stage2: fix AstGen for some struct syntaxes

 * AstGen: fix not emitting `struct_init_empty` when an explicit type is
   present in struct initialization syntax.
 * AstGen: these two syntaxes now lower to identical ZIR:
   - `var a = A{ .b = c };`
   - `var a = @as(A, .{ .b = c });`
 * Zir: clarify `auto_enum_tag` in the doc comments.
 * LLVM Backend: fix lowering of function return types when the type has
   0 bits.

1 files changed, 2 insertions, 1 deletions

diff --git a/test/behavior.zig b/test/behavior.zig
index 7fbba99a8c..78f3651b01 100644
--- a/test/behavior.zig
+++ b/test/behavior.zig
@@ -13,6 +13,7 @@ test {
     _ = @import("behavior/atomics.zig");
     _ = @import("behavior/sizeof_and_typeof.zig");
     _ = @import("behavior/translate_c_macros.zig");
+    _ = @import("behavior/struct.zig");
     _ = @import("behavior/union.zig");
     _ = @import("behavior/widening.zig");
 
@@ -135,7 +136,7 @@ test {
         _ = @import("behavior/sizeof_and_typeof_stage1.zig");
         _ = @import("behavior/slice.zig");
         _ = @import("behavior/slice_sentinel_comptime.zig");
-        _ = @import("behavior/struct.zig");
+        _ = @import("behavior/struct_stage1.zig");
         _ = @import("behavior/struct_contains_null_ptr_itself.zig");
         _ = @import("behavior/struct_contains_slice_of_itself.zig");
         _ = @import("behavior/switch.zig");