This change revives some compiler tests that are still lingering around
from the old architecture, before our latest round of ship burning.
It also fixes up some bugs uncovered during this:
* Don't claim that a symbol's kind is incorrect in the binder error
message when it wasn't found. Instead, say that it was missing.
* Do not attempt to compile if an error was issued during workspace
resolution and/or loading of the Mufile. This leads to trying to
load an empty path and badness quickly ensues (crash).
* Issue an error if the Mufile wasn't found (this got lost apparently).
* Rename the ErrorMissingPackageName message to ErrorInvalidPackageName,
since missing names are now caught by our new fancy decoder that
understands required versus optional fields. We still need to guard
against illegal characters in the name, including the empty string "".
* During decoding, reject !src.IsValid elements. This represents the
zero value and should be treated equivalently to a missing field.
* Do not permit empty strings "" as Names or QNames. The old logic
accidentally permitted them because regexp.FindString("") == "", no
matter the regex!
* Move the TestDiagSink abstraction to a new pkg/util/testutil package,
allowing us to share this common code across multiple package tests.
* Fix up a few messages that needed tidying or to use Infof vs. Info.
The binder tests -- deleted in this -- are about to come back, however,
I am splitting up the changes, since this represents a passing fixed point.
289a0d405d