collect unused unsafe code

FIXME: de-uglify

src/librustc/dep_graph/dep_node.rs

@@ -482,7 +482,7 @@ define_dep_nodes!( <'tcx>
     [] BorrowCheckKrate,
     [] BorrowCheck(DefId),
     [] MirBorrowCheck(DefId),
-    [] UnsafetyViolations(DefId),
+    [] UnsafetyCheckResult(DefId),
 
     [] Reachability,
     [] MirKeys,

src/librustc/ich/impls_mir.rs

@@ -34,6 +34,7 @@ impl_stable_hash_for!(struct mir::LocalDecl<'tcx> {
 impl_stable_hash_for!(struct mir::UpvarDecl { debug_name, by_ref });
 impl_stable_hash_for!(struct mir::BasicBlockData<'tcx> { statements, terminator, is_cleanup });
 impl_stable_hash_for!(struct mir::UnsafetyViolation { source_info, description, lint_node_id });
+impl_stable_hash_for!(struct mir::UnsafetyCheckResult { violations, unsafe_blocks });
 
 impl<'gcx> HashStable<StableHashingContext<'gcx>>
 for mir::Terminator<'gcx> {

src/librustc/mir/mod.rs

@@ -33,6 +33,7 @@ use std::cell::Ref;
 use std::fmt::{self, Debug, Formatter, Write};
 use std::{iter, u32};
 use std::ops::{Index, IndexMut};
+use std::rc::Rc;
 use std::vec::IntoIter;
 use syntax::ast::{self, Name};
 use syntax_pos::Span;
@@ -1683,6 +1684,15 @@ pub struct UnsafetyViolation {
     pub lint_node_id: Option<ast::NodeId>,
 }
 
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct UnsafetyCheckResult {
+    /// Violations that are propagated *upwards* from this function
+    pub violations: Rc<[UnsafetyViolation]>,
+    /// unsafe blocks in this function, along with whether they are used. This is
+    /// used for the "unused_unsafe" lint.
+    pub unsafe_blocks: Rc<[(ast::NodeId, bool)]>,
+}
+
 /// The layout of generator state
 #[derive(Clone, Debug, RustcEncodable, RustcDecodable)]
 pub struct GeneratorLayout<'tcx> {

src/librustc/ty/maps/mod.rs

@@ -171,9 +171,8 @@ define_maps! { <'tcx>
     /// expression defining the closure.
     [] fn closure_kind: ClosureKind(DefId) -> ty::ClosureKind,
 
-    /// Unsafety violations for this def ID.
-    [] fn unsafety_violations: UnsafetyViolations(DefId)
-        -> Rc<[mir::UnsafetyViolation]>,
+    /// The result of unsafety-checking this def-id.
+    [] fn unsafety_check_result: UnsafetyCheckResult(DefId) -> mir::UnsafetyCheckResult,
 
     /// The signature of functions and closures.
     [] fn fn_sig: FnSignature(DefId) -> ty::PolyFnSig<'tcx>,

src/librustc/ty/maps/plumbing.rs

@@ -720,7 +720,7 @@ pub fn force_from_dep_node<'a, 'gcx, 'lcx>(tcx: TyCtxt<'a, 'gcx, 'lcx>,
 
         DepKind::BorrowCheck => { force!(borrowck, def_id!()); }
         DepKind::MirBorrowCheck => { force!(mir_borrowck, def_id!()); }
-        DepKind::UnsafetyViolations => { force!(unsafety_violations, def_id!()); }
+        DepKind::UnsafetyCheckResult => { force!(unsafety_check_result, def_id!()); }
         DepKind::Reachability => { force!(reachable_set, LOCAL_CRATE); }
         DepKind::MirKeys => { force!(mir_keys, LOCAL_CRATE); }
         DepKind::CrateVariances => { force!(crate_variances, LOCAL_CRATE); }