A defvar typed at the top of a file could not be evaluated with C-x C-e. The
key was wired straight to eval-expr, so the parser met a declaration where an
expression was required and said so: "defvar is a top-level declaration, not
an expression". The only way to get the var installed was C-c C-c. That split
was never a property of the compiler, which has had both evaluators side by
side in lib/dev.ml all along — one installs a body under a name, the other
wraps an expression in a thunk because there is no name to install into. It
was a property of the keymap.
So the key now dispatches on the form it would actually send. Two questions,
both of which have to answer yes before the declaration path is taken: the
depth at the form's open delimiter says whether anything encloses it, and the
head says whether it is a declaration. Requiring the first is what keeps an
inner expression inside a defn body evaluating as an expression — the
enclosing form being a declaration is not a reason to reinstall it, and the
cursor's position in the file was never the question. Requiring it also
leaves a defn written inside a let to the parser, which refuses it correctly,
rather than quietly installing it as a top-level definition.
The head list is spelled out in flan-dev.el and points at the arm of
Parse.expr that is its authority; package is deliberately left out of it,
because this is the set of heads that fail when sent to the expression
evaluator and not the set that introduces a name.
The echo area is now the only thing that says which evaluator ran, so it has
to say it. An expression still reports "=> 42". A declaration reports what
landed, and reports it by name: a defvar installs no bodies, so leading the
sentence with the generic label left it reading "form installed in 4 ms (also
ticks)" — the one name that changed, parenthesised as an afterthought. Where
there are no functions the names are what changed, so they are what the
sentence is about, and the aside is then empty rather than a repeat of it.
C-c C-c is untouched and stays the explicit "reload the definition I am
standing in", which is still the command to use from inside a body.
Joseph Ferano
ce3b62340b