[SR-3359] [QoI] Warn if @discardableResult used with void result.

[swift-ci]

Previous ID	SR-3359
Radar	None
Original Reporter	aaroncrespo (JIRA User)
Type	Improvement
Status	Resolved
Resolution	Done

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Improvement, DiagnosticsQoI, StarterBug
Assignee	matthew carroll (JIRA)
Priority	Medium

md5: b2778488745a5fbb25973db793f3d89c

Issue Description:

Noticed that:

@discardableResult func foo() {
  print("hello")
}
foo()

Didn't raise a warning or error when compiled. My thoughts are that it should?

[swift-ci]

Comment by aaron crespo (JIRA)

see https://bugs.swift.org/browse/SR-1553

[belkadan]

Seems reasonable.

[swift-ci]

Comment by Matthew Carroll (JIRA)

Hi @belkadan,

I'd love to contribute to the Swift project by resolving this issue. I implemented the warning mentioned above by adding a fix-it to remove @discardableResult on functions that return void. Here is the PR:
#6681

Please let me know what you think.

Thanks!
Matthew

[swift-ci]

Comment by Matthew Carroll (JIRA)

#6681