From 1a2df0ee4b5bf613309e5f367daab8c9238d9a2e Mon Sep 17 00:00:00 2001
From: Phil Pluckthun <phil@kitten.sh>
Date: Sun, 18 Aug 2024 18:39:12 +0100
Subject: [PATCH] fix: Improve type output for narrowed interfaces (intersect
 members of unions instead) (#370)

---
 .changeset/wild-tables-serve.md | 5 +++++
 src/selection.ts                | 8 ++++++--
 2 files changed, 11 insertions(+), 2 deletions(-)
 create mode 100644 .changeset/wild-tables-serve.md

diff --git a/.changeset/wild-tables-serve.md b/.changeset/wild-tables-serve.md
new file mode 100644
index 00000000..bcbd0a5f
--- /dev/null
+++ b/.changeset/wild-tables-serve.md
@@ -0,0 +1,5 @@
+---
+"gql.tada": patch
+---
+
+Improve type output readability for interfaces with narrowed types
diff --git a/src/selection.ts b/src/selection.ts
index 06c61694..bb6ba9b5 100644
--- a/src/selection.ts
+++ b/src/selection.ts
@@ -12,6 +12,8 @@ type ObjectLikeType = {
   fields: { [key: string]: any };
 };
 
+type narrowTypename<T, Typename> = T extends { __typename?: Typename } ? T : never;
+
 type unwrapTypeRec<
   Type,
   SelectionSet,
@@ -95,7 +97,7 @@ type getFragmentSelection<
       ? Fragments[Node['name']['value']] extends { [$tada.ref]: any }
         ? Type extends { kind: 'INTERFACE'; name: any }
           ? /* This protects against various edge cases where users forget to select `__typename` (See `getSelection`) */
-            Fragments[Node['name']['value']][$tada.ref] & { __typename?: PossibleType }
+            narrowTypename<Fragments[Node['name']['value']][$tada.ref], PossibleType>
           : Fragments[Node['name']['value']][$tada.ref]
         : getPossibleTypeSelectionRec<
             Fragments[Node['name']['value']]['selectionSet']['selections'],
@@ -227,7 +229,9 @@ type getPossibleTypeSelectionRec<
               >
           : SelectionAcc
     >
-  : obj<SelectionAcc['fields']> & SelectionAcc['rest'];
+  : SelectionAcc['rest'] extends infer T
+    ? obj<SelectionAcc['fields'] & T>
+    : never;
 
 type getOperationSelectionType<
   Definition,