Allow zero-sized fields in extern structs (#16404)

This change allows the following types to appear in extern structs:
* Zero-bit integers
* void
* zero-sized structs and packed structs
* enums with zero-bit backing integers
* arrays of any length with zero-size elements

1 files changed, 21 insertions, 0 deletions

diff --git a/test/behavior/extern_struct_zero_size_fields.zig b/test/behavior/extern_struct_zero_size_fields.zig
new file mode 100644
index 0000000000..1b13532f11
--- /dev/null
+++ b/test/behavior/extern_struct_zero_size_fields.zig
@@ -0,0 +1,21 @@
+const E = enum(u0) {
+    the_only_possible_value,
+};
+
+const S = struct {};
+
+const T = extern struct {
+    foo: u0 = 0,
+    bar: void = {},
+    baz: struct {} = .{},
+    ayy: E = .the_only_possible_value,
+    arr: [0]u0 = .{},
+    matey: [128]void = [_]void{{}} ** 128,
+    running_out_of_ideas: packed struct {} = .{},
+    one_more: [256]S = [_]S{.{}} ** 256,
+};
+
+test {
+    var t: T = .{};
+    _ = t;
+}