js-runtime: Use the same tag for both func_js and func_zig

There is no technical different between the ways they are used. So its
better to merge them.

This commit further removes the internal ValueTag which worked under
Tag. On doing that tag type ``.ref`` has been renamed to ``.object``.

js-runtime/src/js-runtime.js

@@ -173,7 +173,6 @@ const zig = {
     switch (block.getU8(0)) {
       case 0:
       case 6:
-      case 7:
         return values[block.getU64(8)];
         break;
       case 1:

js-runtime/src/main.zig

@@ -24,25 +24,14 @@ const js = struct {
 };
 
 pub const Value = extern struct {
-    tag: ValueTag,
+    tag: Tag,
     val: extern union {
         ref: u64,
         num: f64,
         bool: bool,
     },
 
-    const ValueTag = enum(u8) {
+    pub const Tag = enum(u8) {
-        ref,
-        num,
-        bool,
-        str,
-        nulled,
-        undef,
-        func_js,
-        func_zig,
-    };
-
-    pub const Tag = enum {
         object,
         num,
         bool,
@@ -53,15 +42,7 @@ pub const Value = extern struct {
     };
 
     pub fn is(val: *const Value, comptime tag: Tag) bool {
-        return switch (tag) {
+        return val.tag == tag;
-            .object => val.tag == .object,
-            .num => val.tag == .num,
-            .bool => val.tag == .bool,
-            .str => val.tag == .str,
-            .nulled => val.tag == .nulled,
-            .undef => val.tag == .undef,
-            .func => val.tag == .func_js or val.tag == .func_zig,
-        };
     }
 
     pub fn view(val: *const Value, comptime tag: Tag) switch (tag) {
@@ -107,7 +88,7 @@ pub const Object = struct {
     }
 
     pub fn toValue(obj: *const Object) Value {
-        return .{ .tag = .ref, .val = .{ .ref = obj.ref } };
+        return .{ .tag = .object, .val = .{ .ref = obj.ref } };
     }
 
     pub fn get(obj: *const Object, prop: []const u8) Value {
@@ -153,7 +134,7 @@ pub const Function = struct {
     }
 
     pub fn toValue(func: *const Function) Value {
-        return .{ .tag = .func_zig, .val = .{ .ref = func.ref } };
+        return .{ .tag = .func, .val = .{ .ref = func.ref } };
     }
 
     pub fn construct(func: *const Function, args: []const Value) Value {