diff --git a/src/user.zig b/src/user.zig
index 2bacbdb..a73c540 100644
--- a/src/user.zig
+++ b/src/user.zig
@@ -8,12 +8,13 @@ const assert = std.debug.assert;
 const mem = std.mem;
 const Allocator = mem.Allocator;
 const ArrayList = std.ArrayList;
+
 // Idx2ShellProto is a function prototype that, given a shell's index (in
 // global shell section), will return a shell string. Matches ShellReader.get.
 const Idx2ShellProto = fn (u6) []const u8;
 
 // User is a convenient public struct for record construction and
-// serialization. Iterator can help retrieve these records.
+// serialization.
 pub const User = struct {
     uid: u32,
     gid: u32,
@@ -23,7 +24,10 @@ pub const User = struct {
     shell: []const u8,
 
     // deep-clones a User record with a given Allocator.
-    pub fn clone(self: *const User, allocator: Allocator) Allocator.Error!User {
+    pub fn clone(
+        self: *const User,
+        allocator: Allocator,
+    ) Allocator.Error!User {
         const stringdata = try allocator.alloc(u8, self.strlen());
         const gecos_start = self.name.len;
         const home_start = gecos_start + self.gecos.len;
@@ -133,8 +137,9 @@ fn packedUser(immutable: bool) type {
         const Bytes = if (immutable) []const u8 else []u8;
         const InnerPointer = if (immutable) *const Inner else *Inner;
 
-        // PackedUser does not allocate; it re-interprets the "bytes" blob field.
-        // Both of those fields are pointers to "our representation" of that field.
+        // PackedUser does not allocate; it re-interprets the "bytes" blob
+        // field. Both of those fields are pointers to "our representation" of
+        // that field.
         inner: InnerPointer,
         userdata: Bytes,
 
@@ -190,9 +195,9 @@ fn packedUser(immutable: bool) type {
             };
         }
 
-        // packTo packs the User record and copies it to the given byte slice. The
-        // slice must have at least maxRecordSize() bytes available.
-        // The slice is passed as a pointer, so it can be mutated.
+        // packTo packs the User record and copies it to the given byte slice.
+        // The slice must have at least maxRecordSize() bytes available. The
+        // slice is passed as a pointer, so it can be mutated.
         const packErr = InvalidRecord || Allocator.Error;
         pub fn packTo(
             arr: *ArrayList(u8),
@@ -291,11 +296,8 @@ fn packedUser(immutable: bool) type {
             return idxFn(self.inner.shell_len_or_idx);
         }
 
+        // mutable only: this function will refuse to compile otherwise.
         pub fn setAdditionalGidsOffset(self: Self, new: u29) void {
-            // TODO(motiejus) how to not declare function for const PackedUser at all?
-            if (immutable) {
-                @compileError("this function is available only for mutable PackedUsers");
-            }
             self.inner.additional_gids_offset = new;
         }
     };
@@ -310,7 +312,11 @@ test "PackedUser internal and external alignment" {
     // cannot be converted from/to [@bitSizeOf(PackedUser)/8]u8;
     // asBytes/bytesAsValue use @sizeOf, which is larger. Now we are putting no
     // more than 1, but it probably could be higher.
-    try testing.expectEqual(8, @sizeOf(PackedUserConst.Inner) * 8 - @bitSizeOf(PackedUserConst.Inner));
+    try testing.expectEqual(
+        8,
+        @sizeOf(PackedUserConst.Inner) * 8 -
+            @bitSizeOf(PackedUserConst.Inner),
+    );
 }
 
 fn testShellIndex(shell: []const u8) ?u6 {
@@ -368,48 +374,45 @@ test "construct PackedUser section" {
     }
 
     var i: u29 = 0;
-    {
-        var it = PackedUserConst.iterator(buf.items, testShell);
-        while (it.next()) |user| : (i += 1) {
-            try testing.expectEqual(users[i].uid, user.uid());
-            try testing.expectEqual(users[i].gid, user.gid());
-            try testing.expectEqual(
-                @as(u29, std.math.maxInt(u29)),
-                user.additionalGidsOffset(),
-            );
-            try testing.expectEqualStrings(users[i].name, user.name());
-            try testing.expectEqualStrings(users[i].gecos, user.gecos());
-            try testing.expectEqualStrings(users[i].home, user.home());
-            try testing.expectEqualStrings(users[i].shell, user.shell(testShell));
-        }
-        try testing.expectEqual(users.len, i);
+    var it1 = PackedUserConst.iterator(buf.items, testShell);
+    while (it1.next()) |user| : (i += 1) {
+        try testing.expectEqual(users[i].uid, user.uid());
+        try testing.expectEqual(users[i].gid, user.gid());
+        try testing.expectEqual(
+            @as(u29, std.math.maxInt(u29)),
+            user.additionalGidsOffset(),
+        );
+        try testing.expectEqualStrings(users[i].name, user.name());
+        try testing.expectEqualStrings(users[i].gecos, user.gecos());
+        try testing.expectEqualStrings(users[i].home, user.home());
+        try testing.expectEqualStrings(users[i].shell, user.shell(testShell));
     }
+    try testing.expectEqual(users.len, i);
 
-    {
-        var it = PackedUserMut.iterator(buf.items, testShell);
-        i = 0;
-        while (it.next()) |user| : (i += 1) {
-            user.setAdditionalGidsOffset(i);
-        }
-        try testing.expectEqual(users.len, i);
+    var it2 = PackedUserMut.iterator(buf.items, testShell);
+    i = 0;
+    while (it2.next()) |user| : (i += 1) {
+        user.setAdditionalGidsOffset(i);
     }
+    try testing.expectEqual(users.len, i);
 
-    {
-        var it = PackedUserConst.iterator(buf.items, testShell);
-        i = 0;
-        while (it.next()) |user| : (i += 1) {
-            try testing.expectEqual(users[i].gid, user.gid());
-            try testing.expectEqual(i, user.additionalGidsOffset());
-            try testing.expectEqualStrings(users[i].name, user.name());
-        }
-        try testing.expectEqual(users.len, i);
+    var it3 = PackedUserConst.iterator(buf.items, testShell);
+    i = 0;
+    while (it3.next()) |user| : (i += 1) {
+        try testing.expectEqual(users[i].gid, user.gid());
+        try testing.expectEqual(i, user.additionalGidsOffset());
+        try testing.expectEqualStrings(users[i].name, user.name());
     }
+    try testing.expectEqual(users.len, i);
 }
 
 test "PackedUser.maxSize()" {
     // TODO(motiejus) try using a slice that points to an array in stack.
     // As of writing, I am getting a stack smashing error.
-    var buf = try ArrayList(u8).initCapacity(testing.allocator, PackedUserConst.maxSize());
+    var buf = try ArrayList(u8).initCapacity(
+        testing.allocator,
+        PackedUserConst.maxSize(),
+    );
     defer buf.deinit();
 
     const largeUser = User{