Calls compile direct (target value embedded) iff the compiling unit has
direct-linking on, the target isn't ^:redef/^:dynamic, and it's an
already-defined fn; otherwise indirect (live var deref, redefinable). Direct
emission is guarded to function values only — embedding a non-function would make
Janet evaluate it as code.
:aot-core? (init opt, default true; JOLT_AOT_CORE=0 disables) compiles the core
tiers with direct-linking on so core->core calls are direct. User/REPL code
compiles indirect by default, so redefining functions in the REPL works with no
annotation, exactly like Clojure. :aot-core? false makes core indirect too — the
whole language becomes redefinable. ^:redef / ^:dynamic on a target force it
indirect even inside a direct-linked unit.
Also fixes a pre-existing gap this surfaced: compiled def dropped ALL var
metadata (so ^:dynamic was silently lost under compilation, and ^:redef couldn't
work). def metadata now flows analyzer -> IR -> back end (new form-sym-meta host
fn, def-node :meta, var-setter-meta) and is applied to the cell.
Matrix test in test/integration/direct-linking-test.janet. Conformance 218/218
in all three modes under both :aot-core? true and false; battery holds 3916;
binary rebuilt.
a3cc035782