we can get the Session from the TyCtxt

benches/helpers/miri_helper.rs

@@ -58,7 +58,7 @@ fn build_controller(
 
             let mut mir_map = MirMap { map: mir_map.map.clone() };
             run_mir_passes(tcx, &mut mir_map);
-            bencher.borrow_mut().iter(|| { eval_main(tcx, &mir_map, node_id, state.session); });
+            bencher.borrow_mut().iter(|| { eval_main(tcx, &mir_map, node_id); });
 
             state.session.abort_if_errors();
         });

src/bin/miri.rs

@@ -75,7 +75,7 @@ fn build_controller(
                 mir_map_copy.map.insert(def_id, mir_map.map.get(&def_id).unwrap().clone());
             }
             run_mir_passes(tcx, &mut mir_map_copy);
-            eval_main(tcx, &mir_map_copy, entry_def_id, memory_size, step_limit, stack_limit, state.session);
+            eval_main(tcx, &mir_map_copy, entry_def_id, memory_size, step_limit, stack_limit);
 
             state.session.abort_if_errors();
         });

src/interpreter/mod.rs

@@ -6,7 +6,6 @@
 use rustc::ty::layout::{self, Layout, Size};
 use rustc::ty::subst::{self, Subst, Substs};
 use rustc::ty::{self, Ty, TyCtxt, TypeFoldable};
-use rustc::session::Session;
 use rustc::util::nodemap::DefIdMap;
 use rustc_data_structures::indexed_vec::Idx;
 use std::cell::RefCell;
@@ -32,10 +31,6 @@ pub struct EvalContext<'a, 'tcx: 'a> {
     /// The results of the type checker, from rustc.
     tcx: TyCtxt<'a, 'tcx, 'tcx>,
 
-    /// The Session, from rustc.
-    /// Used to extract info from other crates
-    session: &'a Session,
-
     /// A mapping from NodeIds to Mir, from rustc. Only contains MIR for crate-local items.
     mir_map: &'a MirMap<'tcx>,
 
@@ -159,7 +154,7 @@ pub enum StackPopCleanup {
 }
 
 impl<'a, 'tcx> EvalContext<'a, 'tcx> {
-    pub fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>, mir_map: &'a MirMap<'tcx>, memory_size: usize, stack_limit: usize, session: &'a Session) -> Self {
+    pub fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>, mir_map: &'a MirMap<'tcx>, memory_size: usize, stack_limit: usize) -> Self {
         EvalContext {
             tcx: tcx,
             mir_map: mir_map,
@@ -168,7 +163,6 @@ pub fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>, mir_map: &'a MirMap<'tcx>, memory_size:
             statics: HashMap::new(),
             stack: Vec::new(),
             stack_limit: stack_limit,
-            session: session,
         }
     }
 
@@ -1197,10 +1191,9 @@ pub fn eval_main<'a, 'tcx: 'a>(
     memory_size: usize,
     step_limit: u64,
     stack_limit: usize,
-    session: &'a Session,
 ) {
     let mir = mir_map.map.get(&def_id).expect("no mir for main function");
-    let mut ecx = EvalContext::new(tcx, mir_map, memory_size, stack_limit, session);
+    let mut ecx = EvalContext::new(tcx, mir_map, memory_size, stack_limit);
     let substs = subst::Substs::empty(tcx);
     let return_ptr = ecx.alloc_ret_ptr(mir.return_ty, substs)
         .expect("should at least be able to allocate space for the main function's return value");

src/interpreter/step.rs

@@ -212,7 +212,7 @@ fn visit_lvalue(
                     bug!("static def id doesn't point to item");
                 }
             } else {
-                let def = self.ecx.session.cstore.describe_def(def_id).expect("static not found");
+                let def = self.ecx.tcx.sess.cstore.describe_def(def_id).expect("static not found");
                 if let hir::def::Def::Static(_, mutable) = def {
                     self.global_item(def_id, substs, span, !mutable);
                 } else {