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Diffstat (limited to 'compiler/rustc_middle/src/ty/consts.rs')
| -rw-r--r-- | compiler/rustc_middle/src/ty/consts.rs | 326 |
1 files changed, 326 insertions, 0 deletions
diff --git a/compiler/rustc_middle/src/ty/consts.rs b/compiler/rustc_middle/src/ty/consts.rs new file mode 100644 index 000000000..f8792edc0 --- /dev/null +++ b/compiler/rustc_middle/src/ty/consts.rs @@ -0,0 +1,326 @@ +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<'_>, 48); + +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 { + debug!("Const::from_anon_const(def={:?})", def); + + 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: None, + }), + 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, + } + } + + 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: None, + }), + 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<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 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) +} |