rework enums and unions and their relationship to each other

 * @enumTagName renamed to @tagName and it works on enums and
   union-enums
 * Remove the EnumTag type. Now there is only enum and union,
   and the tag type of a union is always an enum.
 * unions support specifying the tag enum type, and they support
   inferring an enum tag type.
 * Enums no longer support field types but they do support
   setting the tag values. Likewise union-enums when inferring
   an enum tag type support setting the tag values.
 * It is now an error for enums and unions to have 0 fields.
 * switch statements support union-enums

closes #618

2 files changed, 6 insertions, 6 deletions

diff --git a/std/os/child_process.zig b/std/os/child_process.zig
index 005d9772e4..3a4c9410c5 100644
--- a/std/os/child_process.zig
+++ b/std/os/child_process.zig
@@ -58,7 +58,7 @@ pub const ChildProcess = struct {
     err_pipe: if (is_windows) void else [2]i32,
     llnode: if (is_windows) void else LinkedList(&ChildProcess).Node,
 
-    pub const Term = enum {
+    pub const Term = union(enum) {
         Exited: i32,
         Signal: i32,
         Stopped: i32,
@@ -281,13 +281,13 @@ pub const ChildProcess = struct {
 
     fn statusToTerm(status: i32) -> Term {
         return if (posix.WIFEXITED(status)) {
-            Term.Exited { posix.WEXITSTATUS(status) }
+            Term { .Exited = posix.WEXITSTATUS(status) }
         } else if (posix.WIFSIGNALED(status)) {
-            Term.Signal { posix.WTERMSIG(status) }
+            Term { .Signal = posix.WTERMSIG(status) }
         } else if (posix.WIFSTOPPED(status)) {
-            Term.Stopped { posix.WSTOPSIG(status) }
+            Term { .Stopped = posix.WSTOPSIG(status) }
         } else {
-            Term.Unknown { status }
+            Term { .Unknown = status }
         };
     }
 
diff --git a/std/os/path.zig b/std/os/path.zig
index a372b5b077..3fd7b5e2db 100644
--- a/std/os/path.zig
+++ b/std/os/path.zig
@@ -1016,7 +1016,7 @@ pub fn real(allocator: &Allocator, pathname: []const u8) -> %[]u8 {
 
             return os.readLink(allocator, proc_path);
         },
-        else => @compileError("TODO implement os.path.real for " ++ @enumTagName(builtin.os)),
+        else => @compileError("TODO implement os.path.real for " ++ @tagName(builtin.os)),
     }
 }