src/librustc_mir/hair/cx/mod.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! This module contains the code to convert from the wacky tcx data
  12 //! structures into the hair. The `builder` is generally ignorant of
  13 //! the tcx etc, and instead goes through the `Cx` for most of its
  14 //! work.
  15 //!
  16
  17 use hair::*;
  18 use rustc::mir::transform::MirSource;
  19
  20 use rustc::middle::const_val::{ConstEvalErr, ConstVal};
  21 use rustc_const_eval::ConstContext;
  22 use rustc_data_structures::indexed_vec::Idx;
  23 use rustc::hir::def_id::DefId;
  24 use rustc::hir::map::blocks::FnLikeNode;
  25 use rustc::middle::region::RegionMaps;
  26 use rustc::infer::InferCtxt;
  27 use rustc::ty::subst::Subst;
  28 use rustc::ty::{self, Ty, TyCtxt};
  29 use syntax::symbol::Symbol;
  30 use rustc::hir;
  31 use rustc_const_math::{ConstInt, ConstUsize};
  32 use std::rc::Rc;
  33
  34 #[derive(Clone)]
  35 pub struct Cx<'a, 'gcx: 'a + 'tcx, 'tcx: 'a> {
  36     tcx: TyCtxt<'a, 'gcx, 'tcx>,
  37     infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
  38     pub param_env: ty::ParamEnv<'tcx>,
  39     pub region_maps: Rc<RegionMaps>,
  40
  41     /// This is `Constness::Const` if we are compiling a `static`,
  42     /// `const`, or the body of a `const fn`.
  43     constness: hir::Constness,
  44
  45     /// What are we compiling?
  46     pub src: MirSource,
  47
  48     /// True if this constant/function needs overflow checks.
  49     check_overflow: bool,
  50 }
  51
  52 impl<'a, 'gcx, 'tcx> Cx<'a, 'gcx, 'tcx> {
  53     pub fn new(infcx: &'a InferCtxt<'a, 'gcx, 'tcx>, src: MirSource) -> Cx<'a, 'gcx, 'tcx> {
  54         let constness = match src {
  55             MirSource::Const(_) |
  56             MirSource::Static(..) => hir::Constness::Const,
  57             MirSource::Fn(id) => {
  58                 let fn_like = FnLikeNode::from_node(infcx.tcx.hir.get(id));
  59                 fn_like.map_or(hir::Constness::NotConst, |f| f.constness())
  60             }
  61             MirSource::Promoted(..) => bug!(),
  62         };
  63
  64         let tcx = infcx.tcx;
  65         let src_id = src.item_id();
  66         let src_def_id = tcx.hir.local_def_id(src_id);
  67
  68         let param_env = tcx.param_env(src_def_id);
  69         let region_maps = tcx.region_maps(src_def_id);
  70
  71         let attrs = tcx.hir.attrs(src_id);
  72
  73         // Some functions always have overflow checks enabled,
  74         // however, they may not get codegen'd, depending on
  75         // the settings for the crate they are translated in.
  76         let mut check_overflow = attrs.iter()
  77             .any(|item| item.check_name("rustc_inherit_overflow_checks"));
  78
  79         // Respect -C overflow-checks.
  80         check_overflow |= tcx.sess.overflow_checks();
  81
  82         // Constants and const fn's always need overflow checks.
  83         check_overflow |= constness == hir::Constness::Const;
  84
  85         Cx { tcx, infcx, param_env, region_maps, constness, src, check_overflow }
  86     }
  87 }
  88
  89 impl<'a, 'gcx, 'tcx> Cx<'a, 'gcx, 'tcx> {
  90     /// Normalizes `ast` into the appropriate `mirror` type.
  91     pub fn mirror<M: Mirror<'tcx>>(&mut self, ast: M) -> M::Output {
  92         ast.make_mirror(self)
  93     }
  94
  95     pub fn usize_ty(&mut self) -> Ty<'tcx> {
  96         self.tcx.types.usize
  97     }
  98
  99     pub fn usize_literal(&mut self, value: u64) -> Literal<'tcx> {
 100         match ConstUsize::new(value, self.tcx.sess.target.uint_type) {
 101             Ok(val) => Literal::Value { value: ConstVal::Integral(ConstInt::Usize(val)) },
 102             Err(_) => bug!("usize literal out of range for target"),
 103         }
 104     }
 105
 106     pub fn bool_ty(&mut self) -> Ty<'tcx> {
 107         self.tcx.types.bool
 108     }
 109
 110     pub fn unit_ty(&mut self) -> Ty<'tcx> {
 111         self.tcx.mk_nil()
 112     }
 113
 114     pub fn true_literal(&mut self) -> Literal<'tcx> {
 115         Literal::Value { value: ConstVal::Bool(true) }
 116     }
 117
 118     pub fn false_literal(&mut self) -> Literal<'tcx> {
 119         Literal::Value { value: ConstVal::Bool(false) }
 120     }
 121
 122     pub fn const_eval_literal(&mut self, e: &hir::Expr) -> Literal<'tcx> {
 123         let tcx = self.tcx.global_tcx();
 124         match ConstContext::with_tables(tcx, self.tables()).eval(e) {
 125             Ok(value) => Literal::Value { value: value },
 126             Err(s) => self.fatal_const_eval_err(&s, e.span, "expression")
 127         }
 128     }
 129
 130     pub fn fatal_const_eval_err(&self,
 131         err: &ConstEvalErr<'tcx>,
 132         primary_span: Span,
 133         primary_kind: &str)
 134         -> !
 135     {
 136         err.report(self.tcx, primary_span, primary_kind);
 137         self.tcx.sess.abort_if_errors();
 138         unreachable!()
 139     }
 140
 141     pub fn trait_method(&mut self,
 142                         trait_def_id: DefId,
 143                         method_name: &str,
 144                         self_ty: Ty<'tcx>,
 145                         params: &[Ty<'tcx>])
 146                         -> (Ty<'tcx>, Literal<'tcx>) {
 147         let method_name = Symbol::intern(method_name);
 148         let substs = self.tcx.mk_substs_trait(self_ty, params);
 149         for item in self.tcx.associated_items(trait_def_id) {
 150             if item.kind == ty::AssociatedKind::Method && item.name == method_name {
 151                 let method_ty = self.tcx.type_of(item.def_id);
 152                 let method_ty = method_ty.subst(self.tcx, substs);
 153                 return (method_ty,
 154                         Literal::Value {
 155                             value: ConstVal::Function(item.def_id, substs),
 156                         });
 157             }
 158         }
 159
 160         bug!("found no method `{}` in `{:?}`", method_name, trait_def_id);
 161     }
 162
 163     pub fn num_variants(&mut self, adt_def: &ty::AdtDef) -> usize {
 164         adt_def.variants.len()
 165     }
 166
 167     pub fn all_fields(&mut self, adt_def: &ty::AdtDef, variant_index: usize) -> Vec<Field> {
 168         (0..adt_def.variants[variant_index].fields.len())
 169             .map(Field::new)
 170             .collect()
 171     }
 172
 173     pub fn needs_drop(&mut self, ty: Ty<'tcx>) -> bool {
 174         let (ty, param_env) = self.tcx.lift_to_global(&(ty, self.param_env)).unwrap_or_else(|| {
 175             bug!("MIR: Cx::needs_drop({:?}, {:?}) got \
 176                   type with inference types/regions",
 177                  ty, self.param_env);
 178         });
 179         ty.needs_drop(self.tcx.global_tcx(), param_env)
 180     }
 181
 182     pub fn tcx(&self) -> TyCtxt<'a, 'gcx, 'tcx> {
 183         self.tcx
 184     }
 185
 186     pub fn tables(&self) -> &'a ty::TypeckTables<'gcx> {
 187         self.infcx.tables.expect_interned()
 188     }
 189
 190     pub fn check_overflow(&self) -> bool {
 191         self.check_overflow
 192     }
 193 }
 194
 195 mod block;
 196 mod expr;
 197 mod to_ref;