[SR-3577] Inexistent constructor not detected at compile time

[swift-ci]

Previous ID	SR-3577
Radar	None
Original Reporter	cristianames (JIRA User)
Type	Bug

Environment

Xcode Version 8.2.1 (8C1002)
macOS 10.12.2 (16C67)

Additional Detail from JIRA

Votes	1
Component/s	Foundation
Labels	Bug, RunTimeCrash
Assignee	None
Priority	Medium

md5: 776eb9f80897a433db2c467cc820bd02

Issue Description:

For some reason that I can't explain, the class Timer seems to have an initializer with no parameters, which it doesn't had, so when you initialize a new timer using this non-existent variant, the compiler won't complain, but at RunTime there will be an EXEC_BAD_ACCESS error. I had tried subclassing, reimplementing the same class again to see if I can detect the source of the error, but I couldn't. To let clear the problem I let a snippet of code down below.
Code:

let baz = Timer()

Error: Execution was interrupted, reason:EXEC_BAD_ACCESS (Code=1, Address= 0x0)

[belkadan]

This is probably better suited to Radar, since the fix would be in the Objective-C header rather than in anything to do with Swift. @phausler, what do you think?

[phausler]

this failure is already tracked as <rdar://problem/28924710> but unfortunately I don't think there will be enough time to do so as a compiler change for swift 4?
Or are you suggesting to make -[NSTimer init] unavailable?

For reference the only valid DI for NSTimer is:

- (id)initWithFireDate:(NSDate *)date interval:(NSTimeInterval)ti target:(id)t selector:(SEL)s userInfo:(id)ui repeats:(BOOL)rep;

[belkadan]

Ah, yes, marking -init unavailable is what I meant, if it doesn't interfere with any possible private subclasses.

[phausler]

If this class were to have been written in swift in 1996 when it was written, my guess is that the original author would have slapped a final on it 😉

[Dante-Broggi]

In the Xcode 9.4.1 toolchain, `Timer` still has an `init()`, but it doesn't crash.