Use the same other error code convention as other WASi interfaces.

Relates to: #892

Author: badeend

proposals/sockets/wit-0.3.0-draft/ip-name-lookup.wit

@@ -5,13 +5,7 @@ interface ip-name-lookup {
 
     /// Lookup error codes.
     @since(version = 0.3.0-rc-2026-02-09)
-    enum error-code {
-        /// Unknown error
-        ///
-        /// This is an escape hatch for WASI implementations to handle failures
-        /// that can not be categorized under any of the other error codes.
-        unknown,
-
+    variant error-code {
         /// Access denied.
         ///
         /// POSIX equivalent: EACCES, EPERM
@@ -36,6 +30,11 @@ interface ip-name-lookup {
         ///
         /// POSIX equivalent: EAI_FAIL
         permanent-resolver-failure,
+
+        /// A catch-all for errors not captured by the existing variants.
+        /// Implementations can use this to extend the error type without
+        /// breaking existing code.
+        other(option<string>),
     }
 
     /// Resolve an internet host name to a list of IP addresses.

proposals/sockets/wit-0.3.0-draft/types.wit

@@ -15,13 +15,7 @@ interface types {
     ///
     /// See each individual API for what the POSIX equivalents are. They sometimes differ per API.
     @since(version = 0.3.0-rc-2026-02-09)
-    enum error-code {
-        /// Unknown error.
-        ///
-        /// This is an escape hatch for WASI implementations to handle failures
-        /// that can not be categorized under any of the other error codes.
-        unknown,
-
+    variant error-code {
         /// Access denied.
         ///
         /// POSIX equivalent: EACCES, EPERM
@@ -91,6 +85,11 @@ interface types {
         ///
         /// POSIX equivalent: EMSGSIZE
         datagram-too-large,
+
+        /// A catch-all for errors not captured by the existing variants.
+        /// Implementations can use this to extend the error type without
+        /// breaking existing code.
+        other(option<string>),
     }
 
     @since(version = 0.3.0-rc-2026-02-09)