Unpack.nil: allow to call outside of comptime

Author: thislight

src/io.zig

@@ -193,8 +193,8 @@ pub const UnpackReader = struct {
 
     pub const ConvertError = fmt.Unpack.ConvertError;
 
-    pub fn nil(self: *UnpackReader, _: anytype, header: fmt.Header) !@TypeOf(null) {
-        return self.unpack.nil(header);
+    pub fn nil(self: *UnpackReader, _: anytype, T: type, header: fmt.Header) !T {
+        return self.unpack.nil(T, header);
     }
 
     pub fn @"bool"(self: *UnpackReader, _: anytype, header: fmt.Header) !bool {

src/rewriter.zig

@@ -10,7 +10,10 @@ fn rewriteValue(
     h: zigpak.Header,
 ) !void {
     switch (h.type.family()) {
-        .nil => _ = try zigpak.io.writeNil(writer),
+        .nil => {
+            _ = try values.nil(reader, ?*anyopaque, h);
+            _ = try zigpak.io.writeNil(writer);
+        },
         .bool => _ = try zigpak.io.writeBool(writer, try values.bool(reader, h)),
         .int => _ = try zigpak.io.writeIntSm(writer, try values.int(reader, i64, h)),
         .uint => _ = try zigpak.io.writeIntSm(writer, try values.int(reader, u64, h)),

src/root.zig

@@ -826,9 +826,8 @@ pub const Unpack = struct {
 
     /// Consumes the current value as the null.
     ///
-    /// Note that the result must be peer resolved to a type
-    /// with valid representation, like `?*opaque {}`.
-    pub fn nil(_: *Unpack, header: Header) ConvertError!@TypeOf(null) {
+    /// The `T` must be optional types.
+    pub fn nil(_: *Unpack, T: type, header: Header) ConvertError!T {
         if (header.type == .nil) {
             return null;
         }