[SILGen] Make #function printing more consistent.

[rudkx]

Print parens and "_:" in cases where a function has no named
parameters.

We already print the parens in cases with no parameters, and the "_:"
for unnamed parameters in cases where there are already named
parameters.

Fixes: rdar://problem/19785368

[rudkx]

@swift-ci Please smoke test

[rudkx]

@swift-ci Please smoke test Linux platform

[rudkx]

@swift-ci Please clean smoke test Linux platform

[jckarter]

Looks good to me. This might deserve a heads up on the swift forums (if you haven't already) in case people are relying on the old behavior.

[rudkx]

@shahmishal Mishal, any idea what's going on with this Linux build failure?

[rudkx]

@jckarter Sure, I'll post a heads-up on the user forum.

[shahmishal]

@rudkx I have not seen this failure before, @mikeash have you seen this?

[jrose-apple]

That's a change from this PR. The assertion is looking for the old name and needs to be updated.

[rudkx]

@jrose-apple Ah yes, there is a real failure in the tests as well. I hadn't gotten past this:

clang: error: no such file or directory: 'tools/SourceKit/tools/sourcekitd/bin/InProc/CMakeFiles/sourcekitdInProc.dir/sourcekitdInProc.cpp.o'
03:03:24 clang: error: no such file or directory: 'lib/libSourceKitSwiftLang.a'
03:03:24 clang: error: no such file or directory: 'lib/libsourcekitdAPI.a'
03:03:24 clang: error: no such file or directory: 'lib/libSourceKitSwiftLang.a'
03:03:24 clang: error: no such file or directory: 'lib/libSourceKitCore.a'
03:03:24 clang: error: no such file or directory: 'lib/libswiftDriver.a'
03:03:24 clang: error: no such file or directory: 'lib/libswiftFrontend.a'
03:03:24 clang: error: no such file or directory: 'lib/libswiftIDE.a'
03:03:24 clang: error: no such file or directory: 'lib/libswiftMigrator.a'
03:03:24 clang: error: no such file or directory: 'lib/libswiftFrontend.a'
03:03:24 clang: error: no such file or directory: 'lib/libswiftIDE.a'
03:03:24 clang: error: no such file or directory: 'lib/libswiftMigrator.a'
03:03:24 clang: error: no such file or directory: 'lib/libswiftIndex.a'
03:03:24 clang: error: no such file or directory: 'lib/libswiftParseSIL.a'
03:03:24 clang: error: no such file or directory: 'lib/libswiftIRGen.a'
03:03:24 clang: error: no such file or directory: 'lib/libswiftSILGen.a'
03:03:24 clang: error: no such file or directory: 'lib/libswiftSILOptimizer.a'
03:03:24 clang: error: no such file or directory: 'lib/libswiftSIL.a'
03:03:24 clang: error: no such file or directory: 'lib/libswiftLLVMPasses.a'
03:03:24 clang: error: no such file or directory: 'lib/libswiftSema.a'
03:03:24 clang: error: no such file or directory: 'lib/libswiftSerialization.a'
03:03:24 clang: error: no such file or directory: 'lib/libswiftClangImporter.a'
03:03:24 clang: error: no such file or directory: 'lib/libswiftParse.a'
03:03:24 clang: error: no such file or directory: 'lib/libswiftAST.a'
03:03:24 clang: error: no such file or directory: 'lib/libswiftMarkup.a'
03:03:24 clang: error: no such file or directory: 'lib/libswiftOption.a'
03:03:24 clang: error: no such file or directory: 'lib/libSourceKitSupport.a'
03:03:24 clang: error: no such file or directory: 'lib/libswiftBasic.a'
03:03:24 clang: error: no such file or directory: 'lib/libswiftDemangling.a'
03:03:24 clang: error: no such file or directory: 'lib/libswiftSyntax.a'
03:03:24 clang: error: no such file or directory: 'lib/swift/linux/x86_64/libswiftCore.so'

[mikeash]

Those errors are apparently some weird but harmless thing that CI latches onto as "the error" when something else goes wrong. That's being tracked in rdar://problem/43165161.

[rudkx]

@swift-ci Please smoke test and merge