use crate::mir::interpret::LitToConstInput; use crate::mir::ConstantKind; use crate::ty::{ self, InlineConstSubsts, InlineConstSubstsParts, InternalSubsts, ParamEnv, ParamEnvAnd, Ty, TyCtxt, TypeVisitable, }; 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, ) -> 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::Unevaluated { def: def.to_global(), substs: InternalSubsts::identity_for_item(tcx, def.did.to_def_id()), promoted: (), }), ty, }), } } #[instrument(skip(tcx), level = "debug")] fn try_eval_lit_or_param( tcx: TyCtxt<'tcx>, ty: Ty<'tcx>, expr: &'tcx hir::Expr<'tcx>, ) -> Option { // 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, } } pub fn from_inline_const(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> Self { debug!("Const::from_inline_const(def_id={:?})", def_id); let hir_id = tcx.hir().local_def_id_to_hir_id(def_id); let body_id = match tcx.hir().get(hir_id) { hir::Node::AnonConst(ac) => ac.body, _ => span_bug!( tcx.def_span(def_id.to_def_id()), "from_inline_const can only process anonymous constants" ), }; let expr = &tcx.hir().body(body_id).value; let ty = tcx.typeck(def_id).node_type(hir_id); let ret = match Self::try_eval_lit_or_param(tcx, ty, expr) { Some(v) => v, None => { let typeck_root_def_id = tcx.typeck_root_def_id(def_id.to_def_id()); let parent_substs = tcx.erase_regions(InternalSubsts::identity_for_item(tcx, typeck_root_def_id)); let substs = InlineConstSubsts::new(tcx, InlineConstSubstsParts { parent_substs, ty }) .substs; tcx.mk_const(ty::ConstS { kind: ty::ConstKind::Unevaluated(ty::Unevaluated { def: ty::WithOptConstParam::unknown(def_id).to_global(), substs, promoted: (), }), ty, }) } }; debug_assert!(!ret.has_free_regions()); ret } /// 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 { 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 { self.kind().eval(tcx, param_env).try_to_bool() } #[inline] pub fn try_eval_usize(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Option { 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 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) }