From c995e65ff25ff6bdaed7f22c253955ad5398a253 Mon Sep 17 00:00:00 2001
From: Kris Kowal <kriskowal@kriskowal.com>
Date: Wed, 29 Apr 2026 23:43:56 +0000
Subject: [PATCH] fix(patterns): handle copyBag in getRankCover kindMatcher
 (#3052)

The match:kind helper's getRankCover only mapped copySet and copyMap to
the 'tagged' pass style, leaving copyBag to fall through to the default
branch where getPassStyleCover('copyBag') threw a TypeError because
'copyBag' is not a known PassStyle. Add copyBag alongside copySet and
copyMap so all three tagged-encoded kinds share the same rank cover.
---
 .../patterns/src/patterns/patternMatchers.js  |  1 +
 packages/patterns/test/patterns.test.js       | 22 ++++++++++++++++++-
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/packages/patterns/src/patterns/patternMatchers.js b/packages/patterns/src/patterns/patternMatchers.js
index 18cc63578a..1580003b28 100644
--- a/packages/patterns/src/patterns/patternMatchers.js
+++ b/packages/patterns/src/patterns/patternMatchers.js
@@ -937,6 +937,7 @@ const makePatternKit = () => {
       let style;
       switch (kind) {
         case 'copySet':
+        case 'copyBag':
         case 'copyMap': {
           style = 'tagged';
           break;
diff --git a/packages/patterns/test/patterns.test.js b/packages/patterns/test/patterns.test.js
index e8f9faca50..c7196e7657 100644
--- a/packages/patterns/test/patterns.test.js
+++ b/packages/patterns/test/patterns.test.js
@@ -12,7 +12,12 @@ import {
   isKey,
   assertKey,
 } from '../src/keys/checkKey.js';
-import { mustMatch, matches, M } from '../src/patterns/patternMatchers.js';
+import {
+  mustMatch,
+  matches,
+  M,
+  getRankCover,
+} from '../src/patterns/patternMatchers.js';
 
 const { stringify: q } = JSON;
 
@@ -971,3 +976,18 @@ test('Far functions (callable remotables) are valid Keys', t => {
   const set = makeCopySet([farFn]);
   t.true(matches(set, M.set()));
 });
+
+test('getRankCover treats copyBag like other tagged kinds (#3052)', t => {
+  // copySet, copyBag, and copyMap all encode as the 'tagged' pass style,
+  // so getRankCover must produce the same range for each. Previously
+  // copyBag fell through to the default branch and threw a TypeError
+  // because 'copyBag' is not a known PassStyle.
+  // The kind matcher's getRankCover does not consult encodePassable, so
+  // this test does not require a real encoder.
+  const stubEncode = () => '';
+  const setCover = getRankCover(M.kind('copySet'), stubEncode);
+  const bagCover = getRankCover(M.kind('copyBag'), stubEncode);
+  const mapCover = getRankCover(M.kind('copyMap'), stubEncode);
+  t.deepEqual(bagCover, setCover);
+  t.deepEqual(bagCover, mapCover);
+});