From 3c796467b8c05bca6363585b4eb4f15c5404e9c8 Mon Sep 17 00:00:00 2001
From: gvergnaud <gabriel.vergnaud@gmail.com>
Date: Wed, 19 Jul 2023 11:13:39 -0400
Subject: [PATCH] =?UTF-8?q?=F0=9F=90=9B=20fix:=20Accept=20branded=20primit?=
 =?UTF-8?q?ive=20types=20as=20patterns?=
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TS-Pattern v4 used to support branded types, usually defined as an intersection
between a literal type (like `number` or `string`) and an object containing a unique symbol.
There is a bug in v5 that prevents people from using branded types as patterns and this PR fixes it.

This closes issue #167 and #178.
---
 src/types/Pattern.ts                |  2 +-
 tests/branded-nominal-types.test.ts | 34 +++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/src/types/Pattern.ts b/src/types/Pattern.ts
index e66ce02a..1ae6bc5e 100644
--- a/src/types/Pattern.ts
+++ b/src/types/Pattern.ts
@@ -158,7 +158,7 @@ type KnownPatternInternal<
   a,
   objs = Exclude<a, Primitives | Map<any, any> | Set<any> | readonly any[]>,
   arrays = Extract<a, readonly any[]>,
-  primitives = Exclude<a, object>
+  primitives = Extract<a, Primitives>
 > =
   | primitives
   | PatternMatcher<a>
diff --git a/tests/branded-nominal-types.test.ts b/tests/branded-nominal-types.test.ts
index b992b3df..1564d40b 100644
--- a/tests/branded-nominal-types.test.ts
+++ b/tests/branded-nominal-types.test.ts
@@ -23,4 +23,38 @@ describe('Branded strings', () => {
         .otherwise(() => 'nope')
     ).toEqual('Match: value');
   });
+
+  it('issue #167', () => {
+    const tag: unique symbol = Symbol();
+    type Tagged<Token> = { readonly [tag]: Token };
+    type Opaque<Type, Token = unknown> = Type & Tagged<Token>;
+
+    const opaqueString = (Math.random() > 0.5 ? 'A' : 'B') as Opaque<'A' | 'B'>;
+
+    match(opaqueString)
+      .with('A' as Opaque<'A'>, () => 1)
+      .with('B' as Opaque<'B'>, () => 2)
+      .exhaustive();
+  });
+
+  it('issue #178', () => {
+    const symbol: unique symbol = Symbol();
+
+    interface Branded<key extends string> {
+      [symbol]: { [k in key]: true };
+    }
+
+    type Brand<a, key extends string> = a & Branded<key>;
+    type BrandId = Brand<number, 'BrandId'>;
+
+    const a: number = 1;
+    const b: BrandId = 1 as BrandId;
+
+    expect(
+      match({ a, b })
+        .with({ a, b }, () => '1')
+        .with({ a: P.number, b: P.number }, () => '2')
+        .exhaustive()
+    ).toEqual('1');
+  });
 });