From 6bd07f8c2b92eaa522e406b12eba19eaf0f1ce0e Mon Sep 17 00:00:00 2001
From: Matthew Nibecker <hello@mattnibecker.com>
Date: Fri, 22 May 2026 12:29:51 -0700
Subject: [PATCH] vam.Dot expr: Fix fusion unions

---
 runtime/vam/expr/dot.go      | 2 ++
 runtime/ztests/expr/dot.yaml | 4 ++++
 2 files changed, 6 insertions(+)

diff --git a/runtime/vam/expr/dot.go b/runtime/vam/expr/dot.go
index 067d9ab3a..b4c9d5b98 100644
--- a/runtime/vam/expr/dot.go
+++ b/runtime/vam/expr/dot.go
@@ -66,6 +66,8 @@ func (d *DotExpr) eval(vecs ...vector.Any) vector.Any {
 	case *vector.Map:
 		keyVec := vector.NewConstString(d.field, val.Len())
 		return indexMap(d.sctx, val, keyVec)
+	case *vector.Union:
+		return vector.Apply(false, d.eval, val.Dynamic())
 	case *vector.View:
 		return vector.Pick(d.eval(val.Any), val.Index)
 	default:
diff --git a/runtime/ztests/expr/dot.yaml b/runtime/ztests/expr/dot.yaml
index b61c8de18..341182944 100644
--- a/runtime/ztests/expr/dot.yaml
+++ b/runtime/ztests/expr/dot.yaml
@@ -5,6 +5,8 @@ input: |
   {a:{b:1::(int64|string)}}
   {a:{b:1}::(int64|{b:int64})}
   {a:{b:1}}::(int64|{a:{b:int64}})
+  {a:fusion({b:1}::(null|{b:int64}),<{b:int64}>)}
+  {a:fusion(null::(null|{b:int64}),<null>)}
   {a:1}
   {}
   null
@@ -14,6 +16,8 @@ output: |
   1::(int64|string)
   1
   1
+  1
+  error("missing")
   error("missing")
   error("missing")
   error("missing")