From 8b8e57c670132d615f2b5bbf69acf1658c083b12 Mon Sep 17 00:00:00 2001
From: Erik Arvstedt <erik.arvstedt@gmail.com>
Date: Wed, 4 May 2022 20:01:48 +0200
Subject: [PATCH 1/2] std.meta.TrailerFlags: include in std tests

Previously, TrailerFlags was unreferenced in std,
so its tests were never run.

Also, fix the use of `default_value` whose type was changed in
f4a249325e8e3741a6294462ae37a79cb9089c56 (#10766).
---
 lib/std/meta.zig               | 4 ++++
 lib/std/meta/trailer_flags.zig | 5 +----
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/lib/std/meta.zig b/lib/std/meta.zig
index e6ce746f19..0de51bfa68 100644
--- a/lib/std/meta.zig
+++ b/lib/std/meta.zig
@@ -10,6 +10,10 @@ pub const TrailerFlags = @import("meta/trailer_flags.zig").TrailerFlags;
 
 const Type = std.builtin.Type;
 
+test "std.meta.TrailerFlags" {
+    _ = TrailerFlags;
+}
+
 pub fn tagName(v: anytype) []const u8 {
     const T = @TypeOf(v);
     switch (@typeInfo(T)) {
diff --git a/lib/std/meta/trailer_flags.zig b/lib/std/meta/trailer_flags.zig
index a128564708..e4288692b1 100644
--- a/lib/std/meta/trailer_flags.zig
+++ b/lib/std/meta/trailer_flags.zig
@@ -24,10 +24,7 @@ pub fn TrailerFlags(comptime Fields: type) type {
                 fields[i] = Type.StructField{
                     .name = struct_field.name,
                     .field_type = ?struct_field.field_type,
-                    .default_value = @as(
-                        ??struct_field.field_type,
-                        @as(?struct_field.field_type, null),
-                    ),
+                    .default_value = &@as(?struct_field.field_type, null),
                     .is_comptime = false,
                     .alignment = @alignOf(?struct_field.field_type),
                 };

From e5b07d8187c8e36c7fad4d190d9eac604018ce3b Mon Sep 17 00:00:00 2001
From: Erik Arvstedt <erik.arvstedt@gmail.com>
Date: Wed, 4 May 2022 20:01:49 +0200
Subject: [PATCH 2/2] std.meta.TrailerFlags: improve init type

---
 lib/std/meta/trailer_flags.zig | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/lib/std/meta/trailer_flags.zig b/lib/std/meta/trailer_flags.zig
index e4288692b1..212a47bc29 100644
--- a/lib/std/meta/trailer_flags.zig
+++ b/lib/std/meta/trailer_flags.zig
@@ -18,7 +18,8 @@ pub fn TrailerFlags(comptime Fields: type) type {
 
         pub const FieldEnum = std.meta.FieldEnum(Fields);
 
-        pub const InitStruct = blk: {
+        pub const ActiveFields = std.enums.EnumFieldStruct(FieldEnum, bool, false);
+        pub const FieldValues = blk: {
             comptime var fields: [bit_count]Type.StructField = undefined;
             inline for (@typeInfo(Fields).Struct.fields) |struct_field, i| {
                 fields[i] = Type.StructField{
@@ -57,19 +58,18 @@ pub fn TrailerFlags(comptime Fields: type) type {
             self.bits |= 1 << field_index;
         }
 
-        /// `fields` is a struct with each field set to an optional value.
-        /// Only the non-null bits are observed and are used to set the flag bits.
-        pub fn init(fields: InitStruct) Self {
+        /// `fields` is a boolean struct where each active field is set to `true`
+        pub fn init(fields: ActiveFields) Self {
             var self: Self = .{ .bits = 0 };
             inline for (@typeInfo(Fields).Struct.fields) |field, i| {
-                if (@field(fields, field.name)) |_|
+                if (@field(fields, field.name))
                     self.bits |= 1 << i;
             }
             return self;
         }
 
-        /// `fields` is a struct with each field set to an optional value (same as `init`).
-        pub fn setMany(self: Self, p: [*]align(@alignOf(Fields)) u8, fields: InitStruct) void {
+        /// `fields` is a struct with each field set to an optional value
+        pub fn setMany(self: Self, p: [*]align(@alignOf(Fields)) u8, fields: FieldValues) void {
             inline for (@typeInfo(Fields).Struct.fields) |field, i| {
                 if (@field(fields, field.name)) |value|
                     self.set(p, @intToEnum(FieldEnum, i), value);
@@ -142,7 +142,7 @@ test "TrailerFlags" {
 
     var flags = Flags.init(.{
         .b = true,
-        .c = 1234,
+        .c = true,
     });
     const slice = try testing.allocator.allocAdvanced(u8, 8, flags.sizeInBytes(), .exact);
     defer testing.allocator.free(slice);