| use crate::mir::interpret::ConstValue; |
| use crate::mir::interpret::{LitToConstInput, Scalar}; |
| use crate::ty::subst::InternalSubsts; |
| use crate::ty::{self, Ty, TyCtxt}; |
| use crate::ty::{ParamEnv, ParamEnvAnd}; |
| use rustc_errors::ErrorReported; |
| use rustc_hir as hir; |
| use rustc_hir::def_id::LocalDefId; |
| use rustc_macros::HashStable; |
| |
| mod int; |
| mod kind; |
| mod normalize; |
| |
| pub use int::*; |
| pub use kind::*; |
| |
| /// Typed constant value. |
| #[derive(Copy, Clone, Debug, Hash, TyEncodable, TyDecodable, Eq, PartialEq, Ord, PartialOrd)] |
| #[derive(HashStable)] |
| pub struct Const<'tcx> { |
| pub ty: Ty<'tcx>, |
| |
| pub val: ConstKind<'tcx>, |
| } |
| |
| #[cfg(target_arch = "x86_64")] |
| static_assert_size!(Const<'_>, 48); |
| |
| impl<'tcx> Const<'tcx> { |
| /// 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) -> &'tcx Self { |
| Self::from_opt_const_arg_anon_const(tcx, ty::WithOptConstParam::unknown(def_id)) |
| } |
| |
| pub fn from_opt_const_arg_anon_const( |
| tcx: TyCtxt<'tcx>, |
| def: ty::WithOptConstParam<LocalDefId>, |
| ) -> &'tcx Self { |
| debug!("Const::from_anon_const(def={:?})", def); |
| |
| let hir_id = tcx.hir().local_def_id_to_hir_id(def.did); |
| |
| let body_id = match tcx.hir().get(hir_id) { |
| 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; |
| |
| let ty = tcx.type_of(def.def_id_for_type_of()); |
| |
| let lit_input = match expr.kind { |
| hir::ExprKind::Lit(ref lit) => Some(LitToConstInput { lit: &lit.node, ty, neg: false }), |
| hir::ExprKind::Unary(hir::UnOp::UnNeg, 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. |
| if let Ok(c) = tcx.at(expr.span).lit_to_const(lit_input) { |
| return c; |
| } else { |
| tcx.sess.delay_span_bug(expr.span, "Const::from_anon_const: couldn't lit_to_const"); |
| } |
| } |
| |
| // 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, |
| }; |
| |
| use hir::{def::DefKind::ConstParam, def::Res, ExprKind, Path, QPath}; |
| let val = 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[&tcx.hir().local_def_id(hir_id).to_def_id()]; |
| let name = tcx.hir().name(hir_id); |
| ty::ConstKind::Param(ty::ParamConst::new(index, name)) |
| } |
| _ => ty::ConstKind::Unevaluated( |
| def.to_global(), |
| InternalSubsts::identity_for_item(tcx, def.did.to_def_id()), |
| None, |
| ), |
| }; |
| |
| tcx.mk_const(ty::Const { val, ty }) |
| } |
| |
| #[inline] |
| /// Interns the given value as a constant. |
| pub fn from_value(tcx: TyCtxt<'tcx>, val: ConstValue<'tcx>, ty: Ty<'tcx>) -> &'tcx Self { |
| tcx.mk_const(Self { val: ConstKind::Value(val), ty }) |
| } |
| |
| #[inline] |
| /// Interns the given scalar as a constant. |
| pub fn from_scalar(tcx: TyCtxt<'tcx>, val: Scalar, ty: Ty<'tcx>) -> &'tcx Self { |
| Self::from_value(tcx, ConstValue::Scalar(val), 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>>) -> &'tcx Self { |
| let size = tcx |
| .layout_of(ty) |
| .unwrap_or_else(|e| panic!("could not compute layout for {:?}: {:?}", ty, e)) |
| .size; |
| Self::from_scalar(tcx, Scalar::from_uint(bits, size), ty.value) |
| } |
| |
| #[inline] |
| /// Creates an interned zst constant. |
| pub fn zero_sized(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> &'tcx Self { |
| Self::from_scalar(tcx, Scalar::ZST, ty) |
| } |
| |
| #[inline] |
| /// Creates an interned bool constant. |
| pub fn from_bool(tcx: TyCtxt<'tcx>, v: bool) -> &'tcx 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) -> &'tcx 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.val.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.val.eval(tcx, param_env).try_to_bool() |
| } |
| |
| #[inline] |
| pub fn try_eval_usize(&self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Option<u64> { |
| self.val.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.val.try_eval(tcx, param_env) { |
| match val { |
| Ok(val) => Const::from_value(tcx, val, self.ty), |
| Err(ErrorReported) => tcx.const_error(self.ty), |
| } |
| } else { |
| 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)) |
| } |
| } |