From f11ad9028e88cae49788a461c7b1feccec9e57be Mon Sep 17 00:00:00 2001
From: Sam Vervaeck <samvv@pm.me>
Date: Thu, 15 Sep 2022 23:05:34 +0200
Subject: [PATCH] Fix wrong node being printed when diagnosing the origin of a
 type

---
 src/checker.ts | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/checker.ts b/src/checker.ts
index 4e3f3303d..e99a745df 100644
--- a/src/checker.ts
+++ b/src/checker.ts
@@ -1356,7 +1356,12 @@ export class Checker {
             return this.createTypeVar();
           }
           type = this.instantiate(scheme, node.name);
-          // FIXME it is not guaranteed that `type` is copied, so the original type might get mutated
+          // It is not guaranteed that `type` is copied during instantiation,
+          // so the following check ensures that we really are holding a copy
+          // that we can mutate.
+          if (type === scheme.type) {
+            type = type.shallowClone();
+          }
           type.node = node;
           break;
         }