Merge pull request #175 from gvergnaud/gvergnaud/fix-re-export-of-pat…

…terns

🐛 fix: Allow re-exporting patterns from ES Modules

README.md

@@ -1531,6 +1531,20 @@ const posts = await fetch(someUrl)
 
 Although not strictly necessary, using `as const` after the pattern definition ensures that TS-Pattern infers the most precise types possible.
 
+### `P.narrow`
+
+`P.narrow<Input, typeof Pattern>` will narrow the input type to only keep the set of values that are compatible with the provided pattern type.
+
+```ts
+type Input = ['a' | 'b' | 'c', 'a' | 'b' | 'c'];
+const Pattern = ['a', P.union('a', 'b')] as const;
+
+type Narrowed = P.narrow<Input, typeof Pattern>;
+//     ^? ['a', 'a' | 'b']
+```
+
+Note that most of the time, the `match` and `isMatching` functions perform narrowing for you, and you do not need to narrow types yourself.
+
 ### `P.Pattern`
 
 `P.Pattern<T>` is the type of all possible pattern for a generic type `T`.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "ts-pattern",
-  "version": "5.0.2",
+  "version": "5.0.3",
   "description": " The exhaustive Pattern Matching library for TypeScript.",
   "type": "module",
   "source": "src/index.ts",

src/internals/symbols.ts

@@ -22,6 +22,7 @@ export type unset = typeof unset;
 export const isVariadic = Symbol.for('@ts-pattern/isVariadic');
 export type isVariadic = typeof isVariadic;
 
+// can't be a symbol because this key has to be enumerable.
 export const anonymousSelectKey = '@ts-pattern/anonymous-select-key';
 export type anonymousSelectKey = typeof anonymousSelectKey;