src/librustc_mir/hair/cx/mod.rs

   1 //! This module contains the fcuntaiontliy to convert from the wacky tcx data
   2 //! structures into the HAIR. 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::hair::*;
   6 use crate::hair::util::UserAnnotatedTyHelpers;
   7
   8 use rustc_data_structures::indexed_vec::Idx;
   9 use rustc::hir::def_id::{DefId, LOCAL_CRATE};
  10 use rustc::hir::Node;
  11 use rustc::middle::region;
  12 use rustc::infer::InferCtxt;
  13 use rustc::ty::subst::Subst;
  14 use rustc::ty::{self, Ty, TyCtxt};
  15 use rustc::ty::subst::{Kind, Substs};
  16 use rustc::ty::layout::VariantIdx;
  17 use syntax::ast;
  18 use syntax::attr;
  19 use syntax::symbol::Symbol;
  20 use rustc::hir;
  21 use rustc_data_structures::sync::Lrc;
  22 use crate::hair::constant::{lit_to_const, LitToConstError};
  23
  24 #[derive(Clone)]
  25 pub struct Cx<'a, 'gcx: 'a + 'tcx, 'tcx: 'a> {
  26     tcx: TyCtxt<'a, 'gcx, 'tcx>,
  27     infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
  28
  29     pub root_lint_level: ast::NodeId,
  30     pub param_env: ty::ParamEnv<'gcx>,
  31
  32     /// Identity `Substs` for use with const-evaluation.
  33     pub identity_substs: &'gcx Substs<'gcx>,
  34
  35     pub region_scope_tree: Lrc<region::ScopeTree>,
  36     pub tables: &'a ty::TypeckTables<'gcx>,
  37
  38     /// This is `Constness::Const` if we are compiling a `static`,
  39     /// `const`, or the body of a `const fn`.
  40     constness: hir::Constness,
  41
  42     /// What kind of body is being compiled.
  43     pub body_owner_kind: hir::BodyOwnerKind,
  44
  45     /// Whether this constant/function needs overflow checks.
  46     check_overflow: bool,
  47
  48     /// See field with the same name on `Mir`.
  49     control_flow_destroyed: Vec<(Span, String)>,
  50 }
  51
  52 impl<'a, 'gcx, 'tcx> Cx<'a, 'gcx, 'tcx> {
  53     pub fn new(infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
  54                src_id: ast::NodeId) -> Cx<'a, 'gcx, 'tcx> {
  55         let tcx = infcx.tcx;
  56         let src_def_id = tcx.hir().local_def_id(src_id);
  57         let body_owner_kind = tcx.hir().body_owner_kind(src_id);
  58
  59         let constness = match body_owner_kind {
  60             hir::BodyOwnerKind::Const |
  61             hir::BodyOwnerKind::Static(_) => hir::Constness::Const,
  62             hir::BodyOwnerKind::Closure |
  63             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 = attr::contains_name(attrs, "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         let lint_level = lint_level_for_hir_id(tcx, src_id);
  80         Cx {
  81             tcx,
  82             infcx,
  83             root_lint_level: lint_level,
  84             param_env: tcx.param_env(src_def_id),
  85             identity_substs: Substs::identity_for_item(tcx.global_tcx(), src_def_id),
  86             region_scope_tree: tcx.region_scope_tree(src_def_id),
  87             tables: tcx.typeck_tables_of(src_def_id),
  88             constness,
  89             body_owner_kind,
  90             check_overflow,
  91             control_flow_destroyed: Vec::new(),
  92         }
  93     }
  94
  95     pub fn control_flow_destroyed(self) -> Vec<(Span, String)> {
  96         self.control_flow_destroyed
  97     }
  98 }
  99
 100 impl<'a, 'gcx, 'tcx> Cx<'a, 'gcx, 'tcx> {
 101     /// Normalizes `ast` into the appropriate "mirror" type.
 102     pub fn mirror<M: Mirror<'tcx>>(&mut self, ast: M) -> M::Output {
 103         ast.make_mirror(self)
 104     }
 105
 106     pub fn usize_ty(&mut self) -> Ty<'tcx> {
 107         self.tcx.types.usize
 108     }
 109
 110     pub fn usize_literal(&mut self, value: u64) -> &'tcx ty::LazyConst<'tcx> {
 111         self.tcx.mk_lazy_const(ty::LazyConst::Evaluated(ty::Const::from_usize(self.tcx, value)))
 112     }
 113
 114     pub fn bool_ty(&mut self) -> Ty<'tcx> {
 115         self.tcx.types.bool
 116     }
 117
 118     pub fn unit_ty(&mut self) -> Ty<'tcx> {
 119         self.tcx.mk_unit()
 120     }
 121
 122     pub fn true_literal(&mut self) -> &'tcx ty::LazyConst<'tcx> {
 123         self.tcx.mk_lazy_const(ty::LazyConst::Evaluated(ty::Const::from_bool(self.tcx, true)))
 124     }
 125
 126     pub fn false_literal(&mut self) -> &'tcx ty::LazyConst<'tcx> {
 127         self.tcx.mk_lazy_const(ty::LazyConst::Evaluated(ty::Const::from_bool(self.tcx, false)))
 128     }
 129
 130     pub fn const_eval_literal(
 131         &mut self,
 132         lit: &'tcx ast::LitKind,
 133         ty: Ty<'tcx>,
 134         sp: Span,
 135         neg: bool,
 136     ) -> ty::Const<'tcx> {
 137         trace!("const_eval_literal: {:#?}, {:?}, {:?}, {:?}", lit, ty, sp, neg);
 138
 139         match lit_to_const(lit, self.tcx, ty, neg) {
 140             Ok(c) => c,
 141             Err(LitToConstError::UnparseableFloat) => {
 142                 // FIXME(#31407) this is only necessary because float parsing is buggy
 143                 self.tcx.sess.span_err(sp, "could not evaluate float literal (see issue #31407)");
 144                 // create a dummy value and continue compiling
 145                 Const::from_bits(self.tcx, 0, self.param_env.and(ty))
 146             },
 147             Err(LitToConstError::Reported) => {
 148                 // create a dummy value and continue compiling
 149                 Const::from_bits(self.tcx, 0, self.param_env.and(ty))
 150             }
 151         }
 152     }
 153
 154     pub fn pattern_from_hir(&mut self, p: &hir::Pat) -> Pattern<'tcx> {
 155         let tcx = self.tcx.global_tcx();
 156         let p = match tcx.hir().get(p.id) {
 157             Node::Pat(p) | Node::Binding(p) => p,
 158             node => bug!("pattern became {:?}", node)
 159         };
 160         Pattern::from_hir(tcx,
 161                           self.param_env.and(self.identity_substs),
 162                           self.tables(),
 163                           p)
 164     }
 165
 166     pub fn trait_method(&mut self,
 167                         trait_def_id: DefId,
 168                         method_name: &str,
 169                         self_ty: Ty<'tcx>,
 170                         params: &[Kind<'tcx>])
 171                         -> (Ty<'tcx>, ty::Const<'tcx>) {
 172         let method_name = Symbol::intern(method_name);
 173         let substs = self.tcx.mk_substs_trait(self_ty, params);
 174         for item in self.tcx.associated_items(trait_def_id) {
 175             if item.kind == ty::AssociatedKind::Method && item.ident.name == method_name {
 176                 let method_ty = self.tcx.type_of(item.def_id);
 177                 let method_ty = method_ty.subst(self.tcx, substs);
 178                 return (method_ty, ty::Const::zero_sized(method_ty));
 179             }
 180         }
 181
 182         bug!("found no method `{}` in `{:?}`", method_name, trait_def_id);
 183     }
 184
 185     pub fn all_fields(&mut self, adt_def: &ty::AdtDef, variant_index: VariantIdx) -> Vec<Field> {
 186         (0..adt_def.variants[variant_index].fields.len())
 187             .map(Field::new)
 188             .collect()
 189     }
 190
 191     pub fn needs_drop(&mut self, ty: Ty<'tcx>) -> bool {
 192         let (ty, param_env) = self.tcx.lift_to_global(&(ty, self.param_env)).unwrap_or_else(|| {
 193             bug!("MIR: Cx::needs_drop({:?}, {:?}) got \
 194                   type with inference types/regions",
 195                  ty, self.param_env);
 196         });
 197         ty.needs_drop(self.tcx.global_tcx(), param_env)
 198     }
 199
 200     fn lint_level_of(&self, node_id: ast::NodeId) -> LintLevel {
 201         let hir_id = self.tcx.hir().definitions().node_to_hir_id(node_id);
 202         let has_lint_level = self.tcx.dep_graph.with_ignore(|| {
 203             self.tcx.lint_levels(LOCAL_CRATE).lint_level_set(hir_id).is_some()
 204         });
 205
 206         if has_lint_level {
 207             LintLevel::Explicit(node_id)
 208         } else {
 209             LintLevel::Inherited
 210         }
 211     }
 212
 213     pub fn tcx(&self) -> TyCtxt<'a, 'gcx, 'tcx> {
 214         self.tcx
 215     }
 216
 217     pub fn tables(&self) -> &'a ty::TypeckTables<'gcx> {
 218         self.tables
 219     }
 220
 221     pub fn check_overflow(&self) -> bool {
 222         self.check_overflow
 223     }
 224
 225     pub fn type_is_copy_modulo_regions(&self, ty: Ty<'tcx>, span: Span) -> bool {
 226         self.infcx.type_is_copy_modulo_regions(self.param_env, ty, span)
 227     }
 228 }
 229
 230 impl UserAnnotatedTyHelpers<'gcx, 'tcx> for Cx<'_, 'gcx, 'tcx> {
 231     fn tcx(&self) -> TyCtxt<'_, 'gcx, 'tcx> {
 232         self.tcx()
 233     }
 234
 235     fn tables(&self) -> &ty::TypeckTables<'tcx> {
 236         self.tables()
 237     }
 238 }
 239
 240 fn lint_level_for_hir_id(tcx: TyCtxt<'_, '_, '_>, mut id: ast::NodeId) -> ast::NodeId {
 241     // Right now we insert a `with_ignore` node in the dep graph here to
 242     // ignore the fact that `lint_levels` below depends on the entire crate.
 243     // For now this'll prevent false positives of recompiling too much when
 244     // anything changes.
 245     //
 246     // Once red/green incremental compilation lands we should be able to
 247     // remove this because while the crate changes often the lint level map
 248     // will change rarely.
 249     tcx.dep_graph.with_ignore(|| {
 250         let sets = tcx.lint_levels(LOCAL_CRATE);
 251         loop {
 252             let hir_id = tcx.hir().definitions().node_to_hir_id(id);
 253             if sets.lint_level_set(hir_id).is_some() {
 254                 return id
 255             }
 256             let next = tcx.hir().get_parent_node(id);
 257             if next == id {
 258                 bug!("lint traversal reached the root of the crate");
 259             }
 260             id = next;
 261         }
 262     })
 263 }
 264
 265 mod block;
 266 mod expr;
 267 mod to_ref;