By adding an expected type to the compilation context, it is
now possible for type checking to occur on keyset expressions
and return statements at the moment that they are being compiled.
Previously, it was necessary to tentatively compile them and then
typecheck afterward.
Signed-off-by: Will Hawkins <hawkinsw@obs.cr>
Fields were not given default values when a struct was declared
without initializers.
Also, cleanup code in the helper function for binary operations
on struct instances.
Signed-off-by: Will Hawkins <hawkinsw@obs.cr>