diff --git a/src/librustc/middle/typeck/check/method.rs b/src/librustc/middle/typeck/check/method.rs
index 2892ad62b73..747c097f199 100644
--- a/src/librustc/middle/typeck/check/method.rs
+++ b/src/librustc/middle/typeck/check/method.rs
@@ -343,7 +343,7 @@ impl<'a> LookupContext<'a> {
         // If the method being called is associated with a trait, then
         // find all the impls of that trait.  Each of those are
         // candidates.
-        let trait_map: &mut resolve::TraitMap = &mut self.fcx.ccx.trait_map;
+        let trait_map: &resolve::TraitMap = &self.fcx.ccx.trait_map;
         let opt_applicable_traits = trait_map.find(&self.expr.id);
         for applicable_traits in opt_applicable_traits.iter() {
             for trait_did in applicable_traits.iter() {
diff --git a/src/librustc/middle/typeck/check/mod.rs b/src/librustc/middle/typeck/check/mod.rs
index 82f7ba2e88b..1b89cf67cab 100644
--- a/src/librustc/middle/typeck/check/mod.rs
+++ b/src/librustc/middle/typeck/check/mod.rs
@@ -251,7 +251,7 @@ pub struct FnCtxt {
 
     inh: @Inherited,
 
-    ccx: @mut CrateCtxt,
+    ccx: @CrateCtxt,
 }
 
 impl Inherited {
@@ -272,7 +272,7 @@ impl Inherited {
 }
 
 // Used by check_const and check_enum_variants
-pub fn blank_fn_ctxt(ccx: @mut CrateCtxt,
+pub fn blank_fn_ctxt(ccx: @CrateCtxt,
                      rty: ty::t,
                      region_bnd: ast::NodeId)
                      -> @FnCtxt {
@@ -302,7 +302,7 @@ impl ExprTyProvider for FnCtxt {
     }
 }
 
-struct CheckItemTypesVisitor { ccx: @mut CrateCtxt }
+struct CheckItemTypesVisitor { ccx: @CrateCtxt }
 
 impl Visitor<()> for CheckItemTypesVisitor {
     fn visit_item(&mut self, i:@ast::item, _:()) {
@@ -311,12 +311,12 @@ impl Visitor<()> for CheckItemTypesVisitor {
     }
 }
 
-pub fn check_item_types(ccx: @mut CrateCtxt, crate: &ast::Crate) {
+pub fn check_item_types(ccx: @CrateCtxt, crate: &ast::Crate) {
     let mut visit = CheckItemTypesVisitor { ccx: ccx };
     visit::walk_crate(&mut visit, crate, ());
 }
 
-pub fn check_bare_fn(ccx: @mut CrateCtxt,
+pub fn check_bare_fn(ccx: @CrateCtxt,
                      decl: &ast::fn_decl,
                      body: ast::P<ast::Block>,
                      id: ast::NodeId,
@@ -407,7 +407,7 @@ impl Visitor<()> for GatherLocalsVisitor {
 
 }
 
-pub fn check_fn(ccx: @mut CrateCtxt,
+pub fn check_fn(ccx: @CrateCtxt,
                 opt_self_info: Option<SelfInfo>,
                 purity: ast::purity,
                 fn_sig: &ty::FnSig,
@@ -556,7 +556,7 @@ pub fn check_no_duplicate_fields(tcx: ty::ctxt,
     }
 }
 
-pub fn check_struct(ccx: @mut CrateCtxt, id: ast::NodeId, span: Span) {
+pub fn check_struct(ccx: @CrateCtxt, id: ast::NodeId, span: Span) {
     let tcx = ccx.tcx;
 
     // Check that the class is instantiable
@@ -567,7 +567,7 @@ pub fn check_struct(ccx: @mut CrateCtxt, id: ast::NodeId, span: Span) {
     }
 }
 
-pub fn check_item(ccx: @mut CrateCtxt, it: @ast::item) {
+pub fn check_item(ccx: @CrateCtxt, it: @ast::item) {
     debug!("check_item(it.id={}, it.ident={})",
            it.id,
            ty::item_path_str(ccx.tcx, local_def(it.id)));
@@ -670,7 +670,7 @@ pub fn check_item(ccx: @mut CrateCtxt, it: @ast::item) {
     }
 }
 
-fn check_method_body(ccx: @mut CrateCtxt,
+fn check_method_body(ccx: @CrateCtxt,
                      item_generics: &ty::Generics,
                      self_bound: Option<@ty::TraitRef>,
                      method: @ast::method) {
@@ -722,7 +722,7 @@ fn check_method_body(ccx: @mut CrateCtxt,
         param_env);
 }
 
-fn check_impl_methods_against_trait(ccx: @mut CrateCtxt,
+fn check_impl_methods_against_trait(ccx: @CrateCtxt,
                                     impl_span: Span,
                                     impl_generics: &ty::Generics,
                                     ast_trait_ref: &ast::trait_ref,
@@ -1388,7 +1388,7 @@ pub fn check_lit(fcx: @FnCtxt, lit: @ast::lit) -> ty::t {
     }
 }
 
-pub fn valid_range_bounds(ccx: @mut CrateCtxt,
+pub fn valid_range_bounds(ccx: @CrateCtxt,
                           from: @ast::Expr,
                           to: @ast::Expr)
                        -> Option<bool> {
@@ -3443,7 +3443,7 @@ pub fn check_block_with_expected(fcx: @FnCtxt,
     fcx.ps.set(prev);
 }
 
-pub fn check_const(ccx: @mut CrateCtxt,
+pub fn check_const(ccx: @CrateCtxt,
                    sp: Span,
                    e: @ast::Expr,
                    id: ast::NodeId) {
@@ -3519,15 +3519,15 @@ pub fn check_simd(tcx: ty::ctxt, sp: Span, id: ast::NodeId) {
     }
 }
 
-pub fn check_enum_variants(ccx: @mut CrateCtxt,
+pub fn check_enum_variants(ccx: @CrateCtxt,
                            sp: Span,
                            vs: &[ast::P<ast::variant>],
                            id: ast::NodeId) {
 
-    fn disr_in_range(ccx: @mut CrateCtxt,
+    fn disr_in_range(ccx: @CrateCtxt,
                      ty: attr::IntType,
                      disr: ty::Disr) -> bool {
-        fn uint_in_range(ccx: @mut CrateCtxt, ty: ast::uint_ty, disr: ty::Disr) -> bool {
+        fn uint_in_range(ccx: @CrateCtxt, ty: ast::uint_ty, disr: ty::Disr) -> bool {
             match ty {
                 ast::ty_u8 => disr as u8 as Disr == disr,
                 ast::ty_u16 => disr as u16 as Disr == disr,
@@ -3536,7 +3536,7 @@ pub fn check_enum_variants(ccx: @mut CrateCtxt,
                 ast::ty_u => uint_in_range(ccx, ccx.tcx.sess.targ_cfg.uint_type, disr)
             }
         }
-        fn int_in_range(ccx: @mut CrateCtxt, ty: ast::int_ty, disr: ty::Disr) -> bool {
+        fn int_in_range(ccx: @CrateCtxt, ty: ast::int_ty, disr: ty::Disr) -> bool {
             match ty {
                 ast::ty_i8 => disr as i8 as Disr == disr,
                 ast::ty_i16 => disr as i16 as Disr == disr,
@@ -3551,7 +3551,7 @@ pub fn check_enum_variants(ccx: @mut CrateCtxt,
         }
     }
 
-    fn do_check(ccx: @mut CrateCtxt,
+    fn do_check(ccx: @CrateCtxt,
                 vs: &[ast::P<ast::variant>],
                 id: ast::NodeId,
                 hint: attr::ReprAttr)
@@ -3923,7 +3923,7 @@ pub fn may_break(cx: ty::ctxt, id: ast::NodeId, b: ast::P<ast::Block>) -> bool {
         }}))
 }
 
-pub fn check_bounds_are_used(ccx: @mut CrateCtxt,
+pub fn check_bounds_are_used(ccx: @CrateCtxt,
                              span: Span,
                              tps: &OptVec<ast::TyParam>,
                              ty: ty::t) {
@@ -3953,8 +3953,8 @@ pub fn check_bounds_are_used(ccx: @mut CrateCtxt,
     }
 }
 
-pub fn check_intrinsic_type(ccx: @mut CrateCtxt, it: @ast::foreign_item) {
-    fn param(ccx: @mut CrateCtxt, n: uint) -> ty::t {
+pub fn check_intrinsic_type(ccx: @CrateCtxt, it: @ast::foreign_item) {
+    fn param(ccx: @CrateCtxt, n: uint) -> ty::t {
         ty::mk_param(ccx.tcx, n, local_def(0))
     }
 
diff --git a/src/librustc/middle/typeck/check/vtable.rs b/src/librustc/middle/typeck/check/vtable.rs
index c6636db8393..dc17a082201 100644
--- a/src/librustc/middle/typeck/check/vtable.rs
+++ b/src/librustc/middle/typeck/check/vtable.rs
@@ -728,7 +728,7 @@ fn resolve_expr(fcx: @FnCtxt,
     visit::walk_expr(&mut fcx, ex, ());
 }
 
-pub fn resolve_impl(ccx: @mut CrateCtxt,
+pub fn resolve_impl(ccx: @CrateCtxt,
                     impl_item: @ast::item,
                     impl_generics: &ty::Generics,
                     impl_trait_ref: &ty::TraitRef) {
diff --git a/src/librustc/middle/typeck/coherence.rs b/src/librustc/middle/typeck/coherence.rs
index 6244c116bae..5bca8b4432c 100644
--- a/src/librustc/middle/typeck/coherence.rs
+++ b/src/librustc/middle/typeck/coherence.rs
@@ -142,7 +142,7 @@ pub fn get_base_type_def_id(inference_context: @mut InferCtxt,
     }
 }
 
-pub fn CoherenceChecker(crate_context: @mut CrateCtxt) -> CoherenceChecker {
+pub fn CoherenceChecker(crate_context: @CrateCtxt) -> CoherenceChecker {
     CoherenceChecker {
         crate_context: crate_context,
         inference_context: new_infer_ctxt(crate_context.tcx),
@@ -150,7 +150,7 @@ pub fn CoherenceChecker(crate_context: @mut CrateCtxt) -> CoherenceChecker {
 }
 
 pub struct CoherenceChecker {
-    crate_context: @mut CrateCtxt,
+    crate_context: @CrateCtxt,
     inference_context: @mut InferCtxt,
 }
 
@@ -825,7 +825,7 @@ fn subst_receiver_types_in_method_ty(tcx: ty::ctxt,
     )
 }
 
-pub fn check_coherence(crate_context: @mut CrateCtxt, crate: &Crate) {
+pub fn check_coherence(crate_context: @CrateCtxt, crate: &Crate) {
     let coherence_checker = CoherenceChecker(crate_context);
     coherence_checker.check_coherence(crate);
 }
diff --git a/src/librustc/middle/typeck/collect.rs b/src/librustc/middle/typeck/collect.rs
index c860310ade4..3dfcf15e024 100644
--- a/src/librustc/middle/typeck/collect.rs
+++ b/src/librustc/middle/typeck/collect.rs
@@ -57,7 +57,7 @@ use syntax::opt_vec::OptVec;
 use syntax::parse::token::special_idents;
 
 struct CollectItemTypesVisitor {
-    ccx: @mut CrateCtxt
+    ccx: @CrateCtxt
 }
 
 impl visit::Visitor<()> for CollectItemTypesVisitor {
@@ -71,7 +71,7 @@ impl visit::Visitor<()> for CollectItemTypesVisitor {
     }
 }
 
-pub fn collect_item_types(ccx: @mut CrateCtxt, crate: &ast::Crate) {
+pub fn collect_item_types(ccx: @CrateCtxt, crate: &ast::Crate) {
     fn collect_intrinsic_type(ccx: &CrateCtxt,
                               lang_item: ast::DefId) {
         let ty::ty_param_bounds_and_ty { ty: ty, .. } =
diff --git a/src/librustc/middle/typeck/mod.rs b/src/librustc/middle/typeck/mod.rs
index 2da5c09e002..62fb7390fa4 100644
--- a/src/librustc/middle/typeck/mod.rs
+++ b/src/librustc/middle/typeck/mod.rs
@@ -456,7 +456,7 @@ pub fn check_crate(tcx: ty::ctxt,
                    crate: &ast::Crate)
                 -> (method_map, vtable_map) {
     let time_passes = tcx.sess.time_passes();
-    let ccx = @mut CrateCtxt {
+    let ccx = @CrateCtxt {
         trait_map: trait_map,
         method_map: @mut HashMap::new(),
         vtable_map: @RefCell::new(HashMap::new()),