Go: Expose whether functions are variadic in their pp() output

[smowton]

This avoids our having types that are distinct both in the database and are distinguishable in QL, but which pretty-print identically.

[mbg]

LGTM, seems like a sensible change. One suggestion for improvement, if you are so inclined: perhaps it would make sense to put the [variadic] inside the func( ... ) part, rather than after the return types?

[owen-mc]

Good catch. Why not copy how being variadic is normally shown in go signatures, i.e. func(...interface { }) int, error? It's a bit more involved to remove the [] from the last parameter type, but it would be easier for everyone to understand (who is familiar with go).

[owen-mc]

Suggested change

	exists(string suffix | (if this.isVariadic() then suffix = " [variadic]" else suffix = "") |
	result =
	"func(" + concat(int i, Type tp | tp = this.getParameterType(i) | tp.pp(), ", " order by i) +
	") " + concat(int i, Type tp | tp = this.getResultType(i) | tp.pp(), ", " order by i) +
	suffix
	)
	result =
	"func(" +
	concat(int i, Type tp, string prefix |
	if i = this.getNumParameter() - 1 and this.isVariadic()
	then
	tp = this.getParameterType(i).(SliceType).getElementType() and
	prefix = "..."
	else (
	tp = this.getParameterType(i) and
	prefix = ""
	)
	|
	prefix + tp.pp(), ", " order by i
	) + ") " + concat(int i, Type tp | tp = this.getResultType(i) | tp.pp(), ", " order by i)

This implements printing "...interface{ }" as I suggested in my previous review.

[owen-mc]

I guess you could also keep the [variadic] to highlight variadic functions.