swiftlang/swift

[SR-5984] Error message for accidentally calling function in #selector(foo()) could suggest removing parens

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#48,543 opened on Sep 26, 2017

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Description
Previous ID SR-5984
Radar rdar://problem/34640740
Original Reporter @huonw
Type Bug
Status In Progress
Resolution

Swift 4.0
Votes 0
Component/s Compiler
Labels Bug, DiagnosticsQoI, StarterBug, TypeChecker
Assignee None
Priority Medium

md5: 939952c8851f309540d6ce3aaa7d7c15

Issue Description:

import Foundation

class Foo {
    @objc func foo() {
        _ = #selector(foo())
    }
}

call-selector.swift:5:13: error: argument of '#selector' does not refer to an '@objc' method, property, or initializer
        _ = #selector(foo())
            ^         ~~~~~

This is close to the correct syntax (#selector(foo)) and the compiler could help guide the user to this. This probably comes up most often with selectors for methods with no arguments (https://bugs.swift.org/browse/SR-1016).

Contributor guide

Research direction
Examine the Swift compiler's diagnostic system for #selector errors. Locate the code that generates the current error message (argument of #selector does not refer to an @objc method). Modify it to detect when the user has accidentally included parentheses in the selector reference and suggest removing them. This likely involves changes in the type checker or Sema phase.
Tech stack
None
Domain
compilers
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Swift
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
80