Auto merge of #44501 - nikomatsakis:issue-44137-non-query-data-in-tcx, r=eddyb

remove or encapsulate the remaining non-query data in tcx

I wound up removing the existing cache around inhabitedness since it didn't seem to be adding much value. I reworked const rvalue promotion, but not that much (i.e., I did not split the computation into bits, as @eddyb had tossed out as a suggestion). But it's now demand driven, at least.

cc @michaelwoerister -- see the `forbid_reads` change in last commit

r? @eddyb -- since the trickiest of this PR is the work on const rvalue promotion

cc #44137

Author: bors

CONTRIBUTING.md

@@ -360,8 +360,10 @@ git add path/to/submodule
 
 outside the submodule.
 
-It can also be more convenient during development to set `submodules = false`
-in the `config.toml` to prevent `x.py` from resetting to the original branch.
+In order to prepare your PR, you can run the build locally by doing
+`./x.py build src/tools/TOOL`. If you will be editing the sources
+there, you may wish to set `submodules = false` in the `config.toml`
+to prevent `x.py` from resetting to the original branch.
 
 ## Writing Documentation
 [writing-documentation]: #writing-documentation

src/librustc/dep_graph/dep_node.rs

@@ -554,6 +554,7 @@ define_dep_nodes!( <'tcx>
     [] LookupDeprecationEntry(DefId),
     [] ItemBodyNestedBodies(DefId),
     [] ConstIsRvaluePromotableToStatic(DefId),
+    [] RvaluePromotableMap(DefId),
     [] ImplParent(DefId),
     [] TraitOfItem(DefId),
     [] IsExportedSymbol(DefId),
@@ -609,6 +610,7 @@ define_dep_nodes!( <'tcx>
     [] PostorderCnums,
     [] HasCloneClosures(CrateNum),
     [] HasCopyClosures(CrateNum),
+    [] EraseRegionsTy { ty: Ty<'tcx> },
 
     [] Freevars(DefId),
     [] MaybeUnusedTraitImport(DefId),

src/librustc/lib.rs

@@ -60,7 +60,7 @@
 #![cfg_attr(stage0, feature(const_fn))]
 #![cfg_attr(not(stage0), feature(const_atomic_bool_new))]
 
-#![recursion_limit="256"]
+#![recursion_limit="512"]
 
 extern crate arena;
 #[macro_use] extern crate bitflags;

src/librustc/middle/expr_use_visitor.rs

@@ -27,10 +27,11 @@ use middle::region;
 use ty::{self, TyCtxt, adjustment};
 
 use hir::{self, PatKind};
-
+use std::rc::Rc;
 use syntax::ast;
 use syntax::ptr::P;
 use syntax_pos::Span;
+use util::nodemap::ItemLocalMap;
 
 ///////////////////////////////////////////////////////////////////////////
 // The Delegate trait
@@ -262,15 +263,30 @@ macro_rules! return_if_err {
 }
 
 impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx, 'tcx> {
+    /// Creates the ExprUseVisitor, configuring it with the various options provided:
+    ///
+    /// - `delegate` -- who receives the callbacks
+    /// - `param_env` --- parameter environment for trait lookups (esp. pertaining to `Copy`)
+    /// - `region_scope_tree` --- region scope tree for the code being analyzed
+    /// - `tables` --- typeck results for the code being analyzed
+    /// - `rvalue_promotable_map` --- if you care about rvalue promotion, then provide
+    ///   the map here (it can be computed with `tcx.rvalue_promotable_map(def_id)`).
+    ///   `None` means that rvalues will be given more conservative lifetimes.
+    ///
+    /// See also `with_infer`, which is used *during* typeck.
     pub fn new(delegate: &'a mut (Delegate<'tcx>+'a),
                tcx: TyCtxt<'a, 'tcx, 'tcx>,
                param_env: ty::ParamEnv<'tcx>,
                region_scope_tree: &'a region::ScopeTree,
-               tables: &'a ty::TypeckTables<'tcx>)
+               tables: &'a ty::TypeckTables<'tcx>,
+               rvalue_promotable_map: Option<Rc<ItemLocalMap<bool>>>)
                -> Self
     {
         ExprUseVisitor {
-            mc: mc::MemCategorizationContext::new(tcx, region_scope_tree, tables),
+            mc: mc::MemCategorizationContext::new(tcx,
+                                                  region_scope_tree,
+                                                  tables,
+                                                  rvalue_promotable_map),
             delegate,
             param_env,
         }

src/librustc/middle/mem_categorization.rs

@@ -86,6 +86,7 @@ use syntax_pos::Span;
 
 use std::fmt;
 use std::rc::Rc;
+use util::nodemap::ItemLocalMap;
 
 #[derive(Clone, PartialEq)]
 pub enum Categorization<'tcx> {
@@ -285,6 +286,7 @@ pub struct MemCategorizationContext<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
     pub tcx: TyCtxt<'a, 'gcx, 'tcx>,
     pub region_scope_tree: &'a region::ScopeTree,
     pub tables: &'a ty::TypeckTables<'tcx>,
+    rvalue_promotable_map: Option<Rc<ItemLocalMap<bool>>>,
     infcx: Option<&'a InferCtxt<'a, 'gcx, 'tcx>>,
 }
 
@@ -392,21 +394,46 @@ impl MutabilityCategory {
 impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx, 'tcx> {
     pub fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                region_scope_tree: &'a region::ScopeTree,
-               tables: &'a ty::TypeckTables<'tcx>)
+               tables: &'a ty::TypeckTables<'tcx>,
+               rvalue_promotable_map: Option<Rc<ItemLocalMap<bool>>>)
                -> MemCategorizationContext<'a, 'tcx, 'tcx> {
-        MemCategorizationContext { tcx, region_scope_tree, tables, infcx: None }
+        MemCategorizationContext {
+            tcx,
+            region_scope_tree,
+            tables,
+            rvalue_promotable_map,
+            infcx: None
+        }
     }
 }
 
 impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
+    /// Creates a `MemCategorizationContext` during type inference.
+    /// This is used during upvar analysis and a few other places.
+    /// Because the typeck tables are not yet complete, the results
+    /// from the analysis must be used with caution:
+    ///
+    /// - rvalue promotions are not known, so the lifetimes of
+    ///   temporaries may be overly conservative;
+    /// - similarly, as the results of upvar analysis are not yet
+    ///   known, the results around upvar accesses may be incorrect.
     pub fn with_infer(infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
                       region_scope_tree: &'a region::ScopeTree,
                       tables: &'a ty::TypeckTables<'tcx>)
                       -> MemCategorizationContext<'a, 'gcx, 'tcx> {
+        let tcx = infcx.tcx;
+
+        // Subtle: we can't do rvalue promotion analysis until the
+        // typeck phase is complete, which means that you can't trust
+        // the rvalue lifetimes that result, but that's ok, since we
+        // don't need to know those during type inference.
+        let rvalue_promotable_map = None;
+
         MemCategorizationContext {
-            tcx: infcx.tcx,
+            tcx,
             region_scope_tree,
             tables,
+            rvalue_promotable_map,
             infcx: Some(infcx),
         }
     }
@@ -869,8 +896,9 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
                            span: Span,
                            expr_ty: Ty<'tcx>)
                            -> cmt<'tcx> {
-        let promotable = self.tcx.rvalue_promotable_to_static.borrow().get(&id).cloned()
-                                   .unwrap_or(false);
+        let hir_id = self.tcx.hir.node_to_hir_id(id);
+        let promotable = self.rvalue_promotable_map.as_ref().map(|m| m[&hir_id.local_id])
+                                                            .unwrap_or(false);
 
         // Always promote `[T; 0]` (even when e.g. borrowed mutably).
         let promotable = match expr_ty.sty {
@@ -885,7 +913,7 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
         let re = if promotable {
             self.tcx.types.re_static
         } else {
-            self.temporary_scope(self.tcx.hir.node_to_hir_id(id).local_id)
+            self.temporary_scope(hir_id.local_id)
         };
         let ret = self.cat_rvalue(id, span, re, expr_ty);
         debug!("cat_rvalue_node ret {:?}", ret);

src/librustc/ty/context.rs

@@ -43,7 +43,6 @@ use ty::RegionKind;
 use ty::{TyVar, TyVid, IntVar, IntVid, FloatVar, FloatVid};
 use ty::TypeVariants::*;
 use ty::layout::{Layout, TargetDataLayout};
-use ty::inhabitedness::DefIdForest;
 use ty::maps;
 use ty::steal::Steal;
 use ty::BindingMode;
@@ -893,11 +892,6 @@ pub struct GlobalCtxt<'tcx> {
     // Internal cache for metadata decoding. No need to track deps on this.
     pub rcache: RefCell<FxHashMap<ty::CReaderCacheKey, Ty<'tcx>>>,
 
-    // FIXME dep tracking -- should be harmless enough
-    pub normalized_cache: RefCell<FxHashMap<Ty<'tcx>, Ty<'tcx>>>,
-
-    pub inhabitedness_cache: RefCell<FxHashMap<Ty<'tcx>, DefIdForest>>,
-
     /// Caches the results of trait selection. This cache is used
     /// for things that do not have to do with the parameters in scope.
     pub selection_cache: traits::SelectionCache<'tcx>,
@@ -907,9 +901,6 @@ pub struct GlobalCtxt<'tcx> {
     /// Merge this with `selection_cache`?
     pub evaluation_cache: traits::EvaluationCache<'tcx>,
 
-    /// Maps Expr NodeId's to `true` iff `&expr` can have 'static lifetime.
-    pub rvalue_promotable_to_static: RefCell<NodeMap<bool>>,
-
     /// The definite name of the current crate after taking into account
     /// attributes, commandline parameters, etc.
     pub crate_name: Symbol,
@@ -1178,11 +1169,8 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
             maps: maps::Maps::new(providers),
             mir_passes,
             rcache: RefCell::new(FxHashMap()),
-            normalized_cache: RefCell::new(FxHashMap()),
-            inhabitedness_cache: RefCell::new(FxHashMap()),
             selection_cache: traits::SelectionCache::new(),
             evaluation_cache: traits::EvaluationCache::new(),
-            rvalue_promotable_to_static: RefCell::new(NodeMap()),
             crate_name: Symbol::intern(crate_name),
             data_layout,
             layout_interner: RefCell::new(FxHashSet()),

src/librustc/ty/erase_regions.rs

@@ -0,0 +1,79 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use ty::{self, Ty, TyCtxt};
+use ty::fold::{TypeFolder, TypeFoldable};
+
+pub(super) fn provide(providers: &mut ty::maps::Providers) {
+    *providers = ty::maps::Providers {
+        erase_regions_ty,
+        ..*providers
+    };
+}
+
+fn erase_regions_ty<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, ty: Ty<'tcx>) -> Ty<'tcx> {
+    // NB: use `super_fold_with` here. If we used `fold_with`, it
+    // could invoke the `erase_regions_ty` query recursively.
+    ty.super_fold_with(&mut RegionEraserVisitor { tcx })
+}
+
+impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
+    /// Returns an equivalent value with all free regions removed (note
+    /// that late-bound regions remain, because they are important for
+    /// subtyping, but they are anonymized and normalized as well)..
+    pub fn erase_regions<T>(self, value: &T) -> T
+        where T : TypeFoldable<'tcx>
+    {
+        let value1 = value.fold_with(&mut RegionEraserVisitor { tcx: self });
+        debug!("erase_regions({:?}) = {:?}", value, value1);
+        value1
+    }
+}
+
+struct RegionEraserVisitor<'a, 'gcx: 'tcx, 'tcx: 'a> {
+    tcx: TyCtxt<'a, 'gcx, 'tcx>,
+}
+
+impl<'a, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for RegionEraserVisitor<'a, 'gcx, 'tcx> {
+    fn tcx<'b>(&'b self) -> TyCtxt<'b, 'gcx, 'tcx> {
+        self.tcx
+    }
+
+    fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
+        if let Some(ty_lifted) = self.tcx.lift_to_global(&ty) {
+            self.tcx.erase_regions_ty(ty_lifted)
+        } else {
+            ty.super_fold_with(self)
+        }
+    }
+
+    fn fold_binder<T>(&mut self, t: &ty::Binder<T>) -> ty::Binder<T>
+        where T : TypeFoldable<'tcx>
+    {
+        let u = self.tcx.anonymize_late_bound_regions(t);
+        u.super_fold_with(self)
+    }
+
+    fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
+        // because late-bound regions affect subtyping, we can't
+        // erase the bound/free distinction, but we can replace
+        // all free regions with 'erased.
+        //
+        // Note that we *CAN* replace early-bound regions -- the
+        // type system never "sees" those, they get substituted
+        // away. In trans, they will always be erased to 'erased
+        // whenever a substitution occurs.
+        match *r {
+            ty::ReLateBound(..) => r,
+            _ => self.tcx.types.re_erased
+        }
+    }
+}
+

src/librustc/ty/fold.rs

@@ -444,67 +444,6 @@ impl<'a, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for RegionReplacer<'a, 'gcx, 'tcx> {
     }
 }
 
-///////////////////////////////////////////////////////////////////////////
-// Region eraser
-
-impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
-    /// Returns an equivalent value with all free regions removed (note
-    /// that late-bound regions remain, because they are important for
-    /// subtyping, but they are anonymized and normalized as well)..
-    pub fn erase_regions<T>(self, value: &T) -> T
-        where T : TypeFoldable<'tcx>
-    {
-        let value1 = value.fold_with(&mut RegionEraser(self));
-        debug!("erase_regions({:?}) = {:?}",
-               value, value1);
-        return value1;
-
-        struct RegionEraser<'a, 'gcx: 'a+'tcx, 'tcx: 'a>(TyCtxt<'a, 'gcx, 'tcx>);
-
-        impl<'a, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for RegionEraser<'a, 'gcx, 'tcx> {
-            fn tcx<'b>(&'b self) -> TyCtxt<'b, 'gcx, 'tcx> { self.0 }
-
-            fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
-                if let Some(u) = self.tcx().normalized_cache.borrow().get(&ty).cloned() {
-                    return u;
-                }
-
-                // FIXME(eddyb) should local contexts have a cache too?
-                if let Some(ty_lifted) = self.tcx().lift_to_global(&ty) {
-                    let tcx = self.tcx().global_tcx();
-                    let t_norm = ty_lifted.super_fold_with(&mut RegionEraser(tcx));
-                    tcx.normalized_cache.borrow_mut().insert(ty_lifted, t_norm);
-                    t_norm
-                } else {
-                    ty.super_fold_with(self)
-                }
-            }
-
-            fn fold_binder<T>(&mut self, t: &ty::Binder<T>) -> ty::Binder<T>
-                where T : TypeFoldable<'tcx>
-            {
-                let u = self.tcx().anonymize_late_bound_regions(t);
-                u.super_fold_with(self)
-            }
-
-            fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
-                // because late-bound regions affect subtyping, we can't
-                // erase the bound/free distinction, but we can replace
-                // all free regions with 'erased.
-                //
-                // Note that we *CAN* replace early-bound regions -- the
-                // type system never "sees" those, they get substituted
-                // away. In trans, they will always be erased to 'erased
-                // whenever a substitution occurs.
-                match *r {
-                    ty::ReLateBound(..) => r,
-                    _ => self.tcx().types.re_erased
-                }
-            }
-        }
-    }
-}
-
 ///////////////////////////////////////////////////////////////////////////
 // Region shifter
 //