1 //! This module contains the functionality to convert from the wacky tcx data
2 //! structures into the THIR. The `builder` is generally ignorant of the tcx,
3 //! etc., and instead goes through the `Cx` for most of its work.
5 use crate::thir::util::UserAnnotatedTyHelpers;
10 use rustc_hir::def_id::{DefId, LocalDefId};
12 use rustc_index::vec::Idx;
13 use rustc_infer::infer::InferCtxt;
14 use rustc_middle::middle::region;
15 use rustc_middle::mir::interpret::{LitToConstError, LitToConstInput};
16 use rustc_middle::ty::subst::Subst;
17 use rustc_middle::ty::subst::{GenericArg, InternalSubsts};
18 use rustc_middle::ty::{self, Ty, TyCtxt};
19 use rustc_span::symbol::{sym, Symbol};
20 use rustc_target::abi::VariantIdx;
21 use rustc_trait_selection::infer::InferCtxtExt;
24 crate struct Cx<'a, 'tcx> {
26 infcx: &'a InferCtxt<'a, 'tcx>,
28 crate root_lint_level: hir::HirId,
29 crate param_env: ty::ParamEnv<'tcx>,
31 /// Identity `InternalSubsts` for use with const-evaluation.
32 crate identity_substs: &'tcx InternalSubsts<'tcx>,
34 crate region_scope_tree: &'tcx region::ScopeTree,
35 crate typeck_results: &'a ty::TypeckResults<'tcx>,
37 /// This is `Constness::Const` if we are compiling a `static`,
38 /// `const`, or the body of a `const fn`.
39 constness: hir::Constness,
41 /// The `DefId` of the owner of this body.
44 /// What kind of body is being compiled.
45 crate body_owner_kind: hir::BodyOwnerKind,
47 /// Whether this constant/function needs overflow checks.
51 impl<'a, 'tcx> Cx<'a, 'tcx> {
53 infcx: &'a InferCtxt<'a, 'tcx>,
54 def: ty::WithOptConstParam<LocalDefId>,
58 let typeck_results = tcx.typeck_opt_const_arg(def);
59 let body_owner_kind = tcx.hir().body_owner_kind(src_id);
61 let constness = match body_owner_kind {
62 hir::BodyOwnerKind::Const | hir::BodyOwnerKind::Static(_) => hir::Constness::Const,
63 hir::BodyOwnerKind::Closure | hir::BodyOwnerKind::Fn => hir::Constness::NotConst,
66 let attrs = tcx.hir().attrs(src_id);
68 // Some functions always have overflow checks enabled,
69 // however, they may not get codegen'd, depending on
70 // the settings for the crate they are codegened in.
71 let mut check_overflow = tcx.sess.contains_name(attrs, sym::rustc_inherit_overflow_checks);
73 // Respect -C overflow-checks.
74 check_overflow |= tcx.sess.overflow_checks();
76 // Constants always need overflow checks.
77 check_overflow |= constness == hir::Constness::Const;
82 root_lint_level: src_id,
83 param_env: tcx.param_env(def.did),
84 identity_substs: InternalSubsts::identity_for_item(tcx, def.did.to_def_id()),
85 region_scope_tree: tcx.region_scope_tree(def.did),
88 body_owner: def.did.to_def_id(),
95 impl<'a, 'tcx> Cx<'a, 'tcx> {
96 /// Normalizes `ast` into the appropriate "mirror" type.
97 crate fn mirror<M: Mirror<'tcx>>(&mut self, ast: M) -> M::Output {
101 crate fn usize_ty(&mut self) -> Ty<'tcx> {
105 crate fn usize_literal(&mut self, value: u64) -> &'tcx ty::Const<'tcx> {
106 ty::Const::from_usize(self.tcx, value)
109 crate fn bool_ty(&mut self) -> Ty<'tcx> {
113 crate fn unit_ty(&mut self) -> Ty<'tcx> {
117 crate fn true_literal(&mut self) -> &'tcx ty::Const<'tcx> {
118 ty::Const::from_bool(self.tcx, true)
121 crate fn false_literal(&mut self) -> &'tcx ty::Const<'tcx> {
122 ty::Const::from_bool(self.tcx, false)
125 crate fn const_eval_literal(
127 lit: &'tcx ast::LitKind,
131 ) -> &'tcx ty::Const<'tcx> {
132 trace!("const_eval_literal: {:#?}, {:?}, {:?}, {:?}", lit, ty, sp, neg);
134 match self.tcx.at(sp).lit_to_const(LitToConstInput { lit, ty, neg }) {
136 Err(LitToConstError::UnparseableFloat) => {
137 // FIXME(#31407) this is only necessary because float parsing is buggy
138 self.tcx.sess.span_err(sp, "could not evaluate float literal (see issue #31407)");
139 // create a dummy value and continue compiling
140 Const::from_bits(self.tcx, 0, self.param_env.and(ty))
142 Err(LitToConstError::Reported) => {
143 // create a dummy value and continue compiling
144 Const::from_bits(self.tcx, 0, self.param_env.and(ty))
146 Err(LitToConstError::TypeError) => bug!("const_eval_literal: had type error"),
150 crate fn pattern_from_hir(&mut self, p: &hir::Pat<'_>) -> Pat<'tcx> {
151 let p = match self.tcx.hir().get(p.hir_id) {
152 Node::Pat(p) | Node::Binding(p) => p,
153 node => bug!("pattern became {:?}", node),
155 Pat::from_hir(self.tcx, self.param_env, self.typeck_results(), p)
158 crate fn trait_method(
163 params: &[GenericArg<'tcx>],
164 ) -> &'tcx ty::Const<'tcx> {
165 let substs = self.tcx.mk_substs_trait(self_ty, params);
167 // The unhygienic comparison here is acceptable because this is only
168 // used on known traits.
171 .associated_items(trait_def_id)
172 .filter_by_name_unhygienic(method_name)
173 .find(|item| item.kind == ty::AssocKind::Fn)
174 .expect("trait method not found");
176 let method_ty = self.tcx.type_of(item.def_id);
177 let method_ty = method_ty.subst(self.tcx, substs);
178 ty::Const::zero_sized(self.tcx, method_ty)
181 crate fn all_fields(&mut self, adt_def: &ty::AdtDef, variant_index: VariantIdx) -> Vec<Field> {
182 (0..adt_def.variants[variant_index].fields.len()).map(Field::new).collect()
185 crate fn needs_drop(&mut self, ty: Ty<'tcx>) -> bool {
186 ty.needs_drop(self.tcx, self.param_env)
189 crate fn tcx(&self) -> TyCtxt<'tcx> {
193 crate fn typeck_results(&self) -> &'a ty::TypeckResults<'tcx> {
197 crate fn check_overflow(&self) -> bool {
201 crate fn type_is_copy_modulo_regions(&self, ty: Ty<'tcx>, span: Span) -> bool {
202 self.infcx.type_is_copy_modulo_regions(self.param_env, ty, span)
206 impl<'tcx> UserAnnotatedTyHelpers<'tcx> for Cx<'_, 'tcx> {
207 fn tcx(&self) -> TyCtxt<'tcx> {
211 fn typeck_results(&self) -> &ty::TypeckResults<'tcx> {
212 self.typeck_results()