Auto merge of #43559 - Nashenas88:nll-region-renumberer, r=arielb1

Non-lexical lifetimes region renumberer

Regenerates region variables for all regions in a cloned MIR in the nll mir pass. This is part of the work for #43234.

Author: bors

src/librustc/mir/visit.rs

@@ -753,6 +753,7 @@ macro_rules! make_mir_visitor {
 make_mir_visitor!(Visitor,);
 make_mir_visitor!(MutVisitor,mut);
 
+#[derive(Copy, Clone, Debug)]
 pub enum Lookup {
     Loc(Location),
     Src(SourceInfo),

src/librustc_mir/transform/nll.rs

@@ -8,26 +8,119 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use rustc::ty::TyCtxt;
-use rustc::mir::Mir;
-use rustc::mir::visit::MutVisitor;
+use rustc::ty::TypeFoldable;
+use rustc::ty::subst::{Kind, Substs};
+use rustc::ty::{Ty, TyCtxt, ClosureSubsts, RegionVid, RegionKind};
+use rustc::mir::{Mir, Location, Rvalue, BasicBlock, Statement, StatementKind};
+use rustc::mir::visit::{MutVisitor, Lookup};
 use rustc::mir::transform::{MirPass, MirSource};
+use rustc::infer::{self, InferCtxt};
+use syntax_pos::DUMMY_SP;
+use std::collections::HashMap;
 
 #[allow(dead_code)]
-struct NLLVisitor<'a, 'tcx: 'a> {
-    tcx: TyCtxt<'a, 'tcx, 'tcx>,
+struct NLLVisitor<'a, 'gcx: 'a + 'tcx, 'tcx: 'a> {
+    lookup_map: HashMap<RegionVid, Lookup>,
+    infcx: InferCtxt<'a, 'gcx, 'tcx>,
 }
 
-impl<'a, 'tcx> NLLVisitor<'a, 'tcx> {
-    pub fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Self {
+impl<'a, 'gcx, 'tcx> NLLVisitor<'a, 'gcx, 'tcx> {
+    pub fn new(infcx: InferCtxt<'a, 'gcx, 'tcx>) -> Self {
         NLLVisitor {
-            tcx: tcx
+            infcx: infcx,
+            lookup_map: HashMap::new(),
+        }
+    }
+
+    pub fn into_results(self) -> HashMap<RegionVid, Lookup> {
+        self.lookup_map
+    }
+
+    fn renumber_regions<T>(&self, value: &T) -> T where T: TypeFoldable<'tcx> {
+        self.infcx.tcx.fold_regions(value, &mut false, |_region, _depth| {
+            self.infcx.next_region_var(infer::MiscVariable(DUMMY_SP))
+        })
+    }
+
+    fn store_region(&mut self, region: &RegionKind, lookup: Lookup) {
+        if let RegionKind::ReVar(rid) = *region {
+            self.lookup_map.entry(rid).or_insert(lookup);
+        }
+    }
+
+    fn store_ty_regions(&mut self, ty: &Ty<'tcx>, lookup: Lookup) {
+        for region in ty.regions() {
+            self.store_region(region, lookup);
+        }
+    }
+
+    fn store_kind_regions(&mut self, kind: &'tcx Kind, lookup: Lookup) {
+        if let Some(ty) = kind.as_type() {
+            self.store_ty_regions(&ty, lookup);
+        } else if let Some(region) = kind.as_region() {
+            self.store_region(region, lookup);
         }
     }
 }
 
-impl<'a, 'tcx> MutVisitor<'tcx> for NLLVisitor<'a, 'tcx> {
-    // FIXME: Nashenas88: implement me!
+impl<'a, 'gcx, 'tcx> MutVisitor<'tcx> for NLLVisitor<'a, 'gcx, 'tcx> {
+    fn visit_ty(&mut self, ty: &mut Ty<'tcx>, lookup: Lookup) {
+        let old_ty = *ty;
+        *ty = self.renumber_regions(&old_ty);
+        self.store_ty_regions(ty, lookup);
+    }
+
+    fn visit_substs(&mut self, substs: &mut &'tcx Substs<'tcx>, location: Location) {
+        *substs = self.renumber_regions(&{*substs});
+        let lookup = Lookup::Loc(location);
+        for kind in *substs {
+            self.store_kind_regions(kind, lookup);
+        }
+    }
+
+    fn visit_rvalue(&mut self, rvalue: &mut Rvalue<'tcx>, location: Location) {
+        match *rvalue {
+            Rvalue::Ref(ref mut r, _, _) => {
+                let old_r = *r;
+                *r = self.renumber_regions(&old_r);
+                let lookup = Lookup::Loc(location);
+                self.store_region(r, lookup);
+            }
+            Rvalue::Use(..) |
+            Rvalue::Repeat(..) |
+            Rvalue::Len(..) |
+            Rvalue::Cast(..) |
+            Rvalue::BinaryOp(..) |
+            Rvalue::CheckedBinaryOp(..) |
+            Rvalue::UnaryOp(..) |
+            Rvalue::Discriminant(..) |
+            Rvalue::NullaryOp(..) |
+            Rvalue::Aggregate(..) => {
+                // These variants don't contain regions.
+            }
+        }
+        self.super_rvalue(rvalue, location);
+    }
+
+    fn visit_closure_substs(&mut self,
+                            substs: &mut ClosureSubsts<'tcx>,
+                            location: Location) {
+        *substs = self.renumber_regions(substs);
+        let lookup = Lookup::Loc(location);
+        for kind in substs.substs {
+            self.store_kind_regions(kind, lookup);
+        }
+    }
+
+    fn visit_statement(&mut self,
+                       block: BasicBlock,
+                       statement: &mut Statement<'tcx>,
+                       location: Location) {
+        if let StatementKind::EndRegion(_) = statement.kind {
+            statement.kind = StatementKind::Nop;
+        }
+        self.super_statement(block, statement, location);
+    }
 }
 
 // MIR Pass for non-lexical lifetimes
@@ -38,10 +131,16 @@ impl MirPass for NLL {
                           tcx: TyCtxt<'a, 'tcx, 'tcx>,
                           _: MirSource,
                           mir: &mut Mir<'tcx>) {
-        if tcx.sess.opts.debugging_opts.nll {
-            // Clone mir so we can mutate it without disturbing the rest
-            // of the compiler
-            NLLVisitor::new(tcx).visit_mir(&mut mir.clone());
+        if !tcx.sess.opts.debugging_opts.nll {
+            return;
         }
+
+        tcx.infer_ctxt().enter(|infcx| {
+            // Clone mir so we can mutate it without disturbing the rest of the compiler
+            let mut renumbered_mir = mir.clone();
+            let mut visitor = NLLVisitor::new(infcx);
+            visitor.visit_mir(&mut renumbered_mir);
+            let _results = visitor.into_results();
+        })
     }
 }