From efb7148a4574c608b21359fcbf2edf06afdb5e0c Mon Sep 17 00:00:00 2001
From: Andrew Kelley <andrew@ziglang.org>
Date: Tue, 28 Dec 2021 23:10:48 -0700
Subject: Sema: more union fixes

 * `Module.Union.getLayout`: fixes to support components of the union
   being 0 bits.
 * Implement `@typeInfo` for unions.
 * Add missing calls to `resolveTypeFields`.
 * Fix explicitly-provided union tag types passing a `Zir.Inst.Ref`
   where an `Air.Inst.Ref` was expected. We don't have any type safety
   for this; these typess are aliases.
 * Fix explicitly-provided `union(enum)` tag Values allocated to the
   wrong arena.
---
 src/type.zig | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

(limited to 'src/type.zig')

diff --git a/src/type.zig b/src/type.zig
index feea1fe2c1..5bcf310fc4 100644
--- a/src/type.zig
+++ b/src/type.zig
@@ -2868,7 +2868,11 @@ pub const Type = extern union {
     /// Otherwise, returns `null`.
     pub fn unionTagType(ty: Type) ?Type {
         return switch (ty.tag()) {
-            .union_tagged => ty.castTag(.union_tagged).?.data.tag_ty,
+            .union_tagged => {
+                const union_obj = ty.castTag(.union_tagged).?.data;
+                assert(union_obj.haveFieldTypes());
+                return union_obj.tag_ty;
+            },
 
             .atomic_order,
             .atomic_rmw_op,
-- 
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