This generalizes the previously-added lint-like check for when an object
constructor is used to define an input variable and it contains a
definition for an attribute that isn't part of the target type, so that
now it also works for various nested structures that commonly arise in
real-world configurations.
Because this is now considerably more complicated I factored it out into
a new package called "lint" which could potentially grow to include other
similar "technically valid but probably a mistake" situations in future,
but for now it just introduced an opportunity to produce similar warning
messages for ignored attribute definitions in the default value for an
input variable.
It seems to me that there is actually no useful reason to include an
unexpected attribute definition in either of these two cases: that
attribute will never appear as part of any expression that any other part
of the configuration can use. Therefore I considered making these be
treated as errors rather than warnings, but turning something that was
previously valid into an error is risky so I'm suggesting that we start
with these as warnings and then consider upgrading them to errors in a
later release if we don't hear of anyone reporting a false-positive that
was _somehow_ actually useful. (I find that very unlikely, but still...)
Signed-off-by: Martin Atkins <mart@degeneration.co.uk>
