Confusing error on cross-module access of isolated state

[AnthonyLatsis]

Description

The message says "can not be mutated on a nonisolated actor instance" when the mutation is in fact performed on an instance of an isolated struct.

Reproduction

swift/test/Concurrency/nonisolated_access.swift

Lines 41 to 44 in 8ae66ec

	var s = S()
	s.x += 0 // okay
	// expected-error@+1 {{main actor-isolated property 'y' can not be mutated on a nonisolated actor instance}}
	s.y += 1

Expected behavior

The part of the message at issue is chosen from a list of options:

swift/include/swift/AST/DiagnosticsSema.def

Lines 5475 to 5483 in 8ae66ec

	ERROR(actor_isolated_non_self_reference,none,
	"%4 %kind0 can not be "
	"%select{referenced|mutated|used 'inout'}1 "
	"%select{from outside the actor|on a different actor instance|"
	"on a nonisolated actor instance|"
	"from a Sendable function|from a Sendable closure|"
	"from an 'async let' initializer|from global actor %3|"
	"from the main actor|from a nonisolated context|"
	"from a nonisolated autoclosure}2",

The correct option in this case appears to be "from a nonisolated context".

Environment

Swift version 6.1-dev (Swift 66d4cd1)

Additional information

No response

[Anshika9gaur]

Hi, I’m Anshika Gaur, and I’d like to work on this issue as my first contribution to the Swift project. Looking forward to contributing to the Swift project!

Thanks!

[Anshika9gaur]

Hello!

I am trying to run the nonisolated_access.swift file, but I encountered the following error:
error: no such module 'A'
It appears on the line import A. I’m wondering if this issue could be related to something I might have missed during setup, or if it’s caused by a problem with building or including module A. I haven’t made any changes to the original code apart from basic troubleshooting, and the error persists.

Could someone please guide me on how to resolve this issue or if there are specific steps required to ensure module A is correctly built or included?

Thank you very much for your time and assistance!

@AnthonyLatsis

[AnthonyLatsis]

I suspect you might be trying to run the test directly. Have you read up on Running tests?

[Anshika9gaur]

Clarification on Running Tests for Windows Setup

Hello @AnthonyLatsis,

Thank you for guiding me to the file on Running tests. After reading through it, I noticed that the instructions seem tailored for macOS (e.g., references to test-macosx-$(uname -m) paths). Since I am working on Windows with WSL, I wanted to confirm if there are equivalent steps or adjustments for my environment.

Could you please let me know if there’s a specific process or documentation I should follow for running tests in this setup?

Thank you for your time and support!

Best regards,
Anshika Gaur

[AnthonyLatsis]

FYI, this tells me that you are supposed to follow the instructions for Linux in the getting started guide.

After reading through it, I noticed that the instructions seem tailored for macOS

Yeah, we should probably use a glob pattern there. Thanks for bringing this up. The build directory names depend on the host platform, but otherwise the instructions for running tests are the same for macOS and Linux.