Add a macro invocation to the type AST

Reapplied the changes from https://github.com/freebroccolo/rust/commit/dc64b731d7f66c2b43d5e5e8c721be7bd3b59540
to a clean branch of master

Author: jroesch

src/librustc_typeck/astconv.rs

@@ -1662,6 +1662,9 @@ pub fn ast_ty_to_ty<'tcx>(this: &AstConv<'tcx>,
             // handled specially and will not descend into this routine.
             this.ty_infer(None, None, None, ast_ty.span)
         }
+        ast::TyMac(_) => {
+            tcx.sess.span_bug(m.span, "unexpanded type macro found conversion")
+        }
     };
 
     tcx.ast_ty_to_ty_cache.borrow_mut().insert(ast_ty.id, typ);

src/librustdoc/clean/mod.rs

@@ -1611,6 +1611,9 @@ impl Clean<Type> for ast::Ty {
             TyTypeof(..) => {
                 panic!("Unimplemented type {:?}", self.node)
             },
+            TyMac(..) => {
+                cx.tcx().sess.span_bug(m.span, "unexpanded type macro found during cleaning")
+            }
         }
     }
 }

src/libsyntax/ast.rs

@@ -1471,6 +1471,8 @@ pub enum Ty_ {
     /// TyInfer means the type should be inferred instead of it having been
     /// specified. This can appear anywhere in a type.
     TyInfer,
+    // A macro in the type position.
+    TyMac(Mac)
 }
 
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]

src/libsyntax/fold.rs

@@ -429,6 +429,9 @@ pub fn noop_fold_ty<T: Folder>(t: P<Ty>, fld: &mut T) -> P<Ty> {
             TyPolyTraitRef(bounds) => {
                 TyPolyTraitRef(bounds.move_map(|b| fld.fold_ty_param_bound(b)))
             }
+            TyMac(mac) => {
+                TyMac(fld.fold_mac(mac))
+            }
         },
         span: fld.new_span(span)
     })

src/libsyntax/print/pprust.rs

@@ -734,6 +734,9 @@ impl<'a> State<'a> {
             ast::TyInfer => {
                 try!(word(&mut self.s, "_"));
             }
+            ast::TyMac(ref m) => {
+                try!(self.print_mac(m, token::Paren));
+            }
         }
         self.end()
     }

src/libsyntax/visit.rs

@@ -405,6 +405,9 @@ pub fn walk_ty<'v, V: Visitor<'v>>(visitor: &mut V, typ: &'v Ty) {
             visitor.visit_expr(&**expression)
         }
         TyInfer => {}
+        TyMac(ref mac) => {
+            visitor.visit_mac(mac)
+        }
     }
 }