The functions for retrieving, replacing, and inserting values into values all assumed they get the complete
column path as regular tagged strings. This commit changes for these to accept a tagged values instead. Basically
it means we can have column paths containing strings and numbers (eg. package.authors.1)
Unfortunately, for the moment all members when parsed and deserialized for a command that expects column paths
of tagged values will get tagged values (encapsulating Members) as strings only.
This makes it impossible to determine whether package.authors.1 package.authors."1" (meaning the "number" 1) is
a string member or a number member and thus prevents to know and force the user that paths enclosed in double
quotes means "retrieve the column at this given table" and that numbers are for retrieving a particular row number
from a table.
This commit sets in place the infraestructure needed when integer members land, in the mean time the workaround
is to convert back to strings the tagged values passed from the column paths.
The original purpose of this PR was to modernize the external parser to
use the new Shape system.
This commit does include some of that change, but a more important
aspect of this change is an improvement to the expansion trace.
Previous commit 6a7c00ea adding trace infrastructure to the syntax coloring
feature. This commit adds tracing to the expander.
The bulk of that work, in addition to the tree builder logic, was an
overhaul of the formatter traits to make them more general purpose, and
more structured.
Some highlights:
- `ToDebug` was split into two traits (`ToDebug` and `DebugFormat`)
because implementations needed to become objects, but a convenience
method on `ToDebug` didn't qualify
- `DebugFormat`'s `fmt_debug` method now takes a `DebugFormatter` rather
than a standard formatter, and `DebugFormatter` has a new (but still
limited) facility for structured formatting.
- Implementations of `ExpandSyntax` need to produce output that
implements `DebugFormat`.
Unlike the highlighter changes, these changes are fairly focused in the
trace output, so these changes aren't behind a flag.
