REPL crash when specifying let or var

[TheDevYellowy]

Version

v24.4.0

Platform

Microsoft Windows NT 10.0.26100.0 x64

Subsystem

REPL

What steps will reproduce the bug?

Launch powershell and type "node" to open the REPL, then type "let" and any letter after that will initiate the crash

2025-07-11_00-37-27.mp4

How often does it reproduce? Is there a required condition?

Every time

What is the expected behavior? Why is that the expected behavior?

The repl doesn't crash and allows variable declaration

What do you see instead?

The repl crashes with the following error

node:internal/readline/emitKeypressEvents:74
            throw err;
            ^

TypeError: Cannot read properties of null (reading 'start')
    at findExpressionCompleteTarget (node:repl:1722:68)
    at REPLServer.complete (node:repl:1487:55)
    at REPLServer.completer (node:repl:792:5)
    at showCompletionPreview (node:internal/repl/utils:233:10)
    at showPreview (node:internal/repl/utils:389:7)
    at REPLServer.self._ttyWrite (node:repl:1037:9)
    at ReadStream.onkeypress (node:internal/readline/interface:284:20)
    at ReadStream.emit (node:events:507:28)
    at ReadStream.emit (node:domain:489:12)
    at emitKeys (node:internal/readline/utils:371:14)

Additional information

It seems like the following code is responsible for the crash, somehow lastDeclarationInit is null. If it helps at all I downloaded node via fnm

node/lib/repl.js

Lines 1718 to 1724 in 5576dec

	// If the last statement is a variable declaration statement the last declaration is
	// what we can potentially complete on, so let's re-run the function's logic on that
	if (lastBodyStatement.type === 'VariableDeclaration') {
	const lastDeclarationInit = lastBodyStatement.declarations.at(-1).init;
	const lastDeclarationInitCode = code.slice(lastDeclarationInit.start, lastDeclarationInit.end);
	return findExpressionCompleteTarget(lastDeclarationInitCode);
	}

[targos]

/cc @dario-piotrowicz

[dario-piotrowicz]

Thanks for the ping @targos 🙂

Thanks a lot for the report @TheDevYellowy 🙏

Yes my code didn't account for that, I'm really sorry for the inconvenience 🙇

I've opened #59032 to fix this issue

[Grooveflow]

Thanks heaps

[intentionally-left-nil]

Is there a reason this didn't make it into the next patch? v24.4.1 still contains the bug

[kidonng]

@intentionally-left-nil https://github.com/nodejs/node/blob/main/doc/changelogs/CHANGELOG_V24.md#24.4.1

This is a security release.