swiftlang/swift

[SR-1019] Can't use the new #selector syntax for generic types

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#43,631 opened on Mar 22, 2016

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bugcompilergood first issue

Description
Previous ID SR-1019
Radar None
Original Reporter JamieWhite (JIRA User)
Type Bug

xcode 7.3
Swift 2.2
Votes 2
Component/s Compiler
Labels Bug, StarterBug
Assignee None
Priority Medium

md5: 5685a8e13e6f20612a2c6754c850cfe2

Issue Description:

I have an example here: https://gist.github.com/JamieWhite/72e0f7406a33d8e52657/51032655f639d9f92042ed7c02d0ee6c9e22790f

You'll notice this:

addTarget(trampoline, action: #selector(ActionTrampoline.action(_:)), forControlEvents: events)

ActionTrampoline is generic type. How this should work is doing this:

addTarget(trampoline, action: #selector(ActionTrampoline<Self>.action(_:)), forControlEvents: events)

How I worked around this was typeAliasing ActionTrampoline<self> and using that in the #selector like this:

https://gist.github.com/JamieWhite/72e0f7406a33d8e52657/fb010c8c0403725e431880b9dc6253dafc0c3b35

Contributor guide

Tech stack
swift
Domain
tooling
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
5
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
over 1 week
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
Swift genericsSwift compiler architecture
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
25
Research direction
The issue involves a bug in the Swift compiler's handling of the #selector syntax with generic types. Look at how the compiler resolves #selector expressions in lib/Sema/ or lib/Parse/. The provided gist demonstrates the expected behavior and a workaround using a typealias. Investigate the AST nodes for #selector and the type checking logic for generic type parameters in selector expressions.