rustc: For one-tuples, make parsing and printing the type work

and add a test to reflect-visit-data

src/libcore/to_str.rs

@@ -43,6 +43,8 @@ impl ToStr for @str {
     pure fn to_str(&self) -> ~str { ::str::from_slice(*self) }
 }
 
+// FIXME #4898: impl for one-tuples
+
 impl<A: ToStr, B: ToStr> ToStr for (A, B) {
     #[inline(always)]
     pure fn to_str(&self) -> ~str {

src/libcore/tuple.rs

@@ -111,6 +111,8 @@ impl<A: Copy, B: Copy> ExtendedTupleOps<A,B> for (~[A], ~[B]) {
     }
 }
 
+// FIXME #4898: impl for one-tuples
+
 #[cfg(notest)]
 impl<A: Eq, B: Eq> Eq for (A, B) {
     #[inline(always)]

src/libsyntax/parse/parser.rs

@@ -576,12 +576,21 @@ pub impl Parser {
                 self.bump();
                 ty_nil
             } else {
+                // (t) is a parenthesized ty
+                // (t,) is the type of a tuple with only one field,
+                // of type t
                 let mut ts = ~[self.parse_ty(false)];
+                let mut one_tuple = false;
                 while self.token == token::COMMA {
                     self.bump();
-                    ts.push(self.parse_ty(false));
+                    if self.token != token::RPAREN {
+                        ts.push(self.parse_ty(false));
+                    }
+                    else {
+                        one_tuple = true;
+                    }
                 }
-                let t = if vec::len(ts) == 1u { ts[0].node }
+                let t = if ts.len() == 1 && !one_tuple { ts[0].node }
                 else { ty_tup(ts) };
                 self.expect(token::RPAREN);
                 t

src/libsyntax/print/pprust.rs

@@ -414,6 +414,9 @@ pub fn print_type_ex(s: @ps, &&ty: @ast::Ty, print_colons: bool) {
       ast::ty_tup(elts) => {
         popen(s);
         commasep(s, inconsistent, elts, print_type);
+        if elts.len() == 1 {
+            word(s.s, ~",");
+        }
         pclose(s);
       }
       ast::ty_bare_fn(f) => {

src/test/run-pass/one-tuple.rs

@@ -16,5 +16,9 @@ fn main() {
             assert x == 'c';
         }
     }
+    // test the 1-tuple type too
+    let x: (char,) = ('d',);
+    let (y,) = x;
+    assert y == 'd';
 }
 

src/test/run-pass/reflect-visit-data.rs

@@ -636,11 +636,12 @@ struct Triple { x: int, y: int, z: int }
 
 pub fn main() {
     unsafe {
-        let r = (1,2,3,true,false, Triple {x:5,y:4,z:3});
+        let r = (1,2,3,true,false, Triple {x:5,y:4,z:3}, (12,));
         let p = ptr::addr_of(&r) as *c_void;
         let u = my_visitor(@Stuff {mut ptr1: p,
                              mut ptr2: p,
-                             mut vals: ~[]});
+                             mut vals: ~[]
+                                  });
         let v = ptr_visit_adaptor(Inner {inner: u});
         let td = get_tydesc_for(r);
         unsafe { error!("tydesc sz: %u, align: %u",
@@ -653,7 +654,7 @@ pub fn main() {
         }
         error!("%?", copy u.vals);
         assert u.vals == ~[
-            ~"1", ~"2", ~"3", ~"true", ~"false", ~"5", ~"4", ~"3"
+            ~"1", ~"2", ~"3", ~"true", ~"false", ~"5", ~"4", ~"3", ~"12"
         ];
     }
  }