Doesn't add much logic, only takes advantage of parser structure for the ordering enforcement.
Note import_nonexistent tests should probably fail, but writing import tests needs a chain of functionality, and I figured I'd just start adding some to validate the syntax (not adding existent imports because that'd require multi-file structure).
* more tests of tuples, especially mixing positional and explicit field names
* test of match with nested tuple
* Update executable_semantics/testdata/fun_named_params2.6c
Co-authored-by: Geoff Romer <gromer@google.com>
Co-authored-by: Geoff Romer <gromer@google.com>