From f710419ead4c756261fdb67526936721a1c70a26 Mon Sep 17 00:00:00 2001
From: Emery Hemingway <ehmry@posteo.net>
Date: Sat, 11 Dec 2021 18:36:31 +0000
Subject: [PATCH] Generate patterns from ref types

---
 src/syndicate/patterns.nim | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/src/syndicate/patterns.nim b/src/syndicate/patterns.nim
index 0d52557..14891e9 100644
--- a/src/syndicate/patterns.nim
+++ b/src/syndicate/patterns.nim
@@ -1,7 +1,7 @@
 # SPDX-FileCopyrightText: ☭ 2021 Emery Hemingway
 # SPDX-License-Identifier: Unlicense
 
-import std/[macros, tables]
+import std/[macros, tables, typetraits]
 
 import preserves
 import ./protocols/dataspacePatterns
@@ -29,13 +29,11 @@ proc `?`*(d: DCompound): Pattern =
 proc `?`*(s: string): Pattern =
   ?DLit(value: toPreserve(s, Ref))
 
-proc arity(T: typedesc): int =
-  var t: T # a hack to iterate the fields of a non-existent instance
-  for _ in fields(t): inc result
+proc drop*(): Pattern = Pattern(orKind: PatternKind.DDiscard)
+proc grab*(): Pattern = ?DBind(pattern: drop())
 
-proc `?_`*(): Pattern = Pattern(orKind: PatternKind.DDiscard)
-
-proc `?*`*(): Pattern = ?DBind(pattern: `?_`())
+proc `?_`*(): Pattern = drop()
+proc `?*`*(): Pattern = grab()
 
 proc `?`*(T: typedesc; bindings: openArray[(int, Pattern)]): Pattern =
   ## Pattern constructor operator.
@@ -44,8 +42,10 @@ proc `?`*(T: typedesc; bindings: openArray[(int, Pattern)]): Pattern =
     result = ?DCompound(
       orKind: DCompoundKind.rec,
       rec: DCompoundRec(
-        ctor: CRec(label: label, arity: T.arity),
+        ctor: CRec(label: label, arity: bindings.len),
         members: toTable bindings))
+  elif T is ref:
+    `?`(pointerBase(T), bindings)
   else:
     {.error: "no custom pragma on " & $T.}