tsgo reports downstream TS2339 in ignored for-of over non-iterable union that tsc 6.0.2 does not

[songkeys]

TypeScript Version

• tsc 6.0.2
• tsgo 7.0.0-dev.20260421.2

Search Terms

for...of, @ts-ignore, TS2488, TS2339, error recovery, parity

Code

type A = {
  a: string
}

type B = {
  b: string
}

declare const data: A[] | B

// @ts-ignore
for (const item of data) {
  item.b
}

Commands

tsc --ignoreConfig --noEmit --strict --target es2022 case4.ts
tsc --ignoreConfig --noEmit --strict --target es2022 --stableTypeOrdering case4.ts
tsgo --ignoreConfig --noEmit --strict --target es2022 case4.ts

Expected Behavior

tsgo should match tsc 6.0.2 here.

With the @ts-ignore on the for...of line, tsc 6.0.2 reports no errors, including with --stableTypeOrdering.

Actual Behavior

tsgo reports:

case4.ts(13,8): error TS2339: Property 'b' does not exist on type 'A'.

Additional Notes

If I remove the @ts-ignore, tsc 6.0.2 reports only the for...of error (TS2488), while tsgo reports both the TS2488 and the downstream TS2339 in the loop body.

So this appears to be a parity difference in error recovery or loop variable typing after an invalid for...of.