From d2b0c2b7bd2acc181b6f2b4e15420333be7033fb Mon Sep 17 00:00:00 2001
From: Rebecca Stevens <rebecca.stevens@outlook.co.nz>
Date: Mon, 14 Feb 2022 22:53:58 +1300
Subject: [PATCH] fix(DeepEqualAssertion): allow Actual and Expected types not
 to extend each other

fix #2964
---
 test-d/deep-equal.ts  | 32 ++++++++++++++++++++++++++++++++
 types/assertions.d.ts | 12 ++++++++++++
 2 files changed, 44 insertions(+)
 create mode 100644 test-d/deep-equal.ts

diff --git a/test-d/deep-equal.ts b/test-d/deep-equal.ts
new file mode 100644
index 0000000000..a7c5984419
--- /dev/null
+++ b/test-d/deep-equal.ts
@@ -0,0 +1,32 @@
+import {expectType} from 'tsd';
+
+import test from '..';
+
+test('actual extends expected', t => {
+	type Expected = {foo: [1, 2, 3]};
+	const expected: Expected = {foo: [1, 2, 3]};
+	const actual = {foo: [1, 2, 3]};
+	if (t.deepEqual(actual, expected)) {
+		expectType<Expected>(actual);
+	}
+});
+
+test('expected extends actual', t => {
+	type Expected = {foo: Array<number | string>};
+	type Actual = {foo: number[]};
+	const expected: Expected = {foo: [1, 2, 3]};
+	const actual: Actual = {foo: [1, 2, 3]};
+	if (t.deepEqual(actual, expected)) {
+		expectType<Actual>(expected);
+	}
+});
+
+test('neither exectend each other', t => {
+	type Expected = {readonly foo: readonly [1, 2, 3]};
+	type Actual = {foo: number[]};
+	const expected: Expected = {foo: [1, 2, 3]};
+	const actual: Actual = {foo: [1, 2, 3]};
+	if (t.deepEqual(actual, expected)) {
+		t.pass();
+	}
+});
diff --git a/types/assertions.d.ts b/types/assertions.d.ts
index 657ed3d486..ce5a97a140 100644
--- a/types/assertions.d.ts
+++ b/types/assertions.d.ts
@@ -138,6 +138,18 @@ export interface DeepEqualAssertion {
 	 */
 	<Actual, Expected extends Actual>(actual: Actual, expected: Expected, message?: string): actual is Expected;
 
+	/**
+	 * Assert that `actual` is [deeply equal](https://github.com/concordancejs/concordance#comparison-details) to
+	 * `expected`, returning a boolean indicating whether the assertion passed.
+	 */
+	<Actual extends Expected, Expected>(actual: Actual, expected: Expected, message?: string): expected is Actual;
+
+	/**
+	 * Assert that `actual` is [deeply equal](https://github.com/concordancejs/concordance#comparison-details) to
+	 * `expected`, returning a boolean indicating whether the assertion passed.
+	 */
+	<Actual, Expected>(actual: Actual, expected: Expected, message?: string): boolean;
+
 	/** Skip this assertion. */
 	skip(actual: any, expected: any, message?: string): void;
 }