Start implementation of RFC 1216 (make ! a type)

Add `TyKind::Empty` and fix resulting build errors.

4 files changed, 8 insertions, 0 deletions

diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index 3f929e6d23a..6ba5eccc5cf 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -1348,6 +1348,7 @@ pub struct BareFnTy {
 /// The different kinds of types recognized by the compiler
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub enum TyKind {
+    /// A variable-length array (`[T]`)
     Vec(P<Ty>),
     /// A fixed length array (`[T; n]`)
     FixedLengthVec(P<Ty>, P<Expr>),
@@ -1357,6 +1358,8 @@ pub enum TyKind {
     Rptr(Option<Lifetime>, MutTy),
     /// A bare function (e.g. `fn(usize) -> bool`)
     BareFn(P<BareFnTy>),
+    /// The empty type (`!`)
+    Empty,
     /// A tuple (`(A, B, C, D,...)`)
     Tup(Vec<P<Ty>> ),
     /// A path (`module::module::...::Type`), optionally
diff --git a/src/libsyntax/fold.rs b/src/libsyntax/fold.rs
index afc990f498e..47addd8aba5 100644
--- a/src/libsyntax/fold.rs
+++ b/src/libsyntax/fold.rs
@@ -373,6 +373,7 @@ pub fn noop_fold_ty<T: Folder>(t: P<Ty>, fld: &mut T) -> P<Ty> {
                     decl: fld.fold_fn_decl(decl)
                 }))
             }
+            TyKind::Empty => node,
             TyKind::Tup(tys) => TyKind::Tup(tys.move_map(|ty| fld.fold_ty(ty))),
             TyKind::Paren(ty) => TyKind::Paren(fld.fold_ty(ty)),
             TyKind::Path(qself, path) => {
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index 62e55eb78b7..6214dc5301b 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -976,6 +976,9 @@ impl<'a> State<'a> {
                 try!(self.print_opt_lifetime(lifetime));
                 try!(self.print_mt(mt));
             }
+            ast::TyKind::Empty => {
+                word(&mut self.s, "!")?;
+            },
             ast::TyKind::Tup(ref elts) => {
                 try!(self.popen());
                 try!(self.commasep(Inconsistent, &elts[..],
diff --git a/src/libsyntax/visit.rs b/src/libsyntax/visit.rs
index 6d3cdbdc6da..1d40e3e395e 100644
--- a/src/libsyntax/visit.rs
+++ b/src/libsyntax/visit.rs
@@ -319,6 +319,7 @@ pub fn walk_ty<V: Visitor>(visitor: &mut V, typ: &Ty) {
             walk_list!(visitor, visit_lifetime, opt_lifetime);
             visitor.visit_ty(&mutable_type.ty)
         }
+        TyKind::Empty => {},
         TyKind::Tup(ref tuple_element_types) => {
             walk_list!(visitor, visit_ty, tuple_element_types);
         }