Bug Report

🔎 Search Terms

default import, default export, named default export, module resolution, node 16

🕗 Version & Regression Information

Version 4.7.3

I also tried nightly, it is present there too.

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about default imports/exports
• I was unable to test this on prior versions because they didn't have the node16 setting

⏯ Playground Link

Can't use playground because it requires multiple files.

https://github.com/calebeby/ts-import-bug

💻 Code

In node, mod2 and def are the "CJS namespace import" as described in the Node docs.

import mod2, {default as def} from 'foo'

// TS thinks this is false; it is actually true
console.log(def === mod2)

// TS thinks this works but it doesn't (at runtime def === mod2)
def()

foo.d.ts:

export declare function def(): void
export default def

If I switch moduleResolution to node, mod2 and def have the same type (not matching node's native ESM behavior, but that is expected since moduleResolution is not set to node16)

🙁 Actual behavior

a.mts:11:13 - error TS2367: This condition will always return 'false' since the types '() => void' and 'typeof import("/Users/calebeby/Projects/ts-import-bug/foo/foo")' have no overlap.

🙂 Expected behavior

def and mod2 should have the same type (the CJS namespace). TS should say that the def() line is an error. def === mod2 should not say This condition will always return 'false'