fix contravariance of writeable state:

DefinitelyTyped · May 29, 2020 · f6ddc8d · f6ddc8d
1 parent 4128d12
commit f6ddc8d
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Showing 2 changed files with 22 additions and 4 deletions.
diff --git a/types/recoil/index.d.ts b/types/recoil/index.d.ts
@@ -158,15 +158,16 @@ export type Loadable<T> =
 
 // recoilValue.d.ts
 export class AbstractRecoilValue<T> {
-    tag: 'Writeable';
-    valTag: T;
+    __tag: [T];
+    __cTag: (t: T) => void; // for contravariance
+
     key: NodeKey;
     constructor(newKey: NodeKey);
 }
 
 export class AbstractRecoilValueReadonly<T> {
-    tag: 'Readonly';
-    valTag: T;
+    __tag: [T];
+
     key: NodeKey;
     constructor(newKey: NodeKey);
 }

diff --git a/types/recoil/recoil-tests.ts b/types/recoil/recoil-tests.ts
@@ -12,6 +12,7 @@ import {
     useResetRecoilState,
     useRecoilCallback,
     isRecoilValue,
+    RecoilState,
 } from 'recoil';
 // import { atomFamily } from 'recoil/utils';
 
@@ -73,6 +74,22 @@ RecoilRoot({
 });
 
 // Hooks
+const roAtom: RecoilValueReadOnly<string> = {} as any;
+const waAtom: RecoilState<string> = {} as any;
+const nsAtom: RecoilState<number | string> = {} as any; // number or string
+
+useRecoilValue(roAtom);
+useRecoilValue(waAtom);
+
+useRecoilState(roAtom); // $ExpectError
+useRecoilState(waAtom);
+
+useRecoilState<number>(waAtom); // $ExpectError
+useRecoilState<number | string>(waAtom); // $ExpectError
+useRecoilValue<number>(waAtom); // $ExpectError
+useRecoilValue<number | string>(waAtom);
+useRecoilValue<number>(nsAtom); // $ExpectError
+
 useRecoilValue(myAtom);
 useRecoilValue(mySelector1);
 useRecoilValue(readOnlySelector);