From 517f32940ad44933f8bb3b5d07e8c830cbfc40ea Mon Sep 17 00:00:00 2001
From: Wesley Wigham <wewigham@microsoft.com>
Date: Wed, 27 Jan 2021 15:30:59 -0800
Subject: [PATCH] Add regression test for #37314 (#42525)

---
 .../conditionalEqualityTestingNullability.js  | 19 ++++++++
 ...ditionalEqualityTestingNullability.symbols | 43 +++++++++++++++++++
 ...onditionalEqualityTestingNullability.types | 26 +++++++++++
 .../conditionalEqualityTestingNullability.ts  | 15 +++++++
 4 files changed, 103 insertions(+)
 create mode 100644 tests/baselines/reference/conditionalEqualityTestingNullability.js
 create mode 100644 tests/baselines/reference/conditionalEqualityTestingNullability.symbols
 create mode 100644 tests/baselines/reference/conditionalEqualityTestingNullability.types
 create mode 100644 tests/cases/compiler/conditionalEqualityTestingNullability.ts

diff --git a/tests/baselines/reference/conditionalEqualityTestingNullability.js b/tests/baselines/reference/conditionalEqualityTestingNullability.js
new file mode 100644
index 0000000000..3c30da8a0f
--- /dev/null
+++ b/tests/baselines/reference/conditionalEqualityTestingNullability.js
@@ -0,0 +1,19 @@
+//// [conditionalEqualityTestingNullability.ts]
+export type Equals<A1 extends any, A2 extends any> =
+    (<A>() => A extends A1 ? 1 : 0) extends (<A>() => A extends A2 ? 1 : 0)
+    ? 1
+    : 0
+
+interface Foo<T> {
+    x : () => T
+}
+
+declare const a: Foo<Date>;
+declare const b: Foo<Date | null>;
+
+//Expected 0, Actual 1
+type ShouldBe0 = Equals<typeof a, typeof b>;
+
+//// [conditionalEqualityTestingNullability.js]
+"use strict";
+exports.__esModule = true;
diff --git a/tests/baselines/reference/conditionalEqualityTestingNullability.symbols b/tests/baselines/reference/conditionalEqualityTestingNullability.symbols
new file mode 100644
index 0000000000..c1ede984fb
--- /dev/null
+++ b/tests/baselines/reference/conditionalEqualityTestingNullability.symbols
@@ -0,0 +1,43 @@
+=== tests/cases/compiler/conditionalEqualityTestingNullability.ts ===
+export type Equals<A1 extends any, A2 extends any> =
+>Equals : Symbol(Equals, Decl(conditionalEqualityTestingNullability.ts, 0, 0))
+>A1 : Symbol(A1, Decl(conditionalEqualityTestingNullability.ts, 0, 19))
+>A2 : Symbol(A2, Decl(conditionalEqualityTestingNullability.ts, 0, 34))
+
+    (<A>() => A extends A1 ? 1 : 0) extends (<A>() => A extends A2 ? 1 : 0)
+>A : Symbol(A, Decl(conditionalEqualityTestingNullability.ts, 1, 6))
+>A : Symbol(A, Decl(conditionalEqualityTestingNullability.ts, 1, 6))
+>A1 : Symbol(A1, Decl(conditionalEqualityTestingNullability.ts, 0, 19))
+>A : Symbol(A, Decl(conditionalEqualityTestingNullability.ts, 1, 46))
+>A : Symbol(A, Decl(conditionalEqualityTestingNullability.ts, 1, 46))
+>A2 : Symbol(A2, Decl(conditionalEqualityTestingNullability.ts, 0, 34))
+
+    ? 1
+    : 0
+
+interface Foo<T> {
+>Foo : Symbol(Foo, Decl(conditionalEqualityTestingNullability.ts, 3, 7))
+>T : Symbol(T, Decl(conditionalEqualityTestingNullability.ts, 5, 14))
+
+    x : () => T
+>x : Symbol(Foo.x, Decl(conditionalEqualityTestingNullability.ts, 5, 18))
+>T : Symbol(T, Decl(conditionalEqualityTestingNullability.ts, 5, 14))
+}
+
+declare const a: Foo<Date>;
+>a : Symbol(a, Decl(conditionalEqualityTestingNullability.ts, 9, 13))
+>Foo : Symbol(Foo, Decl(conditionalEqualityTestingNullability.ts, 3, 7))
+>Date : Symbol(Date, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --), Decl(lib.scripthost.d.ts, --, --))
+
+declare const b: Foo<Date | null>;
+>b : Symbol(b, Decl(conditionalEqualityTestingNullability.ts, 10, 13))
+>Foo : Symbol(Foo, Decl(conditionalEqualityTestingNullability.ts, 3, 7))
+>Date : Symbol(Date, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --), Decl(lib.scripthost.d.ts, --, --))
+
+//Expected 0, Actual 1
+type ShouldBe0 = Equals<typeof a, typeof b>;
+>ShouldBe0 : Symbol(ShouldBe0, Decl(conditionalEqualityTestingNullability.ts, 10, 34))
+>Equals : Symbol(Equals, Decl(conditionalEqualityTestingNullability.ts, 0, 0))
+>a : Symbol(a, Decl(conditionalEqualityTestingNullability.ts, 9, 13))
+>b : Symbol(b, Decl(conditionalEqualityTestingNullability.ts, 10, 13))
+
diff --git a/tests/baselines/reference/conditionalEqualityTestingNullability.types b/tests/baselines/reference/conditionalEqualityTestingNullability.types
new file mode 100644
index 0000000000..c99571b8fc
--- /dev/null
+++ b/tests/baselines/reference/conditionalEqualityTestingNullability.types
@@ -0,0 +1,26 @@
+=== tests/cases/compiler/conditionalEqualityTestingNullability.ts ===
+export type Equals<A1 extends any, A2 extends any> =
+>Equals : Equals<A1, A2>
+
+    (<A>() => A extends A1 ? 1 : 0) extends (<A>() => A extends A2 ? 1 : 0)
+    ? 1
+    : 0
+
+interface Foo<T> {
+    x : () => T
+>x : () => T
+}
+
+declare const a: Foo<Date>;
+>a : Foo<Date>
+
+declare const b: Foo<Date | null>;
+>b : Foo<Date | null>
+>null : null
+
+//Expected 0, Actual 1
+type ShouldBe0 = Equals<typeof a, typeof b>;
+>ShouldBe0 : 0
+>a : Foo<Date>
+>b : Foo<Date | null>
+
diff --git a/tests/cases/compiler/conditionalEqualityTestingNullability.ts b/tests/cases/compiler/conditionalEqualityTestingNullability.ts
new file mode 100644
index 0000000000..bf06284b72
--- /dev/null
+++ b/tests/cases/compiler/conditionalEqualityTestingNullability.ts
@@ -0,0 +1,15 @@
+// @strict: true
+export type Equals<A1 extends any, A2 extends any> =
+    (<A>() => A extends A1 ? 1 : 0) extends (<A>() => A extends A2 ? 1 : 0)
+    ? 1
+    : 0
+
+interface Foo<T> {
+    x : () => T
+}
+
+declare const a: Foo<Date>;
+declare const b: Foo<Date | null>;
+
+//Expected 0, Actual 1
+type ShouldBe0 = Equals<typeof a, typeof b>;
\ No newline at end of file