[SR-78] swiftc crushed for very simple code

[swift-ci]

Previous ID	SR-78
Radar	None
Original Reporter	windoze (JIRA User)
Type	Bug
Status	Resolved
Resolution	Done

Attachment: Download

Environment

Ubuntu 14.04.3 LTS x86_64, Ubuntu 14.04 Swift 2.2 Snapshot

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug, CompilerCrash
Assignee	@jckarter
Priority	Medium

md5: 4ce09acd58663f0925c8dc1bdf749fe1

Issue Description:

Following piece of code effectively crushes swiftc

struct A<T1, T2> {
    var f:B<T1, T2>
    var b:B<T2, T1>
    var v:T1
}
struct B<T1, T2> {}

Logs attached

[tachyonics]

Hi,

I decided to take a look at this bug so I could start getting familiar with the codebase.

I was able to reproduce the bug both on the command line and Xcode. Digging into it, it looks like this issue is caused by the code trying to increment an exhausted iterator - if I understand correctly in the case where B doesn't have any properties (so there is an iterator that starts out exhausted).

I have verified that handling the case of an exhausted iterator so the code doesn't try to increment it allows your code to compile.

I will look to add a unit test for this use case to verify that it now works as expected and then submit a pull request.

[swift-ci]

Comment by Manav Gabhawala (JIRA)

Fixed with pull request: #293

[jckarter]

Fixed in #293.