From a7b3082ba0d07c66d2ec19304ffe993d77f714b7 Mon Sep 17 00:00:00 2001
From: John Schmidt <john.schmidt.h@gmail.com>
Date: Sat, 12 Feb 2022 16:57:52 +0100
Subject: Implement `type.bitSize` for unions

---
 src/type.zig | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

(limited to 'src/type.zig')

diff --git a/src/type.zig b/src/type.zig
index d5b8e6f5b3..6b7214888d 100644
--- a/src/type.zig
+++ b/src/type.zig
@@ -3251,8 +3251,20 @@ pub const Type = extern union {
                 const int_tag_ty = ty.intTagType(&buffer);
                 return int_tag_ty.bitSize(target);
             },
+
             .@"union", .union_tagged => {
-                @panic("TODO bitSize unions");
+                const union_obj = ty.cast(Payload.Union).?.data;
+
+                const fields = union_obj.fields;
+                if (fields.count() == 0) return 0;
+
+                assert(union_obj.haveFieldTypes());
+
+                var size: u64 = 0;
+                for (fields.values()) |field| {
+                    size = @maximum(size, field.ty.bitSize(target));
+                }
+                return size;
             },
 
             .vector => {
-- 
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