"Type error: Type 'k' cannot be used to index type" with skipLibCheck: false

[elliottsj]

Unsure if this is a zod issue or a t3-env issue.

Check out latest commit bfa7645

pnpm install
pnpm build
pnpm build --filter=@examples/nextjs
# observe build passes

Change examples/nextjs/tsconfig.json: set "skipLibCheck": false.

pnpm build --filter=@examples/nextjs

@examples/nextjs:build: ../../packages/nextjs/dist/index.d.ts:28:371
@examples/nextjs:build: Type error: Type 'k' cannot be used to index type 'addQuestionMarks<{ [k_1 in keyof TServer]: TServer[k_1]["_output"]; }>'.
@examples/nextjs:build:
@examples/nextjs:build:   26 |     runtimeEnv: StrictOptions<ClientPrefix, TServer, TClient>["runtimeEnvStrict"];
@examples/nextjs:build:   27 | }
@examples/nextjs:build: > 28 | declare function createEnv<TServer extends Record<string, ZodType> = NonNullable<unknown>, TClient extends Record<`${ClientPrefix}${string}`, ZodType> = NonNullable<unknown>>({ runtimeEnv, ...opts }: Options<TServer, TClient>): (zod.objectUtil.addQuestionMarks<{ [k_1 in keyof TServer]: TServer[k_1]["_output"]; }> extends infer T_3 extends object ? { [k in keyof T_3]: zod.objectUtil.addQuestionMarks<{ [k_1 in keyof TServer]: TServer[k_1]["_output"]; }>[k]; } : never) & (zod.objectUtil.addQuestionMarks<{ [k_2 in keyof TClient]: TClient[k_2]["_output"]; }> extends infer T_4 extends object ? { [k_1 in keyof T_4]: zod.objectUtil.addQuestionMarks<{ [k_2 in keyof TClient]: TClient[k_2]["_output"]; }>[k_1]; } : never) extends infer T ? { [P in keyof T]: ((zod.objectUtil.addQuestionMarks<{ [k_1 in keyof TServer]: TServer[k_1]["_output"]; }> extends infer T_1 extends object ? { [k in keyof T_1]: zod.objectUtil.addQuestionMarks<{ [k_1 in keyof TServer]: TServer[k_1]["_output"]; }>[k]; } : never) & (zod.objectUtil.addQuestionMarks<{ [k_2 in keyof TClient]: TClient[k_2]["_output"]; }> extends infer T_2 extends object ? { [k_1 in keyof T_2]: zod.objectUtil.addQuestionMarks<{ [k_2 in keyof TClient]: TClient[k_2]["_output"]; }>[k_1]; } : never))[P]; } : never;
@examples/nextjs:build:      |                                                                                                                                                                                                                                                                                                                                                                                   ^
@examples/nextjs:build:   29 |
@examples/nextjs:build:   30 | export { createEnv };
@examples/nextjs:build:   31 |
@examples/nextjs:build:  ELIFECYCLE  Command failed with exit code 1.

[juliusmarminge]

not sure 🤔

PS: why would you want skipLibCheck: false?

[elliottsj]

PS: why would you want skipLibCheck: false?

To guard against library type errors bubbling up into application run time errors.

For example:

// index.ts
import MyType, { fn } from 'some-module';

const value: MyType = 'test';
fn(value);

// node_modules/some-module/index.d.ts

export type MyType = A; // A is not declared
export function fn(value: MyType): void;

With skipLibCheck: false, we get a type error: Type error: Cannot find name 'A'.

With skipLibCheck: true, there's no type error, so calling fn(value); will likely result in a run time error.