This PR documents the investigation of microsoft/TypeScript#62549 and confirms that the change has already been successfully ported to the Go codebase.

Background

PR #62549 "Consistently resolve to the errorType on arguments with error" modifies the TypeScript checker to pass ignoreArrowFunctions: true when checking if arguments is used in a property initializer or class static block. This ensures that arguments inside arrow functions within property initializers resolves to errorType (displaying as type any), making the behavior consistent.

Interesting Discovery

The change from PR #62549 was actually ported to the Go codebase before it was merged into TypeScript!

Timeline

• Oct 5, 2025: @Andarist opened PR #1828 to port arguments should not be allowed in class static block TypeScript#48172 (which added the ignoreArrowFunctions parameter)
• In PR Port "arguments should not be allowed in class static block" #1828: The Go implementation already passed ignoreArrowFunctions: true for the arguments check
• Oct 5, 2025: @Andarist opened microsoft/TypeScript#62549 to make TypeScript match the Go behavior
• Oct 5, 2025: PR #62549 was merged into TypeScript

As noted in the PR #1828 review:

"this has some seemingly unwanted diffs but I think this is basically desired and I opened a PR to Strada to close this gap: microsoft/TypeScript#62549"

Current State

The equivalent change is already present in the Go codebase at internal/checker/checker.go:10599:

if c.isInPropertyInitializerOrClassStaticBlock(node, true /*ignoreArrowFunctions*/) {
    c.error(node, diagnostics.X_arguments_cannot_be_referenced_in_property_initializers_or_class_static_initialization_blocks)
    return c.errorType
}

Verification

• ✅ All tests pass
• ✅ The specific test argumentsUsedInClassFieldInitializerOrStaticInitializationBlock passes
• ✅ The testdata baseline shows the correct behavior (returning any type instead of IArguments for arguments in arrow functions within property initializers)

Conclusion

No code changes are needed. This PR adds documentation (PR_62549_PORT_STATUS.md) to record that the change has been successfully ported and is functioning correctly. In fact, the Go port led the way, and TypeScript followed!

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