Change the warning statement for unused result from expression

[fluffybeing]

Resolves SR-5983.

[huonw]

Thanks!

The compiler also has tests for diagnostics like this, using directives like expected-warning {{...}} and expected-error {{...}} to tell the testing harness that the compiler should emit a specific message attached to the line with the comment (or, with expected-warning @number on the line number before or after). There's a few tests that look for this one, could you update them too?

test/attr/attr_discardableResult.swift
152:  a() // expected-warning {{result of call is unused, but produces 'Int'}}

test/ClangImporter/objc_parse.swift
217:  // expected-warning @-1 {{result of call is unused, but produces 'Unmanaged<AnyObject>!'}}

test/Constraints/diagnostics.swift
340:f8(10)          // expected-warning {{result of call is unused, but produces 'Int'}}

test/expr/expressions.swift
674:  fn(&n, 12) // expected-warning {{result of call is unused, but produces 'Int'}}

test/Parse/recovery.swift
131:  } while { true }() // expected-error{{missing condition in a 'while' statement}} expected-error{{consecutive statements on a line must be separated by ';'}} {{10-10=;}} expected-warning {{result of call is unused, but produces 'Bool'}}

[CodaFi]

Nit: You may not necessarily be calling a function if this is emitted, you may be calling a closure.

I think you can probably delete this and just use expression_unused_result_call if it's all the same.

[fluffybeing]

@CodaFi I will update it. I think the explicit information will be good and so I will go with your first suggestion.

[fluffybeing]

@huonw thanks for the help. Also, I was curious that how can I run the test locally. Wasn't able to figure out from the documentation.

[fluffybeing]

@huonw am I missing something? or this PR is ready for acceptance.

[CodaFi]

This is not quite what I was pointing out - not everything this diagnoses is a call to a closure, nor is everything it diagnoses a call to a function. So you have two options:

1. Conditionalize this diagnostic on whether the called value is a closure or a function.
2. Just delete it and use expression_unused_result_call instead.

I really recommend #2. This diagnostic seems genuinely superfluous.

[fluffybeing]

@CodaFi Thanks for the context. I thought it is just for closure and I will also not prefer conditionalizing it. I will update it then.

[CodaFi]

This was addressed by #16059. Thanks!