Internal crash with `TypeError: Cannot read properties of undefined (reading 'parent')`

[geritol]

🔎 Search Terms

Project works fine with typescript version 4.8.4, when upgrading to 4.9.4 (and any further version) type checking crashes with an internal error.

🕗 Version & Regression Information

• This is a crash
• This changed between versions 4.8.4 and 4.9.4
• Error is present with typescript@next (Version 5.5.0-dev.20240229)

With the help of every-ts bisect I found the first bad commit to be:

42f9143e114c5c07f40df83ed07ffeb3cbaf2101 is the first bad commit
commit 42f9143e114c5c07f40df83ed07ffeb3cbaf2101
Author: Jack Works <jackworks@protonmail.com>
Date:   Fri Sep 30 07:13:25 2022 +0800

    feat: codefix for `for await of` (#50623)

 src/compiler/checker.ts                                | 18 +++++++++++++++++-
 src/compiler/types.ts                                  |  1 +
 src/services/codefixes/addMissingAwait.ts              |  9 +++++++++
 .../fourslash/codeFixAddMissingAwait_forAwaitOf.ts     | 17 +++++++++++++++++
 4 files changed, 44 insertions(+), 1 deletion(-)
 create mode 100644 tests/cases/fourslash/codeFixAddMissingAwait_forAwaitOf.ts

https://github.com/microsoft/TypeScript/pull/50623/files

I think error might come from errorNode being undefined here:

⏯ Playground Link

No response

💻 Code

No response

🙁 Actual behavior

> tsc --noEmit

[...]/node_modules/typescript/lib/tsc.js:99607
                throw e;
                ^

TypeError: Cannot read properties of undefined (reading 'parent')
    at reportTypeNotIterableError ([...]/node_modules/typescript/lib/tsc.js:71494:51)
    at getIteratedTypeOrElementType ([...]/node_modules/typescript/lib/tsc.js:71168:17)
    at checkIteratedTypeOrElementType ([...]/node_modules/typescript/lib/tsc.js:71163:20)
    at getTypeOfDestructuredArrayElement [...]/node_modules/typescript/lib/tsc.js:59574:50)
    at getAssignedTypeOfArrayLiteralElement ([...]/node_modules/typescript/lib/tsc.js:59599:20)
    at getAssignedType ([...]/node_modules/typescript/lib/tsc.js:59622:28)
    at getInitialOrAssignedType ([...]/node_modules/typescript/lib/tsc.js:60250:21)
    at getTypeAtFlowAssignment ([...]/node_modules/typescript/lib/tsc.js:60266:66)
    at getTypeAtFlowNode ([...]/node_modules/typescript/lib/tsc.js:60181:32)
    at getTypeAtFlowBranchLabel ([...]/node_modules/typescript/lib/tsc.js:60405:36)

Node.js v20.9.0

🙂 Expected behavior

no internal crash when upgrading versions

Additional information about the issue

No response

[Andarist]

It might be quite hard to investigate this without a repro case. Would you be able to reduce your repository to one?

[geritol]

Don't think so, it is a huge private repository

[jakebailey]

Wild guess, but I bet it has to do with:

    /**
     * When consuming an iterable type in a for..of, spread, or iterator destructuring assignment
     * we want to get the iterated type of an iterable for ES2015 or later, or the iterated type
     * of a iterable (if defined globally) or element type of an array like for ES2015 or earlier.
     */
    function getIteratedTypeOrElementType(use: IterationUse, inputType: Type, sentType: Type, errorNode: Node | undefined, checkAssignability: boolean): Type | undefined {
        const allowAsyncIterables = (use & IterationUse.AllowsAsyncIterablesFlag) !== 0;
        if (inputType === neverType) {
            reportTypeNotIterableError(errorNode!, inputType, allowAsyncIterables); // TODO: GH#18217
            return undefined;
        }

Note errorNode!; possibly a case where one needs to iterate over never?

[geritol]

I have found what was causing the issue for us (valid js file with buggy implementation let someVar; [someVar] = someValue), but could not isolate a reproduction yet, will try further

[jakebailey]

Yeah, this is an error path, so it's crashing instead of telling you about said bug, I would assume.

[geritol]

I think it is valid js (destructuring), and we had no issues reported in previous typescript versions. But if I remove the destructuring (or set the file to @ts-nocheck) crash is solved.

[jakebailey]

It's valid JS, it's just code which fails to typecheck and would error but instead crashes.

[geritol]

managed to create a reproduction!
https://github.com/geritol/ts-bug-repro-57582