Show signature help according to the last selected completion item

[jdneo]

fix redhat-developer/vscode-java#3127

[rgrunber]

Works for me. I've noticed we have a lot of for loops that iterate over the known signature information (See SignatureHelpHandler.signatureHelp(..)) so I wanted to make sure there wasn't a way to combine this proposed check into the one below, but it needs to verify every given entry before proceeding to the other strategy.

Maybe in the future we can look at a nicer way to perform these checks.

[jdneo]

@rgrunber Do you mean this part https://github.com/eclipse/eclipse.jdt.ls/blob/master/org.eclipse.jdt.ls.core/src/org/eclipse/jdt/ls/core/internal/handlers/SignatureHelpHandler.java#L126-L222?

[rgrunber]

Yes, but also the code immediately above the block you added in SignatureHelpUtils here. It's very low priority since I don't think there's a faster way, it's just an issue of whether it would be nicer to write those as some kind of stream() logic. Not worth it if they become more confusing though.

[jdneo]

Yes, but also the code immediately above the block you added in SignatureHelpUtils here.

I see. I can think if we can combine the two for-loops into one as well as keep the readiness.