Auto merge of #33622 - arielb1:elaborate-drops, r=nikomatsakis

[MIR] non-zeroing drop

This enables non-zeroing drop through stack flags for MIR.

Fixes #30380.
Fixes #5016.

src/librustc/infer/mod.rs

@@ -624,6 +624,24 @@ impl<'a, 'tcx> TyCtxt<'a, 'tcx, 'tcx> {
             value.trans_normalize(&infcx)
         })
     }
+
+    pub fn normalize_associated_type_in_env<T>(
+        self, value: &T, env: &'a ty::ParameterEnvironment<'tcx>
+    ) -> T
+        where T: TransNormalize<'tcx>
+    {
+        debug!("normalize_associated_type_in_env(t={:?})", value);
+
+        let value = self.erase_regions(value);
+
+        if !value.has_projection_types() {
+            return value;
+        }
+
+        self.infer_ctxt(None, Some(env.clone()), ProjectionMode::Any).enter(|infcx| {
+            value.trans_normalize(&infcx)
+       })
+    }
 }
 
 impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {

src/librustc/middle/cstore.rs

@@ -163,6 +163,7 @@ pub trait CrateStore<'tcx> {
                      -> ty::TypeScheme<'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)
@@ -345,6 +346,7 @@ impl<'tcx> CrateStore<'tcx> for DummyCrateStore {
         bug!("visible_parent_map")
     }
     fn item_name(&self, def: DefId) -> ast::Name { bug!("item_name") }
+    fn opt_item_name(&self, def: DefId) -> Option<ast::Name> { bug!("opt_item_name") }
     fn item_predicates<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
                            -> ty::GenericPredicates<'tcx> { bug!("item_predicates") }
     fn item_super_predicates<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)

src/librustc/mir/repr.rs

@@ -330,11 +330,19 @@ pub enum TerminatorKind<'tcx> {
 
     /// Drop the Lvalue
     Drop {
-        value: Lvalue<'tcx>,
+        location: Lvalue<'tcx>,
         target: BasicBlock,
         unwind: Option<BasicBlock>
     },
 
+    /// Drop the Lvalue and assign the new value over it
+    DropAndReplace {
+        location: Lvalue<'tcx>,
+        value: Operand<'tcx>,
+        target: BasicBlock,
+        unwind: Option<BasicBlock>,
+    },
+
     /// Block ends with a call of a converging function
     Call {
         /// The function that’s being called
@@ -373,8 +381,14 @@ impl<'tcx> TerminatorKind<'tcx> {
                 slice::ref_slice(t).into_cow(),
             Call { destination: None, cleanup: Some(ref c), .. } => slice::ref_slice(c).into_cow(),
             Call { destination: None, cleanup: None, .. } => (&[]).into_cow(),
-            Drop { target, unwind: Some(unwind), .. } => vec![target, unwind].into_cow(),
-            Drop { ref target, .. } => slice::ref_slice(target).into_cow(),
+            DropAndReplace { target, unwind: Some(unwind), .. } |
+            Drop { target, unwind: Some(unwind), .. } => {
+                vec![target, unwind].into_cow()
+            }
+            DropAndReplace { ref target, unwind: None, .. } |
+            Drop { ref target, unwind: None, .. } => {
+                slice::ref_slice(target).into_cow()
+            }
         }
     }
 
@@ -393,8 +407,12 @@ impl<'tcx> TerminatorKind<'tcx> {
             Call { destination: Some((_, ref mut t)), cleanup: None, .. } => vec![t],
             Call { destination: None, cleanup: Some(ref mut c), .. } => vec![c],
             Call { destination: None, cleanup: None, .. } => vec![],
+            DropAndReplace { ref mut target, unwind: Some(ref mut unwind), .. } |
             Drop { ref mut target, unwind: Some(ref mut unwind), .. } => vec![target, unwind],
-            Drop { ref mut target, .. } => vec![target]
+            DropAndReplace { ref mut target, unwind: None, .. } |
+            Drop { ref mut target, unwind: None, .. } => {
+                vec![target]
+            }
         }
     }
 }
@@ -461,7 +479,9 @@ impl<'tcx> TerminatorKind<'tcx> {
             SwitchInt { discr: ref lv, .. } => write!(fmt, "switchInt({:?})", lv),
             Return => write!(fmt, "return"),
             Resume => write!(fmt, "resume"),
-            Drop { ref value, .. } => write!(fmt, "drop({:?})", value),
+            Drop { ref location, .. } => write!(fmt, "drop({:?})", location),
+            DropAndReplace { ref location, ref value, .. } =>
+                write!(fmt, "replace({:?} <- {:?})", location, value),
             Call { ref func, ref args, ref destination, .. } => {
                 if let Some((ref destination, _)) = *destination {
                     write!(fmt, "{:?} = ", destination)?;
@@ -506,8 +526,12 @@ impl<'tcx> TerminatorKind<'tcx> {
             Call { destination: Some(_), cleanup: None, .. } => vec!["return".into_cow()],
             Call { destination: None, cleanup: Some(_), .. } => vec!["unwind".into_cow()],
             Call { destination: None, cleanup: None, .. } => vec![],
+            DropAndReplace { unwind: None, .. } |
             Drop { unwind: None, .. } => vec!["return".into_cow()],
-            Drop { .. } => vec!["return".into_cow(), "unwind".into_cow()],
+            DropAndReplace { unwind: Some(_), .. } |
+            Drop { unwind: Some(_), .. } => {
+                vec!["return".into_cow(), "unwind".into_cow()]
+            }
         }
     }
 }
@@ -918,7 +942,7 @@ impl<'tcx> Debug for Rvalue<'tcx> {
                         ppaux::parameterized(fmt, substs, variant_def.did,
                                              ppaux::Ns::Value, &[],
                                              |tcx| {
-                            tcx.lookup_item_type(variant_def.did).generics
+                            Some(tcx.lookup_item_type(variant_def.did).generics)
                         })?;
 
                         match variant_def.kind() {
@@ -1010,8 +1034,9 @@ 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| tcx.lookup_item_type(def_id).generics)
+                ppaux::parameterized(
+                    fmt, substs, def_id, ppaux::Ns::Value, &[],
+                    |tcx| Some(tcx.lookup_item_type(def_id).generics))
             }
             Value { ref value } => {
                 write!(fmt, "const ")?;

src/librustc/mir/visit.rs

@@ -394,10 +394,20 @@ macro_rules! make_mir_visitor {
                     TerminatorKind::Return => {
                     }
 
-                    TerminatorKind::Drop { ref $($mutability)* value,
+                    TerminatorKind::Drop { ref $($mutability)* location,
                                            target,
                                            unwind } => {
-                        self.visit_lvalue(value, LvalueContext::Drop);
+                        self.visit_lvalue(location, LvalueContext::Drop);
+                        self.visit_branch(block, target);
+                        unwind.map(|t| self.visit_branch(block, t));
+                    }
+
+                    TerminatorKind::DropAndReplace { ref $($mutability)* location,
+                                                     ref $($mutability)* value,
+                                                     target,
+                                                     unwind } => {
+                        self.visit_lvalue(location, LvalueContext::Drop);
+                        self.visit_operand(value);
                         self.visit_branch(block, target);
                         unwind.map(|t| self.visit_branch(block, t));
                     }

src/librustc/ty/item_path.rs

@@ -13,6 +13,7 @@ use middle::cstore::LOCAL_CRATE;
 use hir::def_id::{DefId, CRATE_DEF_INDEX};
 use ty::{self, Ty, TyCtxt};
 use syntax::ast;
+use syntax::parse::token;
 
 use std::cell::Cell;
 
@@ -138,7 +139,8 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
                 }
             }
 
-            cur_path.push(self.sess.cstore.item_name(cur_def));
+            cur_path.push(self.sess.cstore.opt_item_name(cur_def).unwrap_or_else(||
+                token::intern("<unnamed>")));
             match visible_parent_map.get(&cur_def) {
                 Some(&def) => cur_def = def,
                 None => return false,

src/librustc/ty/mod.rs

@@ -2503,6 +2503,18 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
             || self.sess.cstore.item_type(self.global_tcx(), did))
     }
 
+    pub fn opt_lookup_item_type(self, did: DefId) -> Option<TypeScheme<'gcx>> {
+        if let Some(scheme) = self.tcache.borrow_mut().get(&did) {
+            return Some(scheme.clone());
+        }
+
+        if did.krate == LOCAL_CRATE {
+            None
+        } else {
+            Some(self.sess.cstore.item_type(self.global_tcx(), did))
+        }
+    }
+
     /// Given the did of a trait, returns its canonical trait ref.
     pub fn lookup_trait_def(self, did: DefId) -> &'gcx TraitDef<'gcx> {
         lookup_locally_or_in_crate_store(

src/librustc/util/ppaux.rs

@@ -69,15 +69,12 @@ pub enum Ns {
     Value
 }
 
-fn number_of_supplied_defaults<'a, 'gcx, 'tcx, GG>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
-                                                   substs: &subst::Substs,
-                                                   space: subst::ParamSpace,
-                                                   get_generics: GG)
-                                                   -> usize
-    where GG: FnOnce(TyCtxt<'a, 'gcx, 'tcx>) -> ty::Generics<'tcx>
+fn number_of_supplied_defaults<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
+                                               substs: &subst::Substs,
+                                               space: subst::ParamSpace,
+                                               generics: ty::Generics<'tcx>)
+                                               -> usize
 {
-    let generics = get_generics(tcx);
-
     let has_self = substs.self_ty().is_some();
     let ty_params = generics.types.get_slice(space);
     let tps = substs.types.get_slice(space);
@@ -115,7 +112,8 @@ pub fn parameterized<GG>(f: &mut fmt::Formatter,
                          projections: &[ty::ProjectionPredicate],
                          get_generics: GG)
                          -> fmt::Result
-    where GG: for<'a, 'gcx, 'tcx> FnOnce(TyCtxt<'a, 'gcx, 'tcx>) -> ty::Generics<'tcx>
+    where GG: for<'a, 'gcx, 'tcx> FnOnce(TyCtxt<'a, 'gcx, 'tcx>)
+                                         -> Option<ty::Generics<'tcx>>
 {
     if let (Ns::Value, Some(self_ty)) = (ns, substs.self_ty()) {
         write!(f, "<{} as ", self_ty)?;
@@ -176,13 +174,12 @@ pub fn parameterized<GG>(f: &mut fmt::Formatter,
     let num_supplied_defaults = if verbose {
         0
     } else {
-        // It is important to execute this conditionally, only if -Z
-        // verbose is false. Otherwise, debug logs can sometimes cause
-        // ICEs trying to fetch the generics early in the pipeline. This
-        // is kind of a hacky workaround in that -Z verbose is required to
-        // avoid those ICEs.
         ty::tls::with(|tcx| {
-            number_of_supplied_defaults(tcx, substs, subst::TypeSpace, get_generics)
+            if let Some(generics) = get_generics(tcx) {
+                number_of_supplied_defaults(tcx, substs, subst::TypeSpace, generics)
+            } else {
+                0
+            }
         })
     };
 
@@ -312,7 +309,7 @@ impl<'tcx> fmt::Display for TraitAndProjections<'tcx> {
                       trait_ref.def_id,
                       Ns::Type,
                       projection_bounds,
-                      |tcx| tcx.lookup_trait_def(trait_ref.def_id).generics.clone())
+                      |tcx| Some(tcx.lookup_trait_def(trait_ref.def_id).generics.clone()))
     }
 }
 
@@ -814,7 +811,7 @@ impl fmt::Display for ty::Binder<ty::OutlivesPredicate<ty::Region, ty::Region>>
 impl<'tcx> fmt::Display for ty::TraitRef<'tcx> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         parameterized(f, self.substs, self.def_id, Ns::Type, &[],
-                      |tcx| tcx.lookup_trait_def(self.def_id).generics.clone())
+                      |tcx| Some(tcx.lookup_trait_def(self.def_id).generics.clone()))
     }
 }
 
@@ -866,8 +863,9 @@ impl<'tcx> fmt::Display for ty::TypeVariants<'tcx> {
                 }
 
                 write!(f, "{} {{", bare_fn.sig.0)?;
-                parameterized(f, substs, def_id, Ns::Value, &[],
-                              |tcx| tcx.lookup_item_type(def_id).generics)?;
+                parameterized(
+                    f, substs, def_id, Ns::Value, &[],
+                    |tcx| tcx.opt_lookup_item_type(def_id).map(|t| t.generics))?;
                 write!(f, "}}")
             }
             TyFnPtr(ref bare_fn) => {
@@ -890,8 +888,12 @@ impl<'tcx> fmt::Display for ty::TypeVariants<'tcx> {
                           !tcx.tcache.borrow().contains_key(&def.did) {
                         write!(f, "{}<..>", tcx.item_path_str(def.did))
                     } else {
-                        parameterized(f, substs, def.did, Ns::Type, &[],
-                                      |tcx| tcx.lookup_item_type(def.did).generics)
+                        parameterized(
+                            f, substs, def.did, Ns::Type, &[],
+                            |tcx| {
+                                tcx.opt_lookup_item_type(def.did).
+                                    map(|t| t.generics)
+                            })
                     }
                 })
             }

src/librustc_borrowck/borrowck/mir/dataflow/mod.rs

@@ -200,6 +200,12 @@ impl<'a, 'tcx: 'a, O> DataflowAnalysis<'a, 'tcx, O>
 
 pub struct DataflowResults<O>(DataflowState<O>) where O: BitDenotation;
 
+impl<O: BitDenotation> DataflowResults<O> {
+    pub fn sets(&self) -> &AllSets<O::Idx> {
+        &self.0.sets
+    }
+}
+
 // FIXME: This type shouldn't be public, but the graphviz::MirWithFlowState trait
 // references it in a method signature. Look into using `pub(crate)` to address this.
 pub struct DataflowState<O: BitDenotation>
@@ -444,10 +450,17 @@ impl<'a, 'tcx: 'a, D> DataflowAnalysis<'a, 'tcx, D>
             repr::TerminatorKind::Return |
             repr::TerminatorKind::Resume => {}
             repr::TerminatorKind::Goto { ref target } |
-            repr::TerminatorKind::Drop { ref target, value: _, unwind: None } => {
+            repr::TerminatorKind::Drop { ref target, location: _, unwind: None } |
+
+            repr::TerminatorKind::DropAndReplace {
+                ref target, value: _, location: _, unwind: None
+            } => {
                 self.propagate_bits_into_entry_set_for(in_out, changed, target);
             }
-            repr::TerminatorKind::Drop { ref target, value: _, unwind: Some(ref unwind) } => {
+            repr::TerminatorKind::Drop { ref target, location: _, unwind: Some(ref unwind) } |
+            repr::TerminatorKind::DropAndReplace {
+                ref target, value: _, location: _, unwind: Some(ref unwind)
+            } => {
                 self.propagate_bits_into_entry_set_for(in_out, changed, target);
                 self.propagate_bits_into_entry_set_for(in_out, changed, unwind);
             }