New scoping rules for safe destruction

src/compiletest/compiletest.rs

@@ -116,7 +116,10 @@ pub fn parse_config(args: Vec<String> ) -> Config {
     }
 
     fn opt_path(m: &getopts::Matches, nm: &str) -> Path {
-        Path::new(m.opt_str(nm).unwrap())
+        match m.opt_str(nm) {
+            Some(s) => Path::new(s),
+            None => panic!("no option (=path) found for {}", nm),
+        }
     }
 
     let filter = if !matches.free.is_empty() {

src/libregex/vm.rs

@@ -120,8 +120,10 @@ impl<'r, 't> Nfa<'r, 't> {
         };
         let mut matched = false;
         let ninsts = self.prog.insts.len();
-        let mut clist = &mut Threads::new(self.which, ninsts, ncaps);
-        let mut nlist = &mut Threads::new(self.which, ninsts, ncaps);
+        let mut cthread = Threads::new(self.which, ninsts, ncaps);
+        let mut nthread = Threads::new(self.which, ninsts, ncaps);
+        let mut clist = &mut cthread;
+        let mut nlist = &mut nthread;
 
         let mut groups: Vec<_> = repeat(None).take(ncaps * 2).collect();
 

src/librustc/metadata/tydecode.rs

@@ -390,6 +390,18 @@ fn parse_scope(st: &mut PState) -> region::CodeExtent {
             let node_id = parse_uint(st) as ast::NodeId;
             region::CodeExtent::Misc(node_id)
         }
+        'D' => {
+            let node_id = parse_uint(st) as ast::NodeId;
+            region::CodeExtent::DestructionScope(node_id)
+        }
+        'B' => {
+            let node_id = parse_uint(st) as ast::NodeId;
+            let first_stmt_index = parse_uint(st);
+            let block_remainder = region::BlockRemainder {
+                block: node_id, first_statement_index: first_stmt_index,
+            };
+            region::CodeExtent::Remainder(block_remainder)
+        }
         _ => panic!("parse_scope: bad input")
     }
 }

src/librustc/metadata/tyencode.rs

@@ -276,7 +276,10 @@ pub fn enc_region(w: &mut SeekableMemWriter, cx: &ctxt, r: ty::Region) {
 
 fn enc_scope(w: &mut SeekableMemWriter, _cx: &ctxt, scope: region::CodeExtent) {
     match scope {
-        region::CodeExtent::Misc(node_id) => mywrite!(w, "M{}", node_id)
+        region::CodeExtent::Misc(node_id) => mywrite!(w, "M{}", node_id),
+        region::CodeExtent::Remainder(region::BlockRemainder {
+            block: b, first_statement_index: i }) => mywrite!(w, "B{}{}", b, i),
+        region::CodeExtent::DestructionScope(node_id) => mywrite!(w, "D{}", node_id),
     }
 }
 

src/librustc/middle/infer/error_reporting.rs

@@ -242,7 +242,7 @@ impl<'a, 'tcx> ErrorReporting<'tcx> for InferCtxt<'a, 'tcx> {
                     }
                 }
                 SubSupConflict(var_origin, _, sub_r, _, sup_r) => {
-                    debug!("processing SubSupConflict");
+                    debug!("processing SubSupConflict sub: {:?} sup: {:?}", sub_r, sup_r);
                     match free_regions_from_same_fn(self.tcx, sub_r, sup_r) {
                         Some(ref same_frs) => {
                             var_origins.push(var_origin);
@@ -721,6 +721,22 @@ impl<'a, 'tcx> ErrorReporting<'tcx> for InferCtxt<'a, 'tcx> {
                     sup,
                     "");
             }
+            infer::SafeDestructor(span) => {
+                self.tcx.sess.span_err(
+                    span,
+                    "unsafe use of destructor: destructor might be called \
+                     while references are dead");
+                note_and_explain_region(
+                    self.tcx,
+                    "superregion: ",
+                    sup,
+                    "");
+                note_and_explain_region(
+                    self.tcx,
+                    "subregion: ",
+                    sub,
+                    "");
+            }
             infer::BindingTypeIsNotValidAtDecl(span) => {
                 self.tcx.sess.span_err(
                     span,
@@ -818,6 +834,8 @@ impl<'a, 'tcx> ErrorReporting<'tcx> for InferCtxt<'a, 'tcx> {
         let scope_id = same_regions[0].scope_id;
         let parent = self.tcx.map.get_parent(scope_id);
         let parent_node = self.tcx.map.find(parent);
+        let taken = lifetimes_in_scope(self.tcx, scope_id);
+        let life_giver = LifeGiver::with_taken(&taken[]);
         let node_inner = match parent_node {
             Some(ref node) => match *node {
                 ast_map::NodeItem(ref item) => {
@@ -860,8 +878,6 @@ impl<'a, 'tcx> ErrorReporting<'tcx> for InferCtxt<'a, 'tcx> {
         };
         let (fn_decl, generics, unsafety, ident, expl_self, span)
                                     = node_inner.expect("expect item fn");
-        let taken = lifetimes_in_scope(self.tcx, scope_id);
-        let life_giver = LifeGiver::with_taken(&taken[]);
         let rebuilder = Rebuilder::new(self.tcx, fn_decl, expl_self,
                                        generics, same_regions, &life_giver);
         let (fn_decl, expl_self, generics) = rebuilder.rebuild();
@@ -1641,6 +1657,12 @@ impl<'a, 'tcx> ErrorReportingHelpers<'tcx> for InferCtxt<'a, 'tcx> {
                     &format!("...so that the declared lifetime parameter bounds \
                                 are satisfied")[]);
             }
+            infer::SafeDestructor(span) => {
+                self.tcx.sess.span_note(
+                    span,
+                    "...so that references are valid when the destructor \
+                     runs")
+            }
         }
     }
 }

src/librustc/middle/infer/mod.rs

@@ -222,6 +222,9 @@ pub enum SubregionOrigin<'tcx> {
 
     // An auto-borrow that does not enclose the expr where it occurs
     AutoBorrow(Span),
+
+    // Region constraint arriving from destructor safety
+    SafeDestructor(Span),
 }
 
 /// Times when we replace late-bound regions with variables:
@@ -1217,6 +1220,7 @@ impl<'tcx> SubregionOrigin<'tcx> {
             CallReturn(a) => a,
             AddrOf(a) => a,
             AutoBorrow(a) => a,
+            SafeDestructor(a) => a,
         }
     }
 }
@@ -1279,6 +1283,7 @@ impl<'tcx> Repr<'tcx> for SubregionOrigin<'tcx> {
             CallReturn(a) => format!("CallReturn({})", a.repr(tcx)),
             AddrOf(a) => format!("AddrOf({})", a.repr(tcx)),
             AutoBorrow(a) => format!("AutoBorrow({})", a.repr(tcx)),
+            SafeDestructor(a) => format!("SafeDestructor({})", a.repr(tcx)),
         }
     }
 }

src/librustc/middle/infer/region_inference/graphviz.rs

@@ -19,12 +19,14 @@
 use graphviz as dot;
 
 use middle::ty;
+use middle::region::CodeExtent;
 use super::Constraint;
 use middle::infer::SubregionOrigin;
 use middle::infer::region_inference::RegionVarBindings;
 use util::nodemap::{FnvHashMap, FnvHashSet};
 use util::ppaux::Repr;
 
+use std::borrow::Cow;
 use std::collections::hash_map::Entry::Vacant;
 use std::io::{self, File};
 use std::os;
@@ -120,13 +122,18 @@ struct ConstraintGraph<'a, 'tcx: 'a> {
     node_ids: FnvHashMap<Node, uint>,
 }
 
-#[derive(Clone, Hash, PartialEq, Eq, Show)]
+#[derive(Clone, Hash, PartialEq, Eq, Show, Copy)]
 enum Node {
     RegionVid(ty::RegionVid),
     Region(ty::Region),
 }
 
-type Edge = Constraint;
+// type Edge = Constraint;
+#[derive(Clone, PartialEq, Eq, Show, Copy)]
+enum Edge {
+    Constraint(Constraint),
+    EnclScope(CodeExtent, CodeExtent),
+}
 
 impl<'a, 'tcx> ConstraintGraph<'a, 'tcx> {
     fn new(tcx: &'a ty::ctxt<'tcx>,
@@ -146,6 +153,11 @@ impl<'a, 'tcx> ConstraintGraph<'a, 'tcx> {
                 add_node(n1);
                 add_node(n2);
             }
+
+            tcx.region_maps.each_encl_scope(|&mut: sub, sup| {
+                add_node(Node::Region(ty::ReScope(*sub)));
+                add_node(Node::Region(ty::ReScope(*sup)));
+            });
         }
 
         ConstraintGraph { tcx: tcx,
@@ -160,7 +172,17 @@ impl<'a, 'tcx> dot::Labeller<'a, Node, Edge> for ConstraintGraph<'a, 'tcx> {
         dot::Id::new(self.graph_name.as_slice()).unwrap()
     }
     fn node_id(&self, n: &Node) -> dot::Id {
-        dot::Id::new(format!("node_{}", self.node_ids.get(n).unwrap())).unwrap()
+        let node_id = match self.node_ids.get(n) {
+            Some(node_id) => node_id,
+            None => panic!("no node_id found for node: {:?}", n),
+        };
+        let name = |&:| format!("node_{}", node_id);
+        match dot::Id::new(name()) {
+            Ok(id) => id,
+            Err(()) => {
+                panic!("failed to create graphviz node identified by {}", name());
+            }
+        }
     }
     fn node_label(&self, n: &Node) -> dot::LabelText {
         match *n {
@@ -171,7 +193,12 @@ impl<'a, 'tcx> dot::Labeller<'a, Node, Edge> for ConstraintGraph<'a, 'tcx> {
         }
     }
     fn edge_label(&self, e: &Edge) -> dot::LabelText {
-        dot::LabelText::label(format!("{}", self.map.get(e).unwrap().repr(self.tcx)))
+        match *e {
+            Edge::Constraint(ref c) =>
+                dot::LabelText::label(format!("{}", self.map.get(c).unwrap().repr(self.tcx))),
+            Edge::EnclScope(..) =>
+                dot::LabelText::label(format!("(enclosed)")),
+        }
     }
 }
 
@@ -186,28 +213,40 @@ fn constraint_to_nodes(c: &Constraint) -> (Node, Node) {
     }
 }
 
+fn edge_to_nodes(e: &Edge) -> (Node, Node) {
+    match *e {
+        Edge::Constraint(ref c) => constraint_to_nodes(c),
+        Edge::EnclScope(sub, sup) => {
+            (Node::Region(ty::ReScope(sub)), Node::Region(ty::ReScope(sup)))
+        }
+    }
+}
+
 impl<'a, 'tcx> dot::GraphWalk<'a, Node, Edge> for ConstraintGraph<'a, 'tcx> {
     fn nodes(&self) -> dot::Nodes<Node> {
         let mut set = FnvHashSet::new();
-        for constraint in self.map.keys() {
-            let (n1, n2) = constraint_to_nodes(constraint);
-            set.insert(n1);
-            set.insert(n2);
+        for node in self.node_ids.keys() {
+            set.insert(*node);
         }
         debug!("constraint graph has {} nodes", set.len());
         set.into_iter().collect()
     }
     fn edges(&self) -> dot::Edges<Edge> {
         debug!("constraint graph has {} edges", self.map.len());
-        self.map.keys().map(|e|*e).collect()
+        let mut v : Vec<_> = self.map.keys().map(|e| Edge::Constraint(*e)).collect();
+        self.tcx.region_maps.each_encl_scope(|&mut: sub, sup| {
+            v.push(Edge::EnclScope(*sub, *sup))
+        });
+        debug!("region graph has {} edges", v.len());
+        Cow::Owned(v)
     }
     fn source(&self, edge: &Edge) -> Node {
-        let (n1, _) = constraint_to_nodes(edge);
+        let (n1, _) = edge_to_nodes(edge);
         debug!("edge {:?} has source {:?}", edge, n1);
         n1
     }
     fn target(&self, edge: &Edge) -> Node {
-        let (_, n2) = constraint_to_nodes(edge);
+        let (_, n2) = edge_to_nodes(edge);
         debug!("edge {:?} has target {:?}", edge, n2);
         n2
     }

src/librustc/middle/infer/region_inference/mod.rs

@@ -1398,6 +1398,8 @@ impl<'a, 'tcx> RegionVarBindings<'a, 'tcx> {
             for upper_bound in upper_bounds.iter() {
                 if !self.is_subregion_of(lower_bound.region,
                                          upper_bound.region) {
+                    debug!("pushing SubSupConflict sub: {:?} sup: {:?}",
+                           lower_bound.region, upper_bound.region);
                     errors.push(SubSupConflict(
                         (*self.var_origins.borrow())[node_idx.index as uint].clone(),
                         lower_bound.origin.clone(),

src/librustc/middle/liveness.rs

@@ -1535,7 +1535,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
         let fn_ret =
             ty::liberate_late_bound_regions(
                 self.ir.tcx,
-                CodeExtent::from_node_id(body.id),
+                CodeExtent::DestructionScope(body.id),
                 &self.fn_ret(id));
 
         match fn_ret {

src/librustc/middle/mem_categorization.rs

@@ -690,7 +690,10 @@ impl<'t,'tcx,TYPER:Typer<'tcx>> MemCategorizationContext<'t,TYPER> {
 
             // Region of environment pointer
             let env_region = ty::ReFree(ty::FreeRegion {
-                scope: region::CodeExtent::from_node_id(fn_body_id),
+                // The environment of a closure is guaranteed to
+                // outlive any bindings introduced in the body of the
+                // closure itself.
+                scope: region::CodeExtent::DestructionScope(fn_body_id),
                 bound_region: ty::BrEnv
             });