From 783a30dd7962d53ef6b5a0852473b915d7d0afdc Mon Sep 17 00:00:00 2001
From: Ryan P <r.pridgeon@f5.com>
Date: Fri, 26 Jun 2026 12:24:59 -0400
Subject: [PATCH] allow type aliasing of DefinedType

---
 crates/wac-graph/src/graph.rs                     |  9 ++++++++-
 crates/wac-parser/tests/encoding/types.wac        |  7 +++++++
 crates/wac-parser/tests/encoding/types.wac.result | 11 +++++++++++
 3 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/crates/wac-graph/src/graph.rs b/crates/wac-graph/src/graph.rs
index ace9cba..719ee26 100644
--- a/crates/wac-graph/src/graph.rs
+++ b/crates/wac-graph/src/graph.rs
@@ -1668,7 +1668,14 @@ impl<'a> CompositionGraphEncoder<'a> {
                         if let DefinedType::Alias(aliased @ ValueType::Defined(_)) =
                             &self.0.types()[id]
                         {
-                            (ty, state.current.type_indexes[&Type::Value(*aliased)])
+                            if let Some(&index) =
+                                // check if aliased had previously been exported
+                                state.current.type_indexes.get(&Type::Value(*aliased))
+                            {
+                                (ty, index)
+                            } else {
+                                (ty, encoder.ty(state, ty, None))
+                            }
                         } else {
                             (ty, encoder.ty(state, ty, None))
                         }
diff --git a/crates/wac-parser/tests/encoding/types.wac b/crates/wac-parser/tests/encoding/types.wac
index 5a67bce..45c79f3 100644
--- a/crates/wac-parser/tests/encoding/types.wac
+++ b/crates/wac-parser/tests/encoding/types.wac
@@ -118,3 +118,10 @@ type m2 = m;
 type o2 = o;
 type p2 = p;
 type q2 = q;
+
+// Test encoding of aliases to inline-created defined types
+type list-alias = list<u8>;
+type option-alias = option<string>;
+type result-alias = result<u32, string>;
+type tuple-alias = tuple<u8, u16>;
+type nested-list-alias = list<list<u8>>;
diff --git a/crates/wac-parser/tests/encoding/types.wac.result b/crates/wac-parser/tests/encoding/types.wac.result
index a4c72ef..6d91ecc 100644
--- a/crates/wac-parser/tests/encoding/types.wac.result
+++ b/crates/wac-parser/tests/encoding/types.wac.result
@@ -170,6 +170,17 @@
   (export $o2 (;58;) "o2" (type $o))
   (export $p2 (;59;) "p2" (type $p))
   (export $q2 (;60;) "q2" (type $q))
+  (type (;61;) (list u8))
+  (export $list-alias (;62;) "list-alias" (type 61))
+  (type (;63;) (option string))
+  (export $option-alias (;64;) "option-alias" (type 63))
+  (type (;65;) (result u32 (error string)))
+  (export $result-alias (;66;) "result-alias" (type 65))
+  (type (;67;) (tuple u8 u16))
+  (export $tuple-alias (;68;) "tuple-alias" (type 67))
+  (type (;69;) (list u8))
+  (type (;70;) (list 69))
+  (export $nested-list-alias (;71;) "nested-list-alias" (type 70))
   (@producers
     (processed-by "wac-parser" "0.10.1")
   )