rustc: reduce Substs and Generics to a simple immutable API.

Author: eddyb

src/librustc/infer/error_reporting.rs

@@ -1366,7 +1366,7 @@ impl<'a, 'gcx, 'tcx> Rebuilder<'a, 'gcx, 'tcx> {
                 hir::TyPath(ref maybe_qself, ref path) => {
                     match self.tcx.expect_def(cur_ty.id) {
                         Def::Enum(did) | Def::TyAlias(did) | Def::Struct(did) => {
-                            let generics = self.tcx.lookup_item_type(did).generics;
+                            let generics = self.tcx.lookup_generics(did);
 
                             let expected =
                                 generics.regions.len(subst::TypeSpace) as u32;

src/librustc/infer/mod.rs

@@ -25,9 +25,7 @@ use middle::mem_categorization as mc;
 use middle::mem_categorization::McResult;
 use middle::region::CodeExtent;
 use mir::tcx::LvalueTy;
-use ty::subst;
-use ty::subst::Substs;
-use ty::subst::Subst;
+use ty::subst::{Subst, Substs};
 use ty::adjustment;
 use ty::{TyVid, IntVid, FloatVid};
 use ty::{self, Ty, TyCtxt};
@@ -1236,43 +1234,15 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
 
     /// Given a set of generics defined on a type or impl, returns a substitution mapping each
     /// type/region parameter to a fresh inference variable.
-    pub fn fresh_substs_for_generics(&self,
-                                     span: Span,
-                                     generics: &ty::Generics<'tcx>)
-                                     -> &'tcx subst::Substs<'tcx>
-    {
-        let substs = Substs::from_generics(generics, |def, _| {
+    pub fn fresh_substs_for_item(&self,
+                                 span: Span,
+                                 def_id: DefId)
+                                 -> &'tcx Substs<'tcx> {
+        Substs::for_item(self.tcx, def_id, |def, _| {
             self.region_var_for_def(span, def)
         }, |def, substs| {
             self.type_var_for_def(span, def, substs)
-        });
-
-        self.tcx.mk_substs(substs)
-    }
-
-    /// Given a set of generics defined on a trait, returns a substitution mapping each output
-    /// type/region parameter to a fresh inference variable, and mapping the self type to
-    /// `self_ty`.
-    pub fn fresh_substs_for_trait(&self,
-                                  span: Span,
-                                  generics: &ty::Generics<'tcx>,
-                                  self_ty: Ty<'tcx>)
-                                  -> &'tcx subst::Substs<'tcx>
-    {
-        assert!(generics.types.len(subst::SelfSpace) == 1);
-        assert!(generics.types.len(subst::FnSpace) == 0);
-
-        let substs = Substs::from_generics(generics, |def, _| {
-            self.region_var_for_def(span, def)
-        }, |def, substs| {
-            if def.space == subst::SelfSpace {
-                self_ty
-            } else {
-                self.type_var_for_def(span, def, substs)
-            }
-        });
-
-        self.tcx.mk_substs(substs)
+        })
     }
 
     pub fn fresh_bound_region(&self, debruijn: ty::DebruijnIndex) -> ty::Region {

src/librustc/middle/cstore.rs

@@ -154,14 +154,16 @@ pub trait CrateStore<'tcx> {
     fn item_variances(&self, def: DefId) -> ty::ItemVariances;
     fn repr_attrs(&self, def: DefId) -> Vec<attr::ReprAttr>;
     fn item_type<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
-                     -> ty::TypeScheme<'tcx>;
+                     -> Ty<'tcx>;
     fn visible_parent_map<'a>(&'a self) -> ::std::cell::RefMut<'a, DefIdMap<DefId>>;
     fn item_name(&self, def: DefId) -> ast::Name;
     fn opt_item_name(&self, def: DefId) -> Option<ast::Name>;
     fn item_predicates<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
                            -> ty::GenericPredicates<'tcx>;
     fn item_super_predicates<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
                                  -> ty::GenericPredicates<'tcx>;
+    fn item_generics<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
+                         -> &'tcx ty::Generics<'tcx>;
     fn item_attrs(&self, def_id: DefId) -> Vec<ast::Attribute>;
     fn trait_def<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)-> ty::TraitDef<'tcx>;
     fn adt_def<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId) -> ty::AdtDefMaster<'tcx>;
@@ -187,8 +189,7 @@ pub trait CrateStore<'tcx> {
     fn impl_parent(&self, impl_def_id: DefId) -> Option<DefId>;
 
     // trait/impl-item info
-    fn trait_of_item<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId)
-                         -> Option<DefId>;
+    fn trait_of_item(&self, def_id: DefId) -> Option<DefId>;
     fn impl_or_trait_item<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
                               -> Option<ty::ImplOrTraitItem<'tcx>>;
 
@@ -334,7 +335,7 @@ impl<'tcx> CrateStore<'tcx> for DummyCrateStore {
     fn item_variances(&self, def: DefId) -> ty::ItemVariances { bug!("item_variances") }
     fn repr_attrs(&self, def: DefId) -> Vec<attr::ReprAttr> { bug!("repr_attrs") }
     fn item_type<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
-                     -> ty::TypeScheme<'tcx> { bug!("item_type") }
+                     -> Ty<'tcx> { bug!("item_type") }
     fn visible_parent_map<'a>(&'a self) -> ::std::cell::RefMut<'a, DefIdMap<DefId>> {
         bug!("visible_parent_map")
     }
@@ -344,6 +345,8 @@ impl<'tcx> CrateStore<'tcx> for DummyCrateStore {
                            -> ty::GenericPredicates<'tcx> { bug!("item_predicates") }
     fn item_super_predicates<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
                                  -> ty::GenericPredicates<'tcx> { bug!("item_super_predicates") }
+    fn item_generics<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
+                         -> &'tcx ty::Generics<'tcx> { bug!("item_generics") }
     fn item_attrs(&self, def_id: DefId) -> Vec<ast::Attribute> { bug!("item_attrs") }
     fn trait_def<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)-> ty::TraitDef<'tcx>
         { bug!("trait_def") }
@@ -379,8 +382,7 @@ impl<'tcx> CrateStore<'tcx> for DummyCrateStore {
     fn impl_parent(&self, def: DefId) -> Option<DefId> { bug!("impl_parent") }
 
     // trait/impl-item info
-    fn trait_of_item<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId)
-                         -> Option<DefId> { bug!("trait_of_item") }
+    fn trait_of_item(&self, def_id: DefId) -> Option<DefId> { bug!("trait_of_item") }
     fn impl_or_trait_item<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
                               -> Option<ty::ImplOrTraitItem<'tcx>> { bug!("impl_or_trait_item") }
 
@@ -583,7 +585,7 @@ pub mod tls {
     pub trait DecodingContext<'tcx> {
         fn tcx<'a>(&'a self) -> TyCtxt<'a, 'tcx, 'tcx>;
         fn decode_ty(&self, decoder: &mut OpaqueDecoder) -> ty::Ty<'tcx>;
-        fn decode_substs(&self, decoder: &mut OpaqueDecoder) -> Substs<'tcx>;
+        fn decode_substs(&self, decoder: &mut OpaqueDecoder) -> &'tcx Substs<'tcx>;
         fn translate_def_id(&self, def_id: DefId) -> DefId;
     }
 

src/librustc/middle/dead.rs

@@ -18,7 +18,7 @@ use hir::{self, pat_util, PatKind};
 use hir::intravisit::{self, Visitor};
 
 use middle::privacy;
-use ty::{self, TyCtxt};
+use ty::{self, subst, TyCtxt};
 use hir::def::Def;
 use hir::def_id::{DefId};
 use lint;
@@ -88,15 +88,24 @@ impl<'a, 'tcx> MarkSymbolVisitor<'a, 'tcx> {
     fn lookup_and_handle_definition(&mut self, id: ast::NodeId) {
         use ty::TypeVariants::{TyEnum, TyStruct};
 
+        let def = self.tcx.expect_def(id);
+
         // If `bar` is a trait item, make sure to mark Foo as alive in `Foo::bar`
-        self.tcx.tables.borrow().item_substs.get(&id)
-            .and_then(|substs| substs.substs.self_ty())
-            .map(|ty| match ty.sty {
-                TyEnum(tyid, _) | TyStruct(tyid, _) => self.check_def_id(tyid.did),
-                _ => (),
-            });
+        match def {
+            Def::AssociatedTy(..) | Def::Method(_) | Def::AssociatedConst(_)
+            if self.tcx.trait_of_item(def.def_id()).is_some() => {
+                if let Some(substs) = self.tcx.tables.borrow().item_substs.get(&id) {
+                    match substs.substs.types.get(subst::SelfSpace, 0).sty {
+                        TyEnum(tyid, _) | TyStruct(tyid, _) => {
+                            self.check_def_id(tyid.did)
+                        }
+                        _ => {}
+                    }
+                }
+            }
+            _ => {}
+        }
 
-        let def = self.tcx.expect_def(id);
         match def {
             Def::Const(_) | Def::AssociatedConst(..) => {
                 self.check_def_id(def.def_id());

src/librustc/mir/repr.rs

@@ -1073,10 +1073,7 @@ impl<'tcx> Debug for Rvalue<'tcx> {
                         let variant_def = &adt_def.variants[variant];
 
                         ppaux::parameterized(fmt, substs, variant_def.did,
-                                             ppaux::Ns::Value, &[],
-                                             |tcx| {
-                            Some(tcx.lookup_item_type(variant_def.did).generics)
-                        })?;
+                                             ppaux::Ns::Value, &[])?;
 
                         match variant_def.kind {
                             ty::VariantKind::Unit => Ok(()),
@@ -1169,9 +1166,7 @@ impl<'tcx> Debug for Literal<'tcx> {
         use self::Literal::*;
         match *self {
             Item { def_id, substs } => {
-                ppaux::parameterized(
-                    fmt, substs, def_id, ppaux::Ns::Value, &[],
-                    |tcx| Some(tcx.lookup_item_type(def_id).generics))
+                ppaux::parameterized(fmt, substs, def_id, ppaux::Ns::Value, &[])
             }
             Value { ref value } => {
                 write!(fmt, "const ")?;

src/librustc/traits/error_reporting.rs

@@ -221,9 +221,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
 
         self.tcx.lookup_trait_def(trait_ref.def_id)
             .for_each_relevant_impl(self.tcx, trait_self_ty, |def_id| {
-                let ity = tcx.lookup_item_type(def_id);
-                let impl_substs = self.fresh_substs_for_generics(obligation.cause.span,
-                                                                 &ity.generics);
+                let impl_substs = self.fresh_substs_for_item(obligation.cause.span, def_id);
                 let impl_trait_ref = tcx
                     .impl_trait_ref(def_id)
                     .unwrap()

src/librustc/traits/fulfill.rs

@@ -160,10 +160,9 @@ impl<'a, 'gcx, 'tcx> DeferredObligation<'tcx> {
             // We can resolve the `impl Trait` to its concrete type.
             if let Some(ty_scheme) = tcx.opt_lookup_item_type(def_id) {
                 let concrete_ty = ty_scheme.ty.subst(tcx, substs);
-                let concrete_substs = Substs::new_trait(vec![], vec![], concrete_ty);
                 let predicate = ty::TraitRef {
                     def_id: self.predicate.def_id(),
-                    substs: tcx.mk_substs(concrete_substs)
+                    substs: Substs::new_trait(tcx, vec![], vec![], concrete_ty)
                 }.to_predicate();
 
                 let original_obligation = Obligation::new(self.cause.clone(),

src/librustc/traits/mod.rs

@@ -17,7 +17,7 @@ pub use self::ObligationCauseCode::*;
 
 use hir::def_id::DefId;
 use middle::free_region::FreeRegionMap;
-use ty::subst;
+use ty::subst::Substs;
 use ty::{self, Ty, TyCtxt, TypeFoldable};
 use infer::InferCtxt;
 
@@ -272,7 +272,7 @@ pub enum Vtable<'tcx, N> {
 #[derive(Clone, PartialEq, Eq)]
 pub struct VtableImplData<'tcx, N> {
     pub impl_def_id: DefId,
-    pub substs: &'tcx subst::Substs<'tcx>,
+    pub substs: &'tcx Substs<'tcx>,
     pub nested: Vec<N>
 }
 

src/librustc/traits/object_safety.rs

@@ -166,25 +166,20 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     }
 
     fn trait_has_sized_self(self, trait_def_id: DefId) -> bool {
-        let trait_def = self.lookup_trait_def(trait_def_id);
-        let trait_predicates = self.lookup_predicates(trait_def_id);
-        self.generics_require_sized_self(&trait_def.generics, &trait_predicates)
+        self.generics_require_sized_self(trait_def_id)
     }
 
-    fn generics_require_sized_self(self,
-                                   generics: &ty::Generics<'gcx>,
-                                   predicates: &ty::GenericPredicates<'gcx>)
-                                   -> bool
-    {
+    fn generics_require_sized_self(self, def_id: DefId) -> bool {
         let sized_def_id = match self.lang_items.sized_trait() {
             Some(def_id) => def_id,
             None => { return false; /* No Sized trait, can't require it! */ }
         };
 
         // Search for a predicate like `Self : Sized` amongst the trait bounds.
-        let free_substs = self.construct_free_substs(generics,
+        let free_substs = self.construct_free_substs(def_id,
             self.region_maps.node_extent(ast::DUMMY_NODE_ID));
-        let predicates = predicates.instantiate(self, &free_substs).predicates;
+        let predicates = self.lookup_predicates(def_id);
+        let predicates = predicates.instantiate(self, free_substs).predicates;
         elaborate_predicates(self, predicates)
             .any(|predicate| {
                 match predicate {
@@ -214,7 +209,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     {
         // Any method that has a `Self : Sized` requisite is otherwise
         // exempt from the regulations.
-        if self.generics_require_sized_self(&method.generics, &method.predicates) {
+        if self.generics_require_sized_self(method.def_id) {
             return None;
         }
 
@@ -231,7 +226,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
                                  -> bool
     {
         // Any method that has a `Self : Sized` requisite can't be called.
-        if self.generics_require_sized_self(&method.generics, &method.predicates) {
+        if self.generics_require_sized_self(method.def_id) {
             return false;
         }
 

src/librustc/traits/select.rs

@@ -42,6 +42,7 @@ use traits;
 use ty::fast_reject;
 use ty::relate::TypeRelation;
 
+use rustc_data_structures::bitvec::BitVector;
 use rustc_data_structures::snapshot_vec::{SnapshotVecDelegate, SnapshotVec};
 use std::cell::RefCell;
 use std::fmt;
@@ -1935,7 +1936,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
 
             // for `PhantomData<T>`, we pass `T`
             ty::TyStruct(def, substs) if def.is_phantom_data() => {
-                substs.types.get_slice(TypeSpace).to_vec()
+                substs.types.as_full_slice().to_vec()
             }
 
             ty::TyStruct(def, substs) | ty::TyEnum(def, substs) => {
@@ -2584,30 +2585,33 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                 } else {
                     return Err(Unimplemented);
                 };
-                let mut ty_params = vec![];
+                let mut ty_params = BitVector::new(substs_a.types.len(TypeSpace));
+                let mut found = false;
                 for ty in field.walk() {
                     if let ty::TyParam(p) = ty.sty {
                         assert!(p.space == TypeSpace);
-                        let idx = p.idx as usize;
-                        if !ty_params.contains(&idx) {
-                            ty_params.push(idx);
-                        }
+                        ty_params.insert(p.idx as usize);
+                        found = true;
                     }
                 }
-                if ty_params.is_empty() {
+                if !found {
                     return Err(Unimplemented);
                 }
 
                 // Replace type parameters used in unsizing with
                 // TyError and ensure they do not affect any other fields.
                 // This could be checked after type collection for any struct
                 // with a potentially unsized trailing field.
-                let mut new_substs = substs_a.clone();
-                for &i in &ty_params {
-                    new_substs.types.get_mut_slice(TypeSpace)[i] = tcx.types.err;
-                }
+                let types = substs_a.types.map_enumerated(|(_, i, ty)| {
+                    if ty_params.contains(i) {
+                        tcx.types.err
+                    } else {
+                        ty
+                    }
+                });
+                let substs = Substs::new(tcx, types, substs_a.regions.clone());
                 for &ty in fields.split_last().unwrap().1 {
-                    if ty.subst(tcx, &new_substs).references_error() {
+                    if ty.subst(tcx, substs).references_error() {
                         return Err(Unimplemented);
                     }
                 }
@@ -2618,11 +2622,15 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
 
                 // Check that the source structure with the target's
                 // type parameters is a subtype of the target.
-                for &i in &ty_params {
-                    let param_b = *substs_b.types.get(TypeSpace, i);
-                    new_substs.types.get_mut_slice(TypeSpace)[i] = param_b;
-                }
-                let new_struct = tcx.mk_struct(def, tcx.mk_substs(new_substs));
+                let types = substs_a.types.map_enumerated(|(_, i, ty)| {
+                    if ty_params.contains(i) {
+                        *substs_b.types.get(TypeSpace, i)
+                    } else {
+                        ty
+                    }
+                });
+                let substs = Substs::new(tcx, types, substs_a.regions.clone());
+                let new_struct = tcx.mk_struct(def, substs);
                 let origin = TypeOrigin::Misc(obligation.cause.span);
                 let InferOk { obligations, .. } =
                     self.infcx.sub_types(false, origin, new_struct, target)
@@ -2691,12 +2699,11 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
             snapshot);
         let skol_obligation_trait_ref = skol_obligation.trait_ref;
 
-        let impl_substs = util::fresh_type_vars_for_impl(self.infcx,
-                                                         obligation.cause.span,
-                                                         impl_def_id);
+        let impl_substs = self.infcx.fresh_substs_for_item(obligation.cause.span,
+                                                           impl_def_id);
 
         let impl_trait_ref = impl_trait_ref.subst(self.tcx(),
-                                                  &impl_substs);
+                                                  impl_substs);
 
         let impl_trait_ref =
             project::normalize_with_depth(self,