checker: Default import not flagged when target has no default export (moduleResolution=bundler)”

[dBianchii]

🔎 Search Terms

• default import has no default export
• missing default export not reported
• default import from named exports only
• should error: module has no default export
• no diagnostic for default import
• checker fails default import
• moduleResolution bundler default import
• bundler resolution default import missing
• TypeScript no error default import
• TS1192 Module has no default export not emitted
• TS1192 not raised with bundler
• TS2307 repro default import (historical term)
• composite project default import diagnostic
• monorepo workspace default import diagnostic

🕗 Version & Regression Information

This is the behavior in every version I tried (TypeScript 5.9.2 and typescript@next as of 2025‑08‑09)

⏯ Playground Link

https://github.com/dBianchii/ts2307-repro

💻 Code

// strict: true
// target: ES2022
// module: ESNext
// moduleResolution: bundler
// verbatimModuleSyntax: true
// allowSyntheticDefaultImports: false
// esModuleInterop: true

// filename: a.ts
export const test = () => "test";

// filename: b.ts
import Test from "./a"; // should error: module './a' has no default export
console.log(Test.test());

🙁 Actual behavior

pnpm -F @ts2307-repro/b typecheck (or just running tsc --build or even just tsc) completes with exit code 0 and no diagnostics, even though @ts2307-repro/b does a default import from a module that only has named exports.

🙂 Expected behavior

TypeScript should emit an error for the default import because ./a (or @ts2307-repro/a/src/Utils) has no default export.
The build should fail (non‑zero exit) under moduleResolution: bundler.

Additional information about the issue

Repros on macOS (Darwin 26.0 pnpm 10.13.1, TypeScript 5.9.2 and typescript@next (as of today).