[SR-226] Implement warning about the use of C-style for loops in Swift 2.2

[DougGregor]

Previous ID	SR-226
Radar	None
Original Reporter	@DougGregor
Type	Task
Status	Resolved
Resolution	Done

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Task
Assignee	@gregomni
Priority	Medium

md5: 059d6db82e39ab1b799b6c27509640a5

Issue Description:

Per

https://github.com/apple/swift-evolution/blob/master/proposals/0007-remove-c-style-for-loops.md

we should implement a warning in Swift 2.2 that informs users that C-style for loops are going away.

[DougGregor]

Bonus points for recognizing idiomatic C-style for loops that could trivially be rewritten as for-in loops and providing a Fix-It to help with migration. For example:

for var x = 0; x != n; ++x { ... }

could be migrated to:

for x in 0..n { ... }

when x isn't written to.

[gregomni]

I've been doing some diagnoses fixing recently and getting somewhat familiar with this area. Would be happy to take this on, if no one else has code in the works.

[gregomni]

Still need to clean up the fix it ranges, but here's most of it: <https://github.com/apple/swift/pull/552\>.