src/librustc/ty/flags.rs

   1 // Copyright 2012-2015 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 use ty::subst::Substs;
  12 use ty::{self, Ty, TypeFlags, TypeFoldable};
  13
  14 pub struct FlagComputation {
  15     pub flags: TypeFlags,
  16
  17     // maximum depth of any bound region that we have seen thus far
  18     pub depth: u32,
  19 }
  20
  21 impl FlagComputation {
  22     fn new() -> FlagComputation {
  23         FlagComputation { flags: TypeFlags::empty(), depth: 0 }
  24     }
  25
  26     pub fn for_sty(st: &ty::TypeVariants) -> FlagComputation {
  27         let mut result = FlagComputation::new();
  28         result.add_sty(st);
  29         result
  30     }
  31
  32     fn add_flags(&mut self, flags: TypeFlags) {
  33         self.flags = self.flags | (flags & TypeFlags::NOMINAL_FLAGS);
  34     }
  35
  36     fn add_depth(&mut self, depth: u32) {
  37         if depth > self.depth {
  38             self.depth = depth;
  39         }
  40     }
  41
  42     /// Adds the flags/depth from a set of types that appear within the current type, but within a
  43     /// region binder.
  44     fn add_bound_computation(&mut self, computation: &FlagComputation) {
  45         self.add_flags(computation.flags);
  46
  47         // The types that contributed to `computation` occurred within
  48         // a region binder, so subtract one from the region depth
  49         // within when adding the depth to `self`.
  50         let depth = computation.depth;
  51         if depth > 0 {
  52             self.add_depth(depth - 1);
  53         }
  54     }
  55
  56     fn add_sty(&mut self, st: &ty::TypeVariants) {
  57         match st {
  58             &ty::TyBool |
  59             &ty::TyChar |
  60             &ty::TyInt(_) |
  61             &ty::TyFloat(_) |
  62             &ty::TyUint(_) |
  63             &ty::TyNever |
  64             &ty::TyStr => {
  65             }
  66
  67             // You might think that we could just return TyError for
  68             // any type containing TyError as a component, and get
  69             // rid of the TypeFlags::HAS_TY_ERR flag -- likewise for ty_bot (with
  70             // the exception of function types that return bot).
  71             // But doing so caused sporadic memory corruption, and
  72             // neither I (tjc) nor nmatsakis could figure out why,
  73             // so we're doing it this way.
  74             &ty::TyError => {
  75                 self.add_flags(TypeFlags::HAS_TY_ERR)
  76             }
  77
  78             &ty::TyParam(ref p) => {
  79                 self.add_flags(TypeFlags::HAS_LOCAL_NAMES);
  80                 if p.is_self() {
  81                     self.add_flags(TypeFlags::HAS_SELF);
  82                 } else {
  83                     self.add_flags(TypeFlags::HAS_PARAMS);
  84                 }
  85             }
  86
  87             &ty::TyClosure(_, ref substs) => {
  88                 self.add_flags(TypeFlags::HAS_TY_CLOSURE);
  89                 self.add_flags(TypeFlags::HAS_LOCAL_NAMES);
  90                 self.add_substs(&substs.func_substs);
  91                 self.add_tys(&substs.upvar_tys);
  92             }
  93
  94             &ty::TyInfer(infer) => {
  95                 self.add_flags(TypeFlags::HAS_LOCAL_NAMES); // it might, right?
  96                 self.add_flags(TypeFlags::HAS_TY_INFER);
  97                 match infer {
  98                     ty::FreshTy(_) |
  99                     ty::FreshIntTy(_) |
 100                     ty::FreshFloatTy(_) => {}
 101                     _ => self.add_flags(TypeFlags::KEEP_IN_LOCAL_TCX)
 102                 }
 103             }
 104
 105             &ty::TyAdt(_, substs) => {
 106                 self.add_substs(substs);
 107             }
 108
 109             &ty::TyProjection(ref data) => {
 110                 // currently we can't normalize projections that
 111                 // include bound regions, so track those separately.
 112                 if !data.has_escaping_regions() {
 113                     self.add_flags(TypeFlags::HAS_NORMALIZABLE_PROJECTION);
 114                 }
 115                 self.add_flags(TypeFlags::HAS_PROJECTION);
 116                 self.add_projection_ty(data);
 117             }
 118
 119             &ty::TyAnon(_, substs) => {
 120                 self.add_flags(TypeFlags::HAS_PROJECTION);
 121                 self.add_substs(substs);
 122             }
 123
 124             &ty::TyTrait(ref obj) => {
 125                 let mut computation = FlagComputation::new();
 126                 computation.add_substs(obj.principal.skip_binder().substs);
 127                 for projection_bound in &obj.projection_bounds {
 128                     let mut proj_computation = FlagComputation::new();
 129                     proj_computation.add_existential_projection(&projection_bound.0);
 130                     self.add_bound_computation(&proj_computation);
 131                 }
 132                 self.add_bound_computation(&computation);
 133                 self.add_region(obj.region_bound);
 134             }
 135
 136             &ty::TyBox(tt) | &ty::TyArray(tt, _) | &ty::TySlice(tt) => {
 137                 self.add_ty(tt)
 138             }
 139
 140             &ty::TyRawPtr(ref m) => {
 141                 self.add_ty(m.ty);
 142             }
 143
 144             &ty::TyRef(r, ref m) => {
 145                 self.add_region(r);
 146                 self.add_ty(m.ty);
 147             }
 148
 149             &ty::TyTuple(ref ts) => {
 150                 self.add_tys(&ts[..]);
 151             }
 152
 153             &ty::TyFnDef(_, substs, ref f) => {
 154                 self.add_substs(substs);
 155                 self.add_fn_sig(&f.sig);
 156             }
 157
 158             &ty::TyFnPtr(ref f) => {
 159                 self.add_fn_sig(&f.sig);
 160             }
 161         }
 162     }
 163
 164     fn add_ty(&mut self, ty: Ty) {
 165         self.add_flags(ty.flags.get());
 166         self.add_depth(ty.region_depth);
 167     }
 168
 169     fn add_tys(&mut self, tys: &[Ty]) {
 170         for &ty in tys {
 171             self.add_ty(ty);
 172         }
 173     }
 174
 175     fn add_fn_sig(&mut self, fn_sig: &ty::PolyFnSig) {
 176         let mut computation = FlagComputation::new();
 177
 178         computation.add_tys(&fn_sig.0.inputs);
 179         computation.add_ty(fn_sig.0.output);
 180
 181         self.add_bound_computation(&computation);
 182     }
 183
 184     fn add_region(&mut self, r: &ty::Region) {
 185         match *r {
 186             ty::ReVar(..) => {
 187                 self.add_flags(TypeFlags::HAS_RE_INFER);
 188                 self.add_flags(TypeFlags::KEEP_IN_LOCAL_TCX);
 189             }
 190             ty::ReSkolemized(..) => {
 191                 self.add_flags(TypeFlags::HAS_RE_INFER);
 192                 self.add_flags(TypeFlags::HAS_RE_SKOL);
 193                 self.add_flags(TypeFlags::KEEP_IN_LOCAL_TCX);
 194             }
 195             ty::ReLateBound(debruijn, _) => { self.add_depth(debruijn.depth); }
 196             ty::ReEarlyBound(..) => { self.add_flags(TypeFlags::HAS_RE_EARLY_BOUND); }
 197             ty::ReStatic | ty::ReErased => {}
 198             _ => { self.add_flags(TypeFlags::HAS_FREE_REGIONS); }
 199         }
 200
 201         if !r.is_global() {
 202             self.add_flags(TypeFlags::HAS_LOCAL_NAMES);
 203         }
 204     }
 205
 206     fn add_existential_projection(&mut self, projection: &ty::ExistentialProjection) {
 207         self.add_substs(projection.trait_ref.substs);
 208         self.add_ty(projection.ty);
 209     }
 210
 211     fn add_projection_ty(&mut self, projection_ty: &ty::ProjectionTy) {
 212         self.add_substs(projection_ty.trait_ref.substs);
 213     }
 214
 215     fn add_substs(&mut self, substs: &Substs) {
 216         for ty in substs.types() {
 217             self.add_ty(ty);
 218         }
 219
 220         for r in substs.regions() {
 221             self.add_region(r);
 222         }
 223     }
 224 }