| use crate::mir::interpret::LitToConstInput; |
| use crate::mir::ConstantKind; |
| use crate::ty::{self, InternalSubsts, ParamEnv, ParamEnvAnd, Ty, TyCtxt}; |
| use rustc_data_structures::intern::Interned; |
| use rustc_errors::ErrorGuaranteed; |
| use rustc_hir as hir; |
| use rustc_hir::def_id::{DefId, LocalDefId}; |
| use rustc_macros::HashStable; |
| use std::fmt; |
| |
| mod int; |
| mod kind; |
| mod valtree; |
| |
| pub use int::*; |
| pub use kind::*; |
| pub use valtree::*; |
| |
| /// Use this rather than `ConstS`, whenever possible. |
| #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, HashStable)] |
| #[rustc_pass_by_value] |
| pub struct Const<'tcx>(pub Interned<'tcx, ConstS<'tcx>>); |
| |
| impl<'tcx> fmt::Debug for Const<'tcx> { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| // This reflects what `Const` looked liked before `Interned` was |
| // introduced. We print it like this to avoid having to update expected |
| // output in a lot of tests. |
| write!(f, "Const {{ ty: {:?}, kind: {:?} }}", self.ty(), self.kind()) |
| } |
| } |
| |
| /// Typed constant value. |
| #[derive(PartialEq, Eq, PartialOrd, Ord, Hash, HashStable, TyEncodable, TyDecodable)] |
| pub struct ConstS<'tcx> { |
| pub ty: Ty<'tcx>, |
| pub kind: ConstKind<'tcx>, |
| } |
| |
| #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))] |
| static_assert_size!(ConstS<'_>, 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 |
| } |
| |
| /// Literals and const generic parameters are eagerly converted to a constant, everything else |
| /// becomes `Unevaluated`. |
| pub fn from_anon_const(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> Self { |
| Self::from_opt_const_arg_anon_const(tcx, ty::WithOptConstParam::unknown(def_id)) |
| } |
| |
| #[instrument(skip(tcx), level = "debug")] |
| pub fn from_opt_const_arg_anon_const( |
| tcx: TyCtxt<'tcx>, |
| def: ty::WithOptConstParam<LocalDefId>, |
| ) -> Self { |
| let body_id = match tcx.hir().get_by_def_id(def.did) { |
| hir::Node::AnonConst(ac) => ac.body, |
| _ => span_bug!( |
| tcx.def_span(def.did.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.def_id_for_type_of()); |
| |
| match Self::try_eval_lit_or_param(tcx, ty, expr) { |
| Some(v) => v, |
| None => tcx.mk_const(ty::ConstS { |
| kind: ty::ConstKind::Unevaluated(ty::UnevaluatedConst { |
| def: def.to_global(), |
| substs: InternalSubsts::identity_for_item(tcx, def.did.to_def_id()), |
| }), |
| ty, |
| }), |
| } |
| } |
| |
| #[instrument(skip(tcx), level = "debug")] |
| fn try_eval_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), |
| ); |
| } |
| } |
| } |
| |
| use hir::{def::DefKind::ConstParam, def::Res, ExprKind, Path, QPath}; |
| match expr.kind { |
| ExprKind::Path(QPath::Resolved(_, &Path { res: Res::Def(ConstParam, def_id), .. })) => { |
| // Find the name and index of the const parameter by indexing the generics of |
| // the parent item and construct a `ParamConst`. |
| let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local()); |
| let item_id = tcx.hir().get_parent_node(hir_id); |
| let item_def_id = tcx.hir().local_def_id(item_id); |
| let generics = tcx.generics_of(item_def_id.to_def_id()); |
| let index = generics.param_def_id_to_index[&def_id]; |
| let name = tcx.hir().name(hir_id); |
| Some(tcx.mk_const(ty::ConstS { |
| kind: ty::ConstKind::Param(ty::ParamConst::new(index, name)), |
| ty, |
| })) |
| } |
| _ => None, |
| } |
| } |
| |
| /// Interns the given value as a constant. |
| #[inline] |
| pub fn from_value(tcx: TyCtxt<'tcx>, val: ty::ValTree<'tcx>, ty: Ty<'tcx>) -> Self { |
| tcx.mk_const(ConstS { kind: ConstKind::Value(val), ty }) |
| } |
| |
| /// 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()), |
| } |
| } |
| |
| pub fn from_scalar_int(tcx: TyCtxt<'tcx>, i: ScalarInt, ty: Ty<'tcx>) -> Self { |
| let valtree = ty::ValTree::from_scalar_int(i); |
| Self::from_value(tcx, valtree, ty) |
| } |
| |
| #[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; |
| Self::from_scalar_int(tcx, 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 { |
| let valtree = ty::ValTree::zst(); |
| Self::from_value(tcx, valtree, 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_usize(tcx: TyCtxt<'tcx>, n: u64) -> Self { |
| Self::from_bits(tcx, n as u128, ParamEnv::empty().and(tcx.types.usize)) |
| } |
| |
| #[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>, |
| ty: Ty<'tcx>, |
| ) -> Option<u128> { |
| assert_eq!(self.ty(), ty); |
| let size = tcx.layout_of(param_env.with_reveal_all_normalized(tcx).and(ty)).ok()?.size; |
| // if `ty` does not depend on generic parameters, use an empty param_env |
| self.kind().eval(tcx, param_env).try_to_bits(size) |
| } |
| |
| #[inline] |
| pub fn try_eval_bool(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Option<bool> { |
| self.kind().eval(tcx, param_env).try_to_bool() |
| } |
| |
| #[inline] |
| pub fn try_eval_usize(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Option<u64> { |
| self.kind().eval(tcx, param_env).try_to_machine_usize(tcx) |
| } |
| |
| #[inline] |
| /// Tries to evaluate the constant if it is `Unevaluated`. If that doesn't succeed, return the |
| /// unevaluated constant. |
| pub fn eval(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Const<'tcx> { |
| if let Some(val) = self.kind().try_eval_for_typeck(tcx, param_env) { |
| match val { |
| Ok(val) => Const::from_value(tcx, val, self.ty()), |
| Err(ErrorGuaranteed { .. }) => tcx.const_error(self.ty()), |
| } |
| } else { |
| // Either the constant isn't evaluatable or ValTree creation failed. |
| self |
| } |
| } |
| |
| #[inline] |
| /// Tries to evaluate the constant if it is `Unevaluated` and creates a ConstValue if the |
| /// evaluation succeeds. If it doesn't succeed, returns the unevaluated constant. |
| pub fn eval_for_mir(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> ConstantKind<'tcx> { |
| if let Some(val) = self.kind().try_eval_for_mir(tcx, param_env) { |
| match val { |
| Ok(const_val) => ConstantKind::from_value(const_val, self.ty()), |
| Err(ErrorGuaranteed { .. }) => ConstantKind::Ty(tcx.const_error(self.ty())), |
| } |
| } else { |
| ConstantKind::Ty(self) |
| } |
| } |
| |
| #[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>, ty: Ty<'tcx>) -> u128 { |
| self.try_eval_bits(tcx, param_env, ty) |
| .unwrap_or_else(|| bug!("expected bits of {:#?}, got {:#?}", ty, self)) |
| } |
| |
| #[inline] |
| /// Panics if the value cannot be evaluated or doesn't contain a valid `usize`. |
| pub fn eval_usize(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> u64 { |
| self.try_eval_usize(tcx, param_env) |
| .unwrap_or_else(|| bug!("expected usize, got {:#?}", self)) |
| } |
| |
| pub fn is_ct_infer(self) -> bool { |
| matches!(self.kind(), ty::ConstKind::Infer(_)) |
| } |
| } |
| |
| pub fn const_param_default<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> Const<'tcx> { |
| let default_def_id = match tcx.hir().get_by_def_id(def_id.expect_local()) { |
| hir::Node::GenericParam(hir::GenericParam { |
| kind: hir::GenericParamKind::Const { ty: _, default: Some(ac) }, |
| .. |
| }) => tcx.hir().local_def_id(ac.hir_id), |
| _ => span_bug!( |
| tcx.def_span(def_id), |
| "`const_param_default` expected a generic parameter with a constant" |
| ), |
| }; |
| Const::from_anon_const(tcx, default_def_id) |
| } |
