auto merge of #5578 : erickt/rust/incoming, r=jbclements,erickt

Hey folks,

This patch series does some work on the json decoder, specifically with auto decoding of enums. Previously, we would take this code:

```
enum A {
    B,
    C(~str, uint)
}
```

and would encode a value of this enum to either `["B", []]` or `["C", ["D", 123]]`. I've changed this to `"B"` or `["C", "D", 123]`. This matches the style of the O'Caml json library [json-wheel](http://mjambon.com/json-wheel.html). I've added tests to make sure all this work.

In order to make this change, I added passing a `&[&str]` vec to `Decode::emit_enum_variant` so the json decoder can convert the name of a variant into it's position. I also changed the impl of `Encodable` for `Option<T>` to have the right upper casing.

I also did some work on the parser, which allows for `fn foo<T: ::cmp::Eq>() { ... }` statements (#5572), fixed the pretty printer properly expanding `debug!("...")` expressions, and removed `ast::expr_vstore_fixed`, which doesn't appear to be used anymore.

Author: bors

src/librustc/middle/astencode.rs

@@ -681,6 +681,7 @@ impl vtable_decoder_helpers for reader::Decoder {
         @self.read_to_vec(|| self.read_vtable_origin(xcx) )
     }
 
+    #[cfg(stage0)]
     fn read_vtable_origin(&self, xcx: @ExtendedDecodeContext)
         -> typeck::vtable_origin {
         do self.read_enum(~"vtable_origin") {
@@ -715,6 +716,44 @@ impl vtable_decoder_helpers for reader::Decoder {
             }
         }
     }
+
+    #[cfg(stage1)]
+    #[cfg(stage2)]
+    #[cfg(stage3)]
+    fn read_vtable_origin(&self, xcx: @ExtendedDecodeContext)
+        -> typeck::vtable_origin {
+        do self.read_enum("vtable_origin") {
+            do self.read_enum_variant(["vtable_static", "vtable_param"]) |i| {
+                match i {
+                  0 => {
+                    typeck::vtable_static(
+                        do self.read_enum_variant_arg(0u) {
+                            self.read_def_id(xcx)
+                        },
+                        do self.read_enum_variant_arg(1u) {
+                            self.read_tys(xcx)
+                        },
+                        do self.read_enum_variant_arg(2u) {
+                            self.read_vtable_res(xcx)
+                        }
+                    )
+                  }
+                  1 => {
+                    typeck::vtable_param(
+                        do self.read_enum_variant_arg(0u) {
+                            self.read_uint()
+                        },
+                        do self.read_enum_variant_arg(1u) {
+                            self.read_uint()
+                        }
+                    )
+                  }
+                  // hard to avoid - user input
+                  _ => fail!(~"bad enum variant")
+                }
+            }
+        }
+    }
 }
 
 // ______________________________________________________________________

src/librustc/middle/check_const.rs

@@ -156,7 +156,6 @@ pub fn check_expr(sess: Session,
           expr_paren(e) => { check_expr(sess, def_map, method_map,
                                          tcx, e, is_const, v); }
           expr_vstore(_, expr_vstore_slice) |
-          expr_vstore(_, expr_vstore_fixed(_)) |
           expr_vec(_, m_imm) |
           expr_addr_of(m_imm, _) |
           expr_field(*) |

src/librustc/middle/const_eval.rs

@@ -110,7 +110,6 @@ pub fn classify(e: @expr,
 
               ast::expr_vstore(e, vstore) => {
                   match vstore {
-                      ast::expr_vstore_fixed(_) |
                       ast::expr_vstore_slice => classify(e, tcx),
                       ast::expr_vstore_uniq |
                       ast::expr_vstore_box |

src/librustc/middle/liveness.rs

@@ -1290,7 +1290,7 @@ pub impl Liveness {
             self.propagate_through_expr(l, ln)
           }
 
-          expr_log(_, l, r) |
+          expr_log(l, r) |
           expr_index(l, r) |
           expr_binary(_, l, r) => {
             self.propagate_through_exprs(~[l, r], succ)

src/librustc/middle/moves.rs

@@ -567,7 +567,7 @@ pub impl VisitContext {
                 self.consume_block(blk, visitor);
             }
 
-            expr_log(_, a_expr, b_expr) => {
+            expr_log(a_expr, b_expr) => {
                 self.consume_expr(a_expr, visitor);
                 self.use_expr(b_expr, Read, visitor);
             }

src/librustc/middle/trans/consts.rs

@@ -466,9 +466,6 @@ fn const_expr_unadjusted(cx: @CrateContext, e: @ast::expr) -> ValueRef {
             let (v, _, _) = const_vec(cx, e, *es);
             v
           }
-          ast::expr_vstore(e, ast::expr_vstore_fixed(_)) => {
-            const_expr(cx, e)
-          }
           ast::expr_vstore(sub, ast::expr_vstore_slice) => {
             match sub.node {
               ast::expr_lit(ref lit) => {

src/librustc/middle/trans/expr.rs

@@ -496,7 +496,7 @@ fn trans_rvalue_stmt_unadjusted(bcx: block, expr: @ast::expr) -> block {
         ast::expr_ret(ex) => {
             return controlflow::trans_ret(bcx, ex);
         }
-        ast::expr_log(_, lvl, a) => {
+        ast::expr_log(lvl, a) => {
             return controlflow::trans_log(expr, lvl, bcx, a);
         }
         ast::expr_while(cond, ref body) => {
@@ -703,9 +703,6 @@ fn trans_rvalue_dps_unadjusted(bcx: block, expr: @ast::expr,
         ast::expr_vstore(contents, ast::expr_vstore_mut_slice) => {
             return tvec::trans_slice_vstore(bcx, expr, contents, dest);
         }
-        ast::expr_vstore(contents, ast::expr_vstore_fixed(_)) => {
-            return tvec::trans_fixed_vstore(bcx, expr, contents, dest);
-        }
         ast::expr_vec(*) | ast::expr_repeat(*) => {
             return tvec::trans_fixed_vstore(bcx, expr, expr, dest);
         }

src/librustc/middle/trans/type_use.rs

@@ -329,7 +329,7 @@ pub fn mark_for_expr(cx: Context, e: @expr) {
         type_needs(cx, use_repr, ty::type_autoderef(cx.ccx.tcx, base_ty));
         mark_for_method_call(cx, e.id, e.callee_id);
       }
-      expr_log(_, _, val) => {
+      expr_log(_, val) => {
         node_type_needs(cx, use_tydesc, val.id);
       }
       expr_call(f, _, _) => {

src/librustc/middle/ty.rs

@@ -3114,7 +3114,6 @@ pub fn expr_kind(tcx: ctxt,
         ast::expr_lit(@codemap::spanned {node: lit_str(_), _}) |
         ast::expr_vstore(_, ast::expr_vstore_slice) |
         ast::expr_vstore(_, ast::expr_vstore_mut_slice) |
-        ast::expr_vstore(_, ast::expr_vstore_fixed(_)) |
         ast::expr_vec(*) => {
             RvalueDpsExpr
         }

src/librustc/middle/typeck/check/mod.rs

@@ -2366,7 +2366,7 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
         }
         fcx.write_bot(id);
       }
-      ast::expr_log(_, lv, e) => {
+      ast::expr_log(lv, e) => {
         check_expr_has_type(fcx, lv,
                                   ty::mk_mach_uint(tcx, ast::ty_u32));
 
@@ -3301,14 +3301,6 @@ pub fn ast_expr_vstore_to_vstore(fcx: @mut FnCtxt,
                                  v: ast::expr_vstore)
                               -> ty::vstore {
     match v {
-        ast::expr_vstore_fixed(None) => ty::vstore_fixed(n),
-        ast::expr_vstore_fixed(Some(u)) => {
-            if n != u {
-                let s = fmt!("fixed-size sequence mismatch: %u vs. %u",u, n);
-                fcx.ccx.tcx.sess.span_err(e.span,s);
-            }
-            ty::vstore_fixed(u)
-        }
         ast::expr_vstore_uniq => ty::vstore_uniq,
         ast::expr_vstore_box | ast::expr_vstore_mut_box => ty::vstore_box,
         ast::expr_vstore_slice | ast::expr_vstore_mut_slice => {