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feat: add const type parameter to isLiteralOneOf #137

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Merged
merged 1 commit into from
Nov 28, 2025
+19 −2
Merged

feat: add const type parameter to isLiteralOneOf #137

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5 changes: 5 additions & 0 deletions deno.jsonc
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,11 @@
"compilerOptions": {
"exactOptionalPropertyTypes": true
},
"lint": {
"rules": {
"exclude": ["no-import-prefix"]
}
},
Comment on lines +9 to +11
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Copilot AI Nov 28, 2025

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This lint configuration change appears unrelated to the PR's main purpose of adding a const type parameter to isLiteralOneOf. The entire codebase already uses relative imports (e.g., "../_funcutil.ts", "./literal_one_of.ts"), so if no-import-prefix was actually causing issues, it would affect many files.

Consider removing this unrelated change from the PR, or if it's needed, explain why in the PR description and potentially submit it as a separate change.

Suggested change
"exclude": ["no-import-prefix"]
}
},
}
},
},

Copilot uses AI. Check for mistakes.
"exports": {
".": "./mod.ts",
"./as": "./as/mod.ts",
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4 changes: 2 additions & 2 deletions is/literal_one_of.ts
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Expand Up @@ -12,14 +12,14 @@ import type { Predicate, Primitive } from "../type.ts";
* ```ts
* import { is } from "@core/unknownutil";
*
* const isMyType = is.LiteralOneOf(["hello", "world"] as const);
* const isMyType = is.LiteralOneOf(["hello", "world"]);
* const a: unknown = "hello";
* if (isMyType(a)) {
* const _: "hello" | "world" = a;
* }
* ```
*/
export function isLiteralOneOf<T extends readonly Primitive[]>(
export function isLiteralOneOf<const T extends readonly Primitive[]>(
literals: T,
): Predicate<T[number]> {
const s = new Set(literals);
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12 changes: 12 additions & 0 deletions is/literal_one_of_test.ts
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Expand Up @@ -28,4 +28,16 @@ Deno.test("isLiteralOneOf<T>", async (t) => {
assertType<IsExact<typeof a, "hello" | "world">>(true);
}
});

await t.step("works without as const assertion", () => {
const predicate = isLiteralOneOf(["foo", "bar"]);
assertEquals(predicate("foo"), true);
assertEquals(predicate("bar"), true);
assertEquals(predicate("baz"), false);

const b: unknown = "foo";
if (predicate(b)) {
assertType<IsExact<typeof b, "foo" | "bar">>(true);
}
});
});