From 739ab63567065fc18fb486930a6f5166386e4e94 Mon Sep 17 00:00:00 2001
From: Andrii Furmanets <furmanets.andriy@gmail.com>
Date: Wed, 29 Apr 2026 21:53:28 +0300
Subject: [PATCH] Fix Intl.Collator compare declaration

---
 src/lib/es5.d.ts                              |  2 +-
 .../intlCollatorCompareAccessor.errors.txt    | 25 +++++++++++++++++++
 .../compiler/intlCollatorCompareAccessor.ts   | 15 +++++++++++
 3 files changed, 41 insertions(+), 1 deletion(-)
 create mode 100644 tests/baselines/reference/intlCollatorCompareAccessor.errors.txt
 create mode 100644 tests/cases/compiler/intlCollatorCompareAccessor.ts

diff --git a/src/lib/es5.d.ts b/src/lib/es5.d.ts
index ced21a6d72af1..eedba9e8809fa 100644
--- a/src/lib/es5.d.ts
+++ b/src/lib/es5.d.ts
@@ -4419,7 +4419,7 @@ declare namespace Intl {
     }
 
     interface Collator {
-        compare(x: string, y: string): number;
+        readonly compare: (this: void, x: string, y: string) => number;
         resolvedOptions(): ResolvedCollatorOptions;
     }
 
diff --git a/tests/baselines/reference/intlCollatorCompareAccessor.errors.txt b/tests/baselines/reference/intlCollatorCompareAccessor.errors.txt
new file mode 100644
index 0000000000000..8f48d7cea48c3
--- /dev/null
+++ b/tests/baselines/reference/intlCollatorCompareAccessor.errors.txt
@@ -0,0 +1,25 @@
+intlCollatorCompareAccessor.ts(7,7): error TS2322: Type '(this: Intl.Collator, x: string, y: string) => number' is not assignable to type '(this: void, x: string, y: string) => number'.
+  The 'this' types of each signature are incompatible.
+    Type 'void' is not assignable to type 'Collator'.
+intlCollatorCompareAccessor.ts(11,10): error TS2540: Cannot assign to 'compare' because it is a read-only property.
+
+
+==== intlCollatorCompareAccessor.ts (2 errors) ====
+    declare const collator: Intl.Collator;
+    
+    collator.compare("a", "b");
+    ["a", "b"].sort(collator.compare);
+    
+    const compare: (this: void, x: string, y: string) => number = collator.compare;
+    const compareWithThis: Intl.Collator["compare"] = function (this: Intl.Collator, x: string, y: string) {
+          ~~~~~~~~~~~~~~~
+!!! error TS2322: Type '(this: Intl.Collator, x: string, y: string) => number' is not assignable to type '(this: void, x: string, y: string) => number'.
+!!! error TS2322:   The 'this' types of each signature are incompatible.
+!!! error TS2322:     Type 'void' is not assignable to type 'Collator'.
+        return 0;
+    };
+    
+    collator.compare = (x: string, y: string) => 0;
+             ~~~~~~~
+!!! error TS2540: Cannot assign to 'compare' because it is a read-only property.
+    
\ No newline at end of file
diff --git a/tests/cases/compiler/intlCollatorCompareAccessor.ts b/tests/cases/compiler/intlCollatorCompareAccessor.ts
new file mode 100644
index 0000000000000..423876cb7bb1d
--- /dev/null
+++ b/tests/cases/compiler/intlCollatorCompareAccessor.ts
@@ -0,0 +1,15 @@
+// @strict: true
+// @noEmit: true
+// @noTypesAndSymbols: true
+
+declare const collator: Intl.Collator;
+
+collator.compare("a", "b");
+["a", "b"].sort(collator.compare);
+
+const compare: (this: void, x: string, y: string) => number = collator.compare;
+const compareWithThis: Intl.Collator["compare"] = function (this: Intl.Collator, x: string, y: string) {
+    return 0;
+};
+
+collator.compare = (x: string, y: string) => 0;