diff --git a/src/librustc/middle/ty/relate.rs b/src/librustc/middle/ty/relate.rs
index 46bc13bd598..974b5c4bc6c 100644
--- a/src/librustc/middle/ty/relate.rs
+++ b/src/librustc/middle/ty/relate.rs
@@ -105,8 +105,8 @@ impl<'a,'tcx:'a> Relate<'a,'tcx> for ty::TypeAndMut<'tcx> {
         } else {
             let mutbl = a.mutbl;
             let variance = match mutbl {
-                ast::MutImmutable => ty::Covariant,
-                ast::MutMutable => ty::Invariant,
+                ast::Mutability::MutImmutable => ty::Covariant,
+                ast::Mutability::MutMutable => ty::Invariant,
             };
             let ty = try!(relation.relate_with_variance(variance, &a.ty, &b.ty));
             Ok(ty::TypeAndMut {ty: ty, mutbl: mutbl})
diff --git a/src/librustc_front/lowering.rs b/src/librustc_front/lowering.rs
index d04f4c96504..e9dfa1bd164 100644
--- a/src/librustc_front/lowering.rs
+++ b/src/librustc_front/lowering.rs
@@ -427,8 +427,8 @@ pub fn lower_explicit_self_underscore(lctx: &LoweringContext,
 
 pub fn lower_mutability(_lctx: &LoweringContext, m: Mutability) -> hir::Mutability {
     match m {
-        MutMutable => hir::MutMutable,
-        MutImmutable => hir::MutImmutable,
+        Mutability::Mutable => hir::MutMutable,
+        Mutability::Immutable => hir::MutImmutable,
     }
 }
 
diff --git a/src/librustc_passes/const_fn.rs b/src/librustc_passes/const_fn.rs
index 98346f538b0..edbc6424ccd 100644
--- a/src/librustc_passes/const_fn.rs
+++ b/src/librustc_passes/const_fn.rs
@@ -105,7 +105,7 @@ impl<'a, 'v> Visitor<'v> for CheckConstFn<'a> {
         for arg in &fd.inputs {
             match arg.pat.node {
                 ast::PatWild => {}
-                ast::PatIdent(ast::BindingMode::ByValue(ast::MutImmutable), _, None) => {}
+                ast::PatIdent(ast::BindingMode::ByValue(ast::Mutability::Immutable), _, None) => {}
                 _ => {
                     span_err!(self.sess, arg.pat.span, E0022,
                               "arguments of constant functions can only \
diff --git a/src/librustc_trans/save/dump_csv.rs b/src/librustc_trans/save/dump_csv.rs
index d8f21fd4dd6..68c04427c65 100644
--- a/src/librustc_trans/save/dump_csv.rs
+++ b/src/librustc_trans/save/dump_csv.rs
@@ -807,7 +807,7 @@ impl <'l, 'tcx> DumpCsvVisitor<'l, 'tcx> {
         self.visit_pat(&p);
 
         for &(id, ref p, immut, _) in &collector.collected_paths {
-            let value = if immut == ast::MutImmutable {
+            let value = if immut == ast::Mutability::Immutable {
                 value.to_string()
             } else {
                 "<mutable>".to_string()
@@ -1200,7 +1200,7 @@ impl<'l, 'tcx, 'v> Visitor<'v> for DumpCsvVisitor<'l, 'tcx> {
             let def = def_map.get(&id).unwrap().full_def();
             match def {
                 Def::Local(_, id) => {
-                    let value = if immut == ast::MutImmutable {
+                    let value = if immut == ast::Mutability::Immutable {
                         self.span.snippet(p.span).to_string()
                     } else {
                         "<mutable>".to_string()
diff --git a/src/librustc_trans/save/mod.rs b/src/librustc_trans/save/mod.rs
index 1790da39ad0..ff19640d645 100644
--- a/src/librustc_trans/save/mod.rs
+++ b/src/librustc_trans/save/mod.rs
@@ -248,8 +248,10 @@ impl<'l, 'tcx: 'l> SaveContext<'l, 'tcx> {
 
                 // If the variable is immutable, save the initialising expression.
                 let (value, keyword) = match mt {
-                    ast::MutMutable => (String::from("<mutable>"), keywords::Mut),
-                    ast::MutImmutable => (self.span_utils.snippet(expr.span), keywords::Static),
+                    ast::Mutability::Mutable => (String::from("<mutable>"), keywords::Mut),
+                    ast::Mutability::Immutable => {
+                        (self.span_utils.snippet(expr.span), keywords::Static)
+                    },
                 };
 
                 let sub_span = self.span_utils.sub_span_after_keyword(item.span, keyword);
@@ -758,12 +760,12 @@ impl<'v> Visitor<'v> for PathCollector {
         match p.node {
             ast::PatStruct(ref path, _, _) => {
                 self.collected_paths.push((p.id, path.clone(),
-                                           ast::MutMutable, recorder::TypeRef));
+                                           ast::Mutability::Mutable, recorder::TypeRef));
             }
             ast::PatEnum(ref path, _) |
             ast::PatQPath(_, ref path) => {
                 self.collected_paths.push((p.id, path.clone(),
-                                           ast::MutMutable, recorder::VarRef));
+                                           ast::Mutability::Mutable, recorder::VarRef));
             }
             ast::PatIdent(bm, ref path1, _) => {
                 debug!("PathCollector, visit ident in pat {}: {:?} {:?}",
@@ -774,7 +776,7 @@ impl<'v> Visitor<'v> for PathCollector {
                     // Even if the ref is mut, you can't change the ref, only
                     // the data pointed at, so showing the initialising expression
                     // is still worthwhile.
-                    ast::BindingMode::ByRef(_) => ast::MutImmutable,
+                    ast::BindingMode::ByRef(_) => ast::Mutability::Immutable,
                     ast::BindingMode::ByValue(mt) => mt,
                 };
                 // collect path for either visit_local or visit_arm
diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index a3a59b7898b..cfaa5fc4a96 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -10,7 +10,6 @@
 
 // The Rust abstract syntax tree.
 
-pub use self::Mutability::*;
 pub use self::Pat_::*;
 pub use self::PathListItem_::*;
 pub use self::StrStyle::*;
@@ -602,8 +601,8 @@ pub enum Pat_ {
 
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
 pub enum Mutability {
-    MutMutable,
-    MutImmutable,
+    Mutable,
+    Immutable,
 }
 
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
diff --git a/src/libsyntax/ast_util.rs b/src/libsyntax/ast_util.rs
index 270133ad599..e22cdab97e8 100644
--- a/src/libsyntax/ast_util.rs
+++ b/src/libsyntax/ast_util.rs
@@ -66,9 +66,10 @@ pub fn path_to_ident(path: &Path) -> Option<Ident> {
 }
 
 pub fn ident_to_pat(id: NodeId, s: Span, i: Ident) -> P<Pat> {
+    let spanned = codemap::Spanned{ span: s, node: i };
     P(Pat {
         id: id,
-        node: PatIdent(BindingMode::ByValue(MutImmutable), codemap::Spanned{span:s, node:i}, None),
+        node: PatIdent(BindingMode::ByValue(Mutability::Immutable), spanned, None),
         span: s
     })
 }
diff --git a/src/libsyntax/diagnostics/plugin.rs b/src/libsyntax/diagnostics/plugin.rs
index e8a4bb59bdc..2e343948c42 100644
--- a/src/libsyntax/diagnostics/plugin.rs
+++ b/src/libsyntax/diagnostics/plugin.rs
@@ -207,7 +207,7 @@ pub fn expand_build_diagnostic_array<'cx>(ecx: &'cx mut ExtCtxt,
         span,
         ecx.ty_ident(span, ecx.ident_of("str")),
         Some(static_),
-        ast::MutImmutable,
+        ast::Mutability::Immutable,
     );
 
     let ty = ecx.ty(
diff --git a/src/libsyntax/ext/build.rs b/src/libsyntax/ext/build.rs
index a807fbb93fb..e32dcc99a0e 100644
--- a/src/libsyntax/ext/build.rs
+++ b/src/libsyntax/ext/build.rs
@@ -512,7 +512,8 @@ impl<'a> AstBuilder for ExtCtxt<'a> {
     fn stmt_let(&self, sp: Span, mutbl: bool, ident: ast::Ident,
                 ex: P<ast::Expr>) -> P<ast::Stmt> {
         let pat = if mutbl {
-            self.pat_ident_binding_mode(sp, ident, ast::BindingMode::ByValue(ast::MutMutable))
+            let binding_mode = ast::BindingMode::ByValue(ast::Mutability::Mutable);
+            self.pat_ident_binding_mode(sp, ident, binding_mode)
         } else {
             self.pat_ident(sp, ident)
         };
@@ -536,7 +537,8 @@ impl<'a> AstBuilder for ExtCtxt<'a> {
                       ex: P<ast::Expr>)
                       -> P<ast::Stmt> {
         let pat = if mutbl {
-            self.pat_ident_binding_mode(sp, ident, ast::BindingMode::ByValue(ast::MutMutable))
+            let binding_mode = ast::BindingMode::ByValue(ast::Mutability::Mutable);
+            self.pat_ident_binding_mode(sp, ident, binding_mode)
         } else {
             self.pat_ident(sp, ident)
         };
@@ -636,10 +638,10 @@ impl<'a> AstBuilder for ExtCtxt<'a> {
         self.expr(sp, ast::ExprKind::TupField(expr, id))
     }
     fn expr_addr_of(&self, sp: Span, e: P<ast::Expr>) -> P<ast::Expr> {
-        self.expr(sp, ast::ExprKind::AddrOf(ast::MutImmutable, e))
+        self.expr(sp, ast::ExprKind::AddrOf(ast::Mutability::Immutable, e))
     }
     fn expr_mut_addr_of(&self, sp: Span, e: P<ast::Expr>) -> P<ast::Expr> {
-        self.expr(sp, ast::ExprKind::AddrOf(ast::MutMutable, e))
+        self.expr(sp, ast::ExprKind::AddrOf(ast::Mutability::Mutable, e))
     }
 
     fn expr_call(&self, span: Span, expr: P<ast::Expr>, args: Vec<P<ast::Expr>>) -> P<ast::Expr> {
@@ -813,7 +815,8 @@ impl<'a> AstBuilder for ExtCtxt<'a> {
         self.pat(span, ast::PatLit(expr))
     }
     fn pat_ident(&self, span: Span, ident: ast::Ident) -> P<ast::Pat> {
-        self.pat_ident_binding_mode(span, ident, ast::BindingMode::ByValue(ast::MutImmutable))
+        let binding_mode = ast::BindingMode::ByValue(ast::Mutability::Immutable);
+        self.pat_ident_binding_mode(span, ident, binding_mode)
     }
 
     fn pat_ident_binding_mode(&self,
diff --git a/src/libsyntax/parse/mod.rs b/src/libsyntax/parse/mod.rs
index a505b27e9db..850b4365256 100644
--- a/src/libsyntax/parse/mod.rs
+++ b/src/libsyntax/parse/mod.rs
@@ -896,7 +896,7 @@ mod tests {
         assert!(panictry!(parser.parse_pat())
                 == P(ast::Pat{
                 id: ast::DUMMY_NODE_ID,
-                node: ast::PatIdent(ast::BindingMode::ByValue(ast::MutImmutable),
+                node: ast::PatIdent(ast::BindingMode::ByValue(ast::Mutability::Immutable),
                                     Spanned{ span:sp(0, 1),
                                              node: str_to_ident("b")
                     },
@@ -932,7 +932,7 @@ mod tests {
                                     pat: P(ast::Pat {
                                         id: ast::DUMMY_NODE_ID,
                                         node: ast::PatIdent(
-                                            ast::BindingMode::ByValue(ast::MutImmutable),
+                                            ast::BindingMode::ByValue(ast::Mutability::Immutable),
                                                 Spanned{
                                                     span: sp(6,7),
                                                     node: str_to_ident("b")},
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 0875d054564..11638a3d424 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -27,7 +27,7 @@ use ast::{Ident, Inherited, ImplItem, Item, ItemKind};
 use ast::{Lit, LitKind, UintTy};
 use ast::Local;
 use ast::MacStmtStyle;
-use ast::{MutImmutable, MutMutable, Mac_};
+use ast::Mac_;
 use ast::{MutTy, Mutability};
 use ast::NamedField;
 use ast::{Pat, PatBox, PatEnum, PatIdent, PatLit, PatQPath, PatMac, PatRange};
@@ -1417,16 +1417,16 @@ impl<'a> Parser<'a> {
 
     pub fn parse_ptr(&mut self) -> PResult<'a, MutTy> {
         let mutbl = if self.eat_keyword(keywords::Mut) {
-            MutMutable
+            Mutability::Mutable
         } else if self.eat_keyword(keywords::Const) {
-            MutImmutable
+            Mutability::Immutable
         } else {
             let span = self.last_span;
             self.span_err(span,
                           "bare raw pointers are no longer allowed, you should \
                            likely use `*mut T`, but otherwise `*T` is now \
                            known as `*const T`");
-            MutImmutable
+            Mutability::Immutable
         };
         let t = try!(self.parse_ty());
         Ok(MutTy { ty: t, mutbl: mutbl })
@@ -1924,9 +1924,9 @@ impl<'a> Parser<'a> {
     /// Parse mutability declaration (mut/const/imm)
     pub fn parse_mutability(&mut self) -> PResult<'a, Mutability> {
         if self.eat_keyword(keywords::Mut) {
-            Ok(MutMutable)
+            Ok(Mutability::Mutable)
         } else {
-            Ok(MutImmutable)
+            Ok(Mutability::Immutable)
         }
     }
 
@@ -3350,10 +3350,10 @@ impl<'a> Parser<'a> {
                 hi = self.last_span.hi;
 
                 let bind_type = match (is_ref, is_mut) {
-                    (true, true) => BindingMode::ByRef(MutMutable),
-                    (true, false) => BindingMode::ByRef(MutImmutable),
-                    (false, true) => BindingMode::ByValue(MutMutable),
-                    (false, false) => BindingMode::ByValue(MutImmutable),
+                    (true, true) => BindingMode::ByRef(Mutability::Mutable),
+                    (true, false) => BindingMode::ByRef(Mutability::Immutable),
+                    (false, true) => BindingMode::ByValue(Mutability::Mutable),
+                    (false, false) => BindingMode::ByValue(Mutability::Immutable),
                 };
                 let fieldpath = codemap::Spanned{span:self.last_span, node:fieldname};
                 let fieldpat = P(ast::Pat{
@@ -3448,7 +3448,7 @@ impl<'a> Parser<'a> {
             // At this point, token != _, &, &&, (, [
             if self.eat_keyword(keywords::Mut) {
                 // Parse mut ident @ pat
-                pat = try!(self.parse_pat_ident(BindingMode::ByValue(MutMutable)));
+                pat = try!(self.parse_pat_ident(BindingMode::ByValue(Mutability::Mutable)));
             } else if self.eat_keyword(keywords::Ref) {
                 // Parse ref ident @ pat / ref mut ident @ pat
                 let mutbl = try!(self.parse_mutability());
@@ -3481,7 +3481,8 @@ impl<'a> Parser<'a> {
                         // Parse ident @ pat
                         // This can give false positives and parse nullary enums,
                         // they are dealt with later in resolve
-                        pat = try!(self.parse_pat_ident(BindingMode::ByValue(MutImmutable)));
+                        let binding_mode = BindingMode::ByValue(Mutability::Immutable);
+                        pat = try!(self.parse_pat_ident(binding_mode));
                     }
                 } else {
                     let (qself, path) = if self.eat_lt() {
@@ -4408,7 +4409,7 @@ impl<'a> Parser<'a> {
 
             if this.look_ahead(1, |t| t.is_keyword(keywords::SelfValue)) {
                 this.bump();
-                Ok(SelfKind::Region(None, MutImmutable, try!(this.expect_self_ident())))
+                Ok(SelfKind::Region(None, Mutability::Immutable, try!(this.expect_self_ident())))
             } else if this.look_ahead(1, |t| t.is_mutability()) &&
                       this.look_ahead(2, |t| t.is_keyword(keywords::SelfValue)) {
                 this.bump();
@@ -4418,7 +4419,8 @@ impl<'a> Parser<'a> {
                       this.look_ahead(2, |t| t.is_keyword(keywords::SelfValue)) {
                 this.bump();
                 let lifetime = try!(this.parse_lifetime());
-                Ok(SelfKind::Region(Some(lifetime), MutImmutable, try!(this.expect_self_ident())))
+                let ident = try!(this.expect_self_ident());
+                Ok(SelfKind::Region(Some(lifetime), Mutability::Immutable, ident))
             } else if this.look_ahead(1, |t| t.is_lifetime()) &&
                       this.look_ahead(2, |t| t.is_mutability()) &&
                       this.look_ahead(3, |t| t.is_keyword(keywords::SelfValue)) {
@@ -4439,7 +4441,7 @@ impl<'a> Parser<'a> {
         let mut self_ident_lo = self.span.lo;
         let mut self_ident_hi = self.span.hi;
 
-        let mut mutbl_self = MutImmutable;
+        let mut mutbl_self = Mutability::Immutable;
         let explicit_self = match self.token {
             token::BinOp(token::And) => {
                 let eself = try!(maybe_parse_borrowed_explicit_self(self));
@@ -4454,7 +4456,7 @@ impl<'a> Parser<'a> {
                 let _mutability = if self.token.is_mutability() {
                     try!(self.parse_mutability())
                 } else {
-                    MutImmutable
+                    Mutability::Immutable
                 };
                 if self.is_self_ident() {
                     let span = self.span;
@@ -5527,7 +5529,11 @@ impl<'a> Parser<'a> {
 
         if self.eat_keyword(keywords::Static) {
             // STATIC ITEM
-            let m = if self.eat_keyword(keywords::Mut) {MutMutable} else {MutImmutable};
+            let m = if self.eat_keyword(keywords::Mut) {
+                Mutability::Mutable
+            } else {
+                Mutability::Immutable
+            };
             let (ident, item_, extra_attrs) = try!(self.parse_item_const(Some(m)));
             let last_span = self.last_span;
             let item = self.mk_item(lo,
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index 8495853c2c9..b14117c9704 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -417,7 +417,7 @@ pub fn lit_to_string(l: &ast::Lit) -> String {
 }
 
 pub fn explicit_self_to_string(explicit_self: &ast::SelfKind) -> String {
-    to_string(|s| s.print_explicit_self(explicit_self, ast::MutImmutable).map(|_| {}))
+    to_string(|s| s.print_explicit_self(explicit_self, ast::Mutability::Immutable).map(|_| {}))
 }
 
 pub fn variant_to_string(var: &ast::Variant) -> String {
@@ -965,8 +965,8 @@ impl<'a> State<'a> {
             ast::TyKind::Ptr(ref mt) => {
                 try!(word(&mut self.s, "*"));
                 match mt.mutbl {
-                    ast::MutMutable => try!(self.word_nbsp("mut")),
-                    ast::MutImmutable => try!(self.word_nbsp("const")),
+                    ast::Mutability::Mutable => try!(self.word_nbsp("mut")),
+                    ast::Mutability::Immutable => try!(self.word_nbsp("const")),
                 }
                 try!(self.print_type(&*mt.ty));
             }
@@ -1147,7 +1147,7 @@ impl<'a> State<'a> {
             ast::ItemKind::Static(ref ty, m, ref expr) => {
                 try!(self.head(&visibility_qualified(item.vis,
                                                     "static")));
-                if m == ast::MutMutable {
+                if m == ast::Mutability::Mutable {
                     try!(self.word_space("mut"));
                 }
                 try!(self.print_ident(item.ident));
@@ -2464,8 +2464,8 @@ impl<'a> State<'a> {
                         try!(self.word_nbsp("ref"));
                         try!(self.print_mutability(mutbl));
                     }
-                    ast::BindingMode::ByValue(ast::MutImmutable) => {}
-                    ast::BindingMode::ByValue(ast::MutMutable) => {
+                    ast::BindingMode::ByValue(ast::Mutability::Immutable) => {}
+                    ast::BindingMode::ByValue(ast::Mutability::Mutable) => {
                         try!(self.word_nbsp("mut"));
                     }
                 }
@@ -2534,7 +2534,7 @@ impl<'a> State<'a> {
             }
             ast::PatRegion(ref inner, mutbl) => {
                 try!(word(&mut self.s, "&"));
-                if mutbl == ast::MutMutable {
+                if mutbl == ast::Mutability::Mutable {
                     try!(word(&mut self.s, "mut "));
                 }
                 try!(self.print_pat(&**inner));
@@ -2669,10 +2669,10 @@ impl<'a> State<'a> {
         let mut first = true;
         if let Some(explicit_self) = opt_explicit_self {
             let m = match *explicit_self {
-                ast::SelfKind::Static => ast::MutImmutable,
+                ast::SelfKind::Static => ast::Mutability::Immutable,
                 _ => match decl.inputs[0].pat.node {
                     ast::PatIdent(ast::BindingMode::ByValue(m), _, _) => m,
-                    _ => ast::MutImmutable
+                    _ => ast::Mutability::Immutable
                 }
             };
             first = !try!(self.print_explicit_self(explicit_self, m));
@@ -2946,8 +2946,8 @@ impl<'a> State<'a> {
     pub fn print_mutability(&mut self,
                             mutbl: ast::Mutability) -> io::Result<()> {
         match mutbl {
-            ast::MutMutable => self.word_nbsp("mut"),
-            ast::MutImmutable => Ok(()),
+            ast::Mutability::Mutable => self.word_nbsp("mut"),
+            ast::Mutability::Immutable => Ok(()),
         }
     }
 
diff --git a/src/libsyntax/test.rs b/src/libsyntax/test.rs
index a817eb62af8..92ecadd7ae8 100644
--- a/src/libsyntax/test.rs
+++ b/src/libsyntax/test.rs
@@ -593,7 +593,7 @@ fn mk_tests(cx: &TestCtxt) -> P<ast::Item> {
     let static_type = ecx.ty_rptr(sp,
                                   ecx.ty(sp, ast::TyKind::Vec(struct_type)),
                                   Some(static_lt),
-                                  ast::MutImmutable);
+                                  ast::Mutability::Immutable);
     // static TESTS: $static_type = &[...];
     ecx.item_const(sp,
                    ecx.ident_of("TESTS"),
@@ -613,7 +613,7 @@ fn mk_test_descs(cx: &TestCtxt) -> P<ast::Expr> {
 
     P(ast::Expr {
         id: ast::DUMMY_NODE_ID,
-        node: ast::ExprKind::AddrOf(ast::MutImmutable,
+        node: ast::ExprKind::AddrOf(ast::Mutability::Immutable,
             P(ast::Expr {
                 id: ast::DUMMY_NODE_ID,
                 node: ast::ExprKind::Vec(cx.testfns.iter().map(|test| {
diff --git a/src/libsyntax_ext/deriving/debug.rs b/src/libsyntax_ext/deriving/debug.rs
index 917c6b1ab89..6e769cd3810 100644
--- a/src/libsyntax_ext/deriving/debug.rs
+++ b/src/libsyntax_ext/deriving/debug.rs
@@ -27,7 +27,7 @@ pub fn expand_deriving_debug(cx: &mut ExtCtxt,
 {
     // &mut ::std::fmt::Formatter
     let fmtr = Ptr(Box::new(Literal(path_std!(cx, core::fmt::Formatter))),
-                   Borrowed(None, ast::MutMutable));
+                   Borrowed(None, ast::Mutability::Mutable));
 
     let trait_def = TraitDef {
         span: span,
diff --git a/src/libsyntax_ext/deriving/decodable.rs b/src/libsyntax_ext/deriving/decodable.rs
index 4ea4f04623a..092f8548966 100644
--- a/src/libsyntax_ext/deriving/decodable.rs
+++ b/src/libsyntax_ext/deriving/decodable.rs
@@ -14,7 +14,7 @@ use deriving::generic::*;
 use deriving::generic::ty::*;
 
 use syntax::ast;
-use syntax::ast::{MetaItem, Expr, MutMutable};
+use syntax::ast::{MetaItem, Expr, Mutability};
 use syntax::codemap::Span;
 use syntax::ext::base::{ExtCtxt, Annotatable};
 use syntax::ext::build::AstBuilder;
@@ -72,7 +72,7 @@ fn expand_deriving_decodable_imp(cx: &mut ExtCtxt,
                 },
                 explicit_self: None,
                 args: vec!(Ptr(Box::new(Literal(Path::new_local("__D"))),
-                            Borrowed(None, MutMutable))),
+                            Borrowed(None, Mutability::Mutable))),
                 ret_ty: Literal(Path::new_(
                     pathvec_std!(cx, core::result::Result),
                     None,
diff --git a/src/libsyntax_ext/deriving/encodable.rs b/src/libsyntax_ext/deriving/encodable.rs
index 14631659b0b..614a6381962 100644
--- a/src/libsyntax_ext/deriving/encodable.rs
+++ b/src/libsyntax_ext/deriving/encodable.rs
@@ -91,7 +91,7 @@
 use deriving::generic::*;
 use deriving::generic::ty::*;
 
-use syntax::ast::{MetaItem, Expr, ExprKind, MutMutable};
+use syntax::ast::{MetaItem, Expr, ExprKind, Mutability};
 use syntax::codemap::Span;
 use syntax::ext::base::{ExtCtxt,Annotatable};
 use syntax::ext::build::AstBuilder;
@@ -148,7 +148,7 @@ fn expand_deriving_encodable_imp(cx: &mut ExtCtxt,
                 },
                 explicit_self: borrowed_explicit_self(),
                 args: vec!(Ptr(Box::new(Literal(Path::new_local("__S"))),
-                            Borrowed(None, MutMutable))),
+                            Borrowed(None, Mutability::Mutable))),
                 ret_ty: Literal(Path::new_(
                     pathvec_std!(cx, core::result::Result),
                     None,
diff --git a/src/libsyntax_ext/deriving/generic/mod.rs b/src/libsyntax_ext/deriving/generic/mod.rs
index 51091b84672..b316b1e7d86 100644
--- a/src/libsyntax_ext/deriving/generic/mod.rs
+++ b/src/libsyntax_ext/deriving/generic/mod.rs
@@ -864,7 +864,9 @@ impl<'a> MethodDef<'a> {
         let self_arg = match explicit_self.node {
             ast::SelfKind::Static => None,
             // creating fresh self id
-            _ => Some(ast::Arg::new_self(trait_.span, ast::MutImmutable, special_idents::self_))
+            _ => Some(ast::Arg::new_self(trait_.span,
+                                         ast::Mutability::Immutable,
+                                         special_idents::self_))
         };
         let args = {
             let args = arg_types.into_iter().map(|(name, ty)| {
@@ -942,7 +944,7 @@ impl<'a> MethodDef<'a> {
                                              struct_def,
                                              &format!("__self_{}",
                                                      i),
-                                             ast::MutImmutable);
+                                             ast::Mutability::Immutable);
             patterns.push(pat);
             raw_fields.push(ident_expr);
         }
@@ -1135,11 +1137,12 @@ impl<'a> MethodDef<'a> {
         let mut match_arms: Vec<ast::Arm> = variants.iter().enumerate()
             .map(|(index, variant)| {
                 let mk_self_pat = |cx: &mut ExtCtxt, self_arg_name: &str| {
-                    let (p, idents) = trait_.create_enum_variant_pattern(cx, type_ident,
-                                                                         &**variant,
-                                                                         self_arg_name,
-                                                                         ast::MutImmutable);
-                    (cx.pat(sp, ast::PatRegion(p, ast::MutImmutable)), idents)
+                    let (p, idents) = trait_.create_enum_variant_pattern(
+                        cx, type_ident,
+                        &**variant,
+                        self_arg_name,
+                        ast::Mutability::Immutable);
+                    (cx.pat(sp, ast::PatRegion(p, ast::Mutability::Immutable)), idents)
                 };
 
                 // A single arm has form (&VariantK, &VariantK, ...) => BodyK
diff --git a/src/libsyntax_ext/deriving/generic/ty.rs b/src/libsyntax_ext/deriving/generic/ty.rs
index e5b82fa1afc..a924cc06953 100644
--- a/src/libsyntax_ext/deriving/generic/ty.rs
+++ b/src/libsyntax_ext/deriving/generic/ty.rs
@@ -98,7 +98,7 @@ pub enum Ty<'a> {
 }
 
 pub fn borrowed_ptrty<'r>() -> PtrTy<'r> {
-    Borrowed(None, ast::MutImmutable)
+    Borrowed(None, ast::Mutability::Immutable)
 }
 pub fn borrowed<'r>(ty: Box<Ty<'r>>) -> Ty<'r> {
     Ptr(ty, borrowed_ptrty())
diff --git a/src/libsyntax_ext/deriving/hash.rs b/src/libsyntax_ext/deriving/hash.rs
index 6bd21f7c0e0..371ba732b48 100644
--- a/src/libsyntax_ext/deriving/hash.rs
+++ b/src/libsyntax_ext/deriving/hash.rs
@@ -11,7 +11,7 @@
 use deriving::generic::*;
 use deriving::generic::ty::*;
 
-use syntax::ast::{MetaItem, Expr, MutMutable};
+use syntax::ast::{MetaItem, Expr, Mutability};
 use syntax::codemap::Span;
 use syntax::ext::base::{ExtCtxt, Annotatable};
 use syntax::ext::build::AstBuilder;
@@ -43,7 +43,7 @@ pub fn expand_deriving_hash(cx: &mut ExtCtxt,
                                   vec![path_std!(cx, core::hash::Hasher)])],
                 },
                 explicit_self: borrowed_explicit_self(),
-                args: vec!(Ptr(Box::new(Literal(arg)), Borrowed(None, MutMutable))),
+                args: vec!(Ptr(Box::new(Literal(arg)), Borrowed(None, Mutability::Mutable))),
                 ret_ty: nil_ty(),
                 attributes: vec![],
                 is_unsafe: false,
diff --git a/src/libsyntax_ext/env.rs b/src/libsyntax_ext/env.rs
index f1dd6854a3a..63ec9cac073 100644
--- a/src/libsyntax_ext/env.rs
+++ b/src/libsyntax_ext/env.rs
@@ -42,7 +42,7 @@ pub fn expand_option_env<'cx>(cx: &'cx mut ExtCtxt, sp: Span, tts: &[ast::TokenT
                                                    Some(cx.lifetime(sp,
                                                         cx.ident_of(
                                                             "'static").name)),
-                                                   ast::MutImmutable)),
+                                                   ast::Mutability::Immutable)),
                                    Vec::new()))
       }
       Ok(s) => {
diff --git a/src/libsyntax_ext/format.rs b/src/libsyntax_ext/format.rs
index a5ad143f15b..4e24eb9f6d7 100644
--- a/src/libsyntax_ext/format.rs
+++ b/src/libsyntax_ext/format.rs
@@ -450,10 +450,10 @@ impl<'a, 'b> Context<'a, 'b> {
         let ty = ecx.ty_rptr(sp,
             ecx.ty(sp, ast::TyKind::Vec(piece_ty)),
             Some(ecx.lifetime(sp, special_idents::static_lifetime.name)),
-            ast::MutImmutable);
+            ast::Mutability::Immutable);
         let slice = ecx.expr_vec_slice(sp, pieces);
         // static instead of const to speed up codegen by not requiring this to be inlined
-        let st = ast::ItemKind::Static(ty, ast::MutImmutable, slice);
+        let st = ast::ItemKind::Static(ty, ast::Mutability::Immutable, slice);
 
         let name = ecx.ident_of(name);
         let item = ecx.item(sp, name, vec![], st);
@@ -480,7 +480,7 @@ impl<'a, 'b> Context<'a, 'b> {
                 self.fmtsp,
                 self.ecx.ty_ident(self.fmtsp, self.ecx.ident_of("str")),
                 Some(static_lifetime),
-                ast::MutImmutable);
+                ast::Mutability::Immutable);
         let pieces = Context::static_array(self.ecx,
                                            "__STATIC_FMTSTR",
                                            piece_ty,