💅 useExhaustiveSwitchCases misses a union derived from an as const array when imported from another workspace package

[alokn]

Environment information

Details

CLI:
  Version:                      2.5.14
Platform:
  CPU Architecture:             aarch64
  OS:                           macos
Environment:
  JS_RUNTIME_NAME:              node
  NODE_PACKAGE_MANAGER:         pnpm/11.24.0
Biome Configuration:
  Status:                       Loaded successfully.
  Path:                         biome.json
  Linter enabled:               true

Rule name

nursery/useExhaustiveSwitchCases

Playground link

Not reproducible in the playground (needs two workspace packages). Full repro below.

What happened?

useExhaustiveSwitchCases does not report a non-exhaustive switch when the discriminant's type is a union derived as (typeof ARR)[number] and imported from another workspace package. The same switch over a locally declared copy of the union is reported. #6929 and #11730 report similar gaps and are closed; this is the workspace-package import case, which still reproduces on 2.5.14.

Repro (pnpm workspace):

package.json                     { "devDependencies": { "@biomejs/biome": "2.5.14" } }
pnpm-workspace.yaml              packages: ["packages/*"]
biome.json                       { "linter": { "enabled": true, "rules": { "nursery": { "useExhaustiveSwitchCases": "error" } } } }
packages/lib/package.json        { "name": "@repro/lib", "version": "1.0.0", "main": "src/index.ts", "types": "src/index.ts" }
packages/app/package.json        { "name": "@repro/app", "version": "1.0.0", "dependencies": { "@repro/lib": "workspace:*" } }

packages/lib/src/index.ts:

export const S = ["a", "b", "c"] as const;
export type S = (typeof S)[number];

packages/app/src/cross.ts (imported union, case "c" missing, no default):

import type { S } from "@repro/lib";

export function f(x: S): number {
  switch (x) {
    case "a":
      return 1;
    case "b":
      return 2;
  }
  return 0;
}

packages/app/src/local.ts (same union declared locally, same missing case):

const L = ["a", "b", "c"] as const;
type L = (typeof L)[number];

export function g(x: L): number {
  switch (x) {
    case "a":
      return 1;
    case "b":
      return 2;
  }
  return 0;
}

Steps: pnpm install, then pnpm exec biome lint packages.

Result: only local.ts is reported (The switch statement is not exhaustive ... These cases are missing: - "c"). pnpm exec biome lint packages/app/src/cross.ts prints Checked 1 file in 2ms. No fixes applied. with no diagnostic.

Expected result

cross.ts is reported with the missing case "c", as local.ts is.

Code of Conduct

• I agree to follow Biome's Code of Conduct

[biome-cookie]

Hello @alokn, please provide a minimal reproduction. You can use one of the following options:

• Provide a link to our playground, if it's applicable.
• Provide a link to GitHub repository. To easily create a reproduction, you can use our interactive CLI via npm create @biomejs/biome-reproduction

Issues marked with S-Needs repro will be closed if they have no activity within 3 days.

[alokn]

Reproduction repository: https://github.com/alokn/biome-exhaustive-switch-cross-package

It uses the create-biome-reproduction template layout, extended to a pnpm workspace, because the playground can't show an import across workspace packages. Run pnpm install && pnpm lint on Biome 2.5.14: packages/app/src/local.ts is reported (missing "c"), but the same switch in packages/app/src/cross.ts, over the union imported from @repro/lib, is not.

[dyc3]

I can reproduce this on current main.

The bug occurs because there is a value and a type that share the same name, eg const L and type L. Some sort of shadowing is happening, and I don't think we properly check if the binding is in a type annotation position or a value position before resolving it. Its a bit tricky