try_eval_scalar_int(tcx, param_env)?.try_to_target_usize(tcx).ok() |
| } |
| |
| #[inline] |
| pub fn try_eval_bool(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Option<bool> { |
| self.try_eval_scalar_int(tcx, param_env)?.try_into().ok() |
| } |
| |
| #[inline] |
| /// Panics if the value cannot be evaluated or doesn't contain a valid `usize`. |
| pub fn eval_target_usize(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> u64 { |
| self.try_eval_target_usize(tcx, param_env) |
| .unwrap_or_else(|| bug!("expected usize, got {:#?}", self)) |
| } |
| |
| /// Panics if self.kind != ty::ConstKind::Value |
| pub fn to_valtree(self) -> ty::ValTree<'tcx> { |
| match self.kind() { |
| ty::ConstKind::Value(valtree) => valtree, |
| _ => bug!("expected ConstKind::Value, got {:?}", self.kind()), |
| } |
| } |
| |
| /// Attempts to convert to a `ValTree` |
| pub fn try_to_valtree(self) -> Option<ty::ValTree<'tcx>> { |
| match self.kind() { |
| ty::ConstKind::Value(valtree) => Some(valtree), |
| _ => None, |
| } |
| } |
| |
| #[inline] |
| pub fn try_to_scalar(self) -> Option<Scalar<AllocId>> { |
| self.try_to_valtree()?.try_to_scalar() |
| } |
| |
| #[inline] |
| pub fn try_to_target_usize(self, tcx: TyCtxt<'tcx>) -> Option<u64> { |
| self.try_to_valtree()?.try_to_target_usize(tcx) |
| } |
| |
| pub fn is_ct_infer(self) -> bool { |
| matches!(self.kind(), ty::ConstKind::Infer(_)) |
| } |
| } |
| |
| pub fn const_param_default(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<Const<'_>> { |
| let default_def_id = match tcx.hir().get_by_def_id(def_id) { |
| hir::Node::GenericParam(hir::GenericParam { |
| kind: hir::GenericParamKind::Const { default: Some(ac), .. }, |
| .. |
| }) => ac.def_id, |
| _ => span_bug!( |
| tcx.def_span(def_id), |
| "`const_param_default` expected a generic parameter with a constant" |
| ), |
| }; |
| ty::EarlyBinder::bind(Const::from_anon_const(tcx, default_def_id)) |
| } |