compiler/rustc_mir_build/src/thir/cx/mod.rs

   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.
   4
   5 use crate::thir::util::UserAnnotatedTyHelpers;
   6 use crate::thir::*;
   7
   8 use rustc_ast as ast;
   9 use rustc_hir as hir;
  10 use rustc_hir::def_id::{DefId, LocalDefId};
  11 use rustc_hir::Node;
  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;
  22
  23 #[derive(Clone)]
  24 crate struct Cx<'a, 'tcx> {
  25     tcx: TyCtxt<'tcx>,
  26     infcx: &'a InferCtxt<'a, 'tcx>,
  27
  28     crate root_lint_level: hir::HirId,
  29     crate param_env: ty::ParamEnv<'tcx>,
  30
  31     /// Identity `InternalSubsts` for use with const-evaluation.
  32     crate identity_substs: &'tcx InternalSubsts<'tcx>,
  33
  34     crate region_scope_tree: &'tcx region::ScopeTree,
  35     crate typeck_results: &'a ty::TypeckResults<'tcx>,
  36
  37     /// This is `Constness::Const` if we are compiling a `static`,
  38     /// `const`, or the body of a `const fn`.
  39     constness: hir::Constness,
  40
  41     /// The `DefId` of the owner of this body.
  42     body_owner: DefId,
  43
  44     /// What kind of body is being compiled.
  45     crate body_owner_kind: hir::BodyOwnerKind,
  46
  47     /// Whether this constant/function needs overflow checks.
  48     check_overflow: bool,
  49 }
  50
  51 impl<'a, 'tcx> Cx<'a, 'tcx> {
  52     crate fn new(
  53         infcx: &'a InferCtxt<'a, 'tcx>,
  54         def: ty::WithOptConstParam<LocalDefId>,
  55         src_id: hir::HirId,
  56     ) -> Cx<'a, 'tcx> {
  57         let tcx = infcx.tcx;
  58         let typeck_results = tcx.typeck_opt_const_arg(def);
  59         let body_owner_kind = tcx.hir().body_owner_kind(src_id);
  60
  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,
  64         };
  65
  66         let attrs = tcx.hir().attrs(src_id);
  67
  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);
  72
  73         // Respect -C overflow-checks.
  74         check_overflow |= tcx.sess.overflow_checks();
  75
  76         // Constants always need overflow checks.
  77         check_overflow |= constness == hir::Constness::Const;
  78
  79         Cx {
  80             tcx,
  81             infcx,
  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),
  86             typeck_results,
  87             constness,
  88             body_owner: def.did.to_def_id(),
  89             body_owner_kind,
  90             check_overflow,
  91         }
  92     }
  93 }
  94
  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 {
  98         ast.make_mirror(self)
  99     }
 100
 101     crate fn usize_ty(&mut self) -> Ty<'tcx> {
 102         self.tcx.types.usize
 103     }
 104
 105     crate fn usize_literal(&mut self, value: u64) -> &'tcx ty::Const<'tcx> {
 106         ty::Const::from_usize(self.tcx, value)
 107     }
 108
 109     crate fn bool_ty(&mut self) -> Ty<'tcx> {
 110         self.tcx.types.bool
 111     }
 112
 113     crate fn unit_ty(&mut self) -> Ty<'tcx> {
 114         self.tcx.mk_unit()
 115     }
 116
 117     crate fn true_literal(&mut self) -> &'tcx ty::Const<'tcx> {
 118         ty::Const::from_bool(self.tcx, true)
 119     }
 120
 121     crate fn false_literal(&mut self) -> &'tcx ty::Const<'tcx> {
 122         ty::Const::from_bool(self.tcx, false)
 123     }
 124
 125     crate fn const_eval_literal(
 126         &mut self,
 127         lit: &'tcx ast::LitKind,
 128         ty: Ty<'tcx>,
 129         sp: Span,
 130         neg: bool,
 131     ) -> &'tcx ty::Const<'tcx> {
 132         trace!("const_eval_literal: {:#?}, {:?}, {:?}, {:?}", lit, ty, sp, neg);
 133
 134         match self.tcx.at(sp).lit_to_const(LitToConstInput { lit, ty, neg }) {
 135             Ok(c) => c,
 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))
 141             }
 142             Err(LitToConstError::Reported) => {
 143                 // create a dummy value and continue compiling
 144                 Const::from_bits(self.tcx, 0, self.param_env.and(ty))
 145             }
 146             Err(LitToConstError::TypeError) => bug!("const_eval_literal: had type error"),
 147         }
 148     }
 149
 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),
 154         };
 155         Pat::from_hir(self.tcx, self.param_env, self.typeck_results(), p)
 156     }
 157
 158     crate fn trait_method(
 159         &mut self,
 160         trait_def_id: DefId,
 161         method_name: Symbol,
 162         self_ty: Ty<'tcx>,
 163         params: &[GenericArg<'tcx>],
 164     ) -> &'tcx ty::Const<'tcx> {
 165         let substs = self.tcx.mk_substs_trait(self_ty, params);
 166
 167         // The unhygienic comparison here is acceptable because this is only
 168         // used on known traits.
 169         let item = self
 170             .tcx
 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");
 175
 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)
 179     }
 180
 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()
 183     }
 184
 185     crate fn needs_drop(&mut self, ty: Ty<'tcx>) -> bool {
 186         ty.needs_drop(self.tcx, self.param_env)
 187     }
 188
 189     crate fn tcx(&self) -> TyCtxt<'tcx> {
 190         self.tcx
 191     }
 192
 193     crate fn typeck_results(&self) -> &'a ty::TypeckResults<'tcx> {
 194         self.typeck_results
 195     }
 196
 197     crate fn check_overflow(&self) -> bool {
 198         self.check_overflow
 199     }
 200
 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)
 203     }
 204 }
 205
 206 impl<'tcx> UserAnnotatedTyHelpers<'tcx> for Cx<'_, 'tcx> {
 207     fn tcx(&self) -> TyCtxt<'tcx> {
 208         self.tcx()
 209     }
 210
 211     fn typeck_results(&self) -> &ty::TypeckResults<'tcx> {
 212         self.typeck_results()
 213     }
 214 }
 215
 216 mod block;
 217 mod expr;
 218 mod to_ref;