The current iOS binding generator only generates returns if the
function being bound does not return an error. If a second error
return type is also present, the binder always generates both the
primary as well as the error as an output parameter.
This is undersirable because most decent functions in Go will
also return errors, so all of those get converted to plain methods
iOS side, each of them requiring allocating the return variable
first and only then execute the call. This gets even more annoying
with the Swift error wrapping protocol which converts errors to
throw statements automatically, but which still needs the ugly pre-
allocs caused by the genrated bindings not returning the result,
just placing it in an output argument.
This CL changes that so that if a nullable result is being returned
by a bound method from Go, then it is generated as a proper return
and not an output argument. This allows erroring functions to still
be called as a function in ObjC, and even more elegantly drop even
the error part in Swift.
Change-Id: I35152d7d2fd2a132eba836fa23be8fd4f317f097
Reviewed-on: https://go-review.googlesource.com/34072
Reviewed-by: Elias Naur <elias.naur@gmail.com>
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