From 027fe217c1547c8080f1a15a775ce6d8065ef2ab Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Thu, 17 Dec 2020 06:52:42 -1000
Subject: [PATCH] Add regression tests

---
 .../cases/compiler/strictSubtypeReduction.ts  | 34 +++++++++++++++++++
 1 file changed, 34 insertions(+)
 create mode 100644 tests/cases/compiler/strictSubtypeReduction.ts

diff --git a/tests/cases/compiler/strictSubtypeReduction.ts b/tests/cases/compiler/strictSubtypeReduction.ts
new file mode 100644
index 00000000000..9323e3deca7
--- /dev/null
+++ b/tests/cases/compiler/strictSubtypeReduction.ts
@@ -0,0 +1,34 @@
+// @strict: true
+
+// Repro from #41977
+
+class S1 {
+  static f(a: number | string): void {}
+}
+
+class S2 {
+  static f(a: number): void {}
+  static g(a: number): void {}
+}
+
+function f(a: number): void {}
+function g(a: number): void {}
+
+// Declaring the following type aliases should have no effect
+
+type T1 = typeof S2.g;
+type T2 = typeof g;
+
+// All should have type ((a: number) => void)[]
+
+const y1 = [S1.f, f];
+const y2 = [S1.f, g];
+const y3 = [S1.f, S2.f];
+const y4 = [S1.f, S2.g];
+
+// All assignments should be errors
+
+const x1: ((ctrl: number | string) => void)[] = y1;
+const x2: ((ctrl: number | string) => void)[] = y2;
+const x3: ((ctrl: number | string) => void)[] = y3;
+const x4: ((ctrl: number | string) => void)[] = y4;