ConditionalPick: Fix returning {} instead of never when no keys match (#1359)

Co-authored-by: Som Shekhar Mukherjee <iamssmkhrj@gmail.com>

Author: derodero24

source/conditional-pick.d.ts

@@ -1,4 +1,5 @@
 import type {ConditionalKeys} from './conditional-keys.d.ts';
+import type {IsNever} from './is-never.d.ts';
 
 /**
 Pick keys from the shape that matches the given `Condition`.
@@ -38,9 +39,10 @@ type StringKeysOnly = ConditionalPick<Example, string>;
 
 @category Object
 */
-export type ConditionalPick<Base, Condition> = Pick<
-	Base,
-	ConditionalKeys<Base, Condition>
->;
+export type ConditionalPick<Base, Condition> = ConditionalKeys<Base, Condition> extends infer Keys
+	? IsNever<Keys> extends true
+		? never
+		: Pick<Base, Keys & keyof Base>
+	: never;
 
 export {};

test-d/conditional-pick.ts

@@ -26,3 +26,10 @@ expectType<{name: string; successes: number; failures: bigint}>(awesomeCondition
 
 declare const exampleConditionalPickWithUndefined: ConditionalPick<Example, string | undefined>;
 expectType<{a: string; c?: string}>(exampleConditionalPickWithUndefined);
+
+// Returns `never` when no keys match the condition
+declare const noMatchingKeys: ConditionalPick<Example, number>;
+expectType<never>(noMatchingKeys);
+
+declare const noMatchingKeys2: ConditionalPick<{a: string; b: number}, boolean>;
+expectType<never>(noMatchingKeys2);