Three defects, all from lifting every def initialiser, none of which the
suite caught:
A def typed fresh into a live session came up zero and stayed zero. The
image flan_dev_global copies on the allocation is the only value a new
global ever gets — the host's .init-globals never calls its initialiser —
and both backends chose that image with Tast.const_init, which a def's
lifted Call fails by construction. Emit.initial_image reads the constant
back out of the lifted body; the x86 twin had the same bug.
Changing a global between def and defonce was silently ineffective: the
guard lives in the startup function compiled into the host, which a reload
cannot republish. Session.compatible refuses both directions and says to
restart; editing the value stays allowed.
And global/<n> no longer leaks into the signature refusal when a def is
retyped — the global loop names the same fact in words a reader can act on.
flan check prints def, defonce or defconst off grerun; (defvar) with no
arguments names the shapes rather than offering (defonce ); the docs,
plan.org, runtime comments and valgrind.supp are swept; BUILT.md states
the release-build cost and the uninit caveat.
Session hands global/<n> to the redefinition when a def is re-evaluated,
and that target is not a sibling — its fparent is the global — so its cell
declaration comes from Emit.redefinition's targets pass, a path no test
compiled: the dev-rerun leg runs on x86 merged, which reaches host cells
through the GOT and never needed the declaration. reload.flan carries a
(def paint i64 7) now and test_reload greps the module text for the cell
extern and the hidden body, which is the idiom the file already uses.
The trio the author decided on 2026-09-20 is now all built: def is CL's
defparameter — its initialiser runs on every daemon re-run, unguarded, so
an edited initialiser repaints the same storage on C-c C-c plus re-run —
defonce (Clojure's name for CL's defvar, per the author) initialises once
behind the .init~once. flag, and defconst stays the image.
One parse arm reads both forms; the difference is Ast.reinit, carried to
Tast.global's grerun. Emit.startup_plan gives a def no guard flag, and
Check.check_global lifts every def initialiser — zero and literal
included — into global/<n>, so the host's startup reaches it through the
function cell and a re-evaluated def swaps it (Session's def_inits;
Emit.redefinition declares the cell for a non-sibling target). The old
defvar spelling is refused with the rename and both compiling spellings,
and every program, test, doc and editor list is swept — except sand.flan,
the author's live WIP, whose seven defvar lines are flagged in FIX.org
and keep its three dependent tests red on this branch.
The wait recognised one kind of stop and waited five seconds for all the
others, then said the program was not reaching a frame boundary — on a reply
that named the condition two fields along.
Which stop is the thunk's is decided by the agent's stop generation rather
than by the condition's name, so a break entered on the same class as the one
it was evaluated inside is still told apart from it. A (pause) is answered as
a (pause) wherever it came from, the flag having never been what made one
deliberate.
A fixed array does not decay to a slice at a call, so passing one to a
function over [$t] meant writing (slice a 0 (len a)) at every call site.
(slice a) is the whole of it now and (slice a n) is the tail from n, filled
in by check.ml into the three-argument form: same node, same static bound
checks, same runtime trap, and on a fixed array the implicit length is the
constant (len a) already folds to. Neither backend grew an arity case. A
target that is not already a name goes through a slot first, so (slice (f x))
calls f once.
at and slice also reach a string, because (bytes s) was the only route to a
byte and it is about to start copying. (at s i) is the byte, bounds-checked;
(slice s ...) at all three arities answers a string viewing the same bytes,
not a [u8], which would be a writable-looking view of storage the program
does not own.
Neither is a place, and the refusal lives in [indexed] rather than in
check_place, which is the part that matters. There are three routes to a
Pindex and they share no code: check_place, the single-index set arm that
checks its own target, and addr. Asked in check_place, the question is
answered for two of them and missed for the one a person writes — a store
into a string literal compiled, and the backends disagreed about it. So
[indexed] takes a ~place location and asks at every dimension, because
(at g 0 0) over a [[2 string]] reaches the string only at the last step.
One message, and addr gets it too, so it reads as value-versus-place rather
than as a rule about assignment.
Slicing an array a call returned is refused at every arity. The view
outlives the temporary, both backends print whatever the frame reused, and
nothing traps — which was already true of (slice (mk) 0 3) and only
survivable while nobody wrote it. (slice (mk)) is short enough to become a
habit. An array literal is not this case and stays legal.
Two backend cases. emit.ml's element_addr grew the String arm beside the
Slice one. x86.ml's index_len had answered None for a string — correct while
nothing could index one, and a skipped bounds check the moment something
could — and now reads the length word, so both check the same thing.
- SA_NODEFER. sigaction without it blocks the handler's own signal for the
whole handler, and here the handler is the park — it never returns. A
hardware SIGSEGV delivered while SIGSEGV is blocked is not handled: the
kernel forces the default action. Fault, park, eval something at the
break loop that faults, daemon gone, exactly the author's session one
level in. Measured both ways; flan_crash_entered is cleared before the
hook so each break-loop fault still gets its line, and the case is pinned
(trap_park ~refault:true), confirmed to fail without the flag.
- Scope the handler to the thread it was armed on. A disposition is per
process and a merged dev session is one process, so this was shadowing
OCaml's SIGSEGV handler — and Stack_overflow — for the daemon's whole
life. Other threads chain to what was installed before. Arming per run
would leave the parked prompt's evaluations unprotected, since those are
program code too; the comment says so. Also makes the per-thread
sigaltstack honest.
- Sweep dyn-view.flan and string-eq.flan, which dev-loop added after the
first sweep. string-eq:46 wanted the aliasing outright: its comment is
about two slices sharing a base pointer.
- A StorageExhausted row for bytes, asserting the retry copies once and
whole rather than re-evaluating its argument.
- Gate the flan_dev_crash_enable declare to dev builds, so this lane adds
no dev-only text to a release module. flan_bytes_dup stays ungated: a
release build really calls it.
- Guard the section for wasm32, which compiles this file and has no
signals.
The INSERTIONSORT crash, all three rulings (FIX.org 2026-09-20):
- (bytes s) allocates a writable copy through the allocator surface —
context or (bytes s a), StorageExhausted with retry, a registry note in
dev builds (flan_bytes_dup, lowered like vec-new). (bytes-view s) is the
old zero-cost reinterpret, renamed, read-only by convention; every
in-repo reader swept over to it. (string b) unchanged.
- String constants were already read-only on both backends at -O0; now
pinned — bytes-copy.flan rows on LLVM/-O0/--x86, and dies_segv rows
asserting the write-through-view trap on both backends.
- A dev build installs a SIGSEGV/SIGBUS handler by the same dev-only
constructor slot that arms the registry: one line naming the address and
the innermost frame, then the trap-hook park — stopped, not dead, the
daemon serving. No agent: message and re-raise. Release builds untouched.
Pinned by trap_park over dev-segv.flan.
Five fixes off the independent review, plus the author's u8 ruling.
x86 parity: the bad-index block always ran x86 (it is flan dev's
default) and now says so with an explicit --x86; the condition render
gets an assertion under the x86 backend too, beside the LLVM one, and
a user error is pinned as carrying no site on both.
ArithError's layout is now pinned: {i32 op; i64 lhs, rhs} in C against
the prelude's defstruct, read field by field through the break loop's
render, driven from the editor through a divide under a restart-case.
That also covers condition and site on LLVM.
Three refusals that were wrong: trap_site tested the prefix "err"
and so ate any site whose path began with those letters; source_line
let Sys_error from input_line escape and take the whole break reply
with it, leaking the handle; and a condition with no fields was
reported as a name no struct has. The daemon now sends its own field
count and the buffer tells the two empties apart.
Nits taken: an over-long site is dropped rather than silently
truncated into a plausible one; the caret pads with the source line's
own tabs; the headline says when it has cut the field list;
flan-cnr-layout is live again as the single spelling of that request
rather than dead beside an inlined copy.
And the ruling: a u8 renders as 97 (\a) where a person is inspecting
and stays 97 where the program is printing.
A break nested inside a trap's break — a fix candidate evaluated at a
bounds stop raising its own error — copied the outer trap's site into
its snapshot, which is a caret pointing at an unrelated line under the
inner condition's name. snap_push now consumes the global: each
snapshot owns its copy, a nested entry that set no fresh site gets
none, and the outer break keeps its own. Pinned end to end.
The fields section says why the values are missing once, above the
rows, instead of repeating the sentence per field; a row keeps its own
reason only when it has one (no printer for its type).
strip_rebind and shown_names get direct coverage, including the clean
strip a real frame almost never reaches.
A full pass on the break-loop display, off a dogfooding session that
met a BoundsError and read design notes instead of values.
The headline now carries the condition's own fields — BoundsError
reads as 'low 648, high 648, length 100' with nothing special-casing
it — over one short status line, and under it the trap's own site with
the source line and a caret at the column, Elm-style. Fields render
with values through the new condition op, falling back to the layout
with one sentence per missing value.
Every choice goes out by restart-at now, so a shadowed restart is
takeable rather than refused, and its line says only whose name it
repeats. The abort line says what abort does. The bracketed
implementation notes are gone from every string that could print, and
a fixture pins that as a property of the rendering.
The break loop used to discard the pointer it was handed, so the buffer
could name a BoundsError's fields and never show 648. Now the snapshot
stashes it, flan_agent_condition hands it back on the stopped thread,
and a daemon-built thunk — locals pointed at the condition — renders
each field. Delivered at-stop, so a resume-and-restop cannot get the
old type read over the new pointer.
The trap sites publish their loc around the hook call, the snapshot
copies it, and break answers :site with the line's text as :source —
the frame lines say where each call was; this is the only record of
the indexing itself.
Compiler temps are hidden from the locals listing rather than refused
as s4; a shadowing rebind strips its ~N except where the outer binding
is on the same list, where both keep their raw spelling.
Arguments print in order with a single space between each pair, println
ending the line; (println) is the newline alone and (print) is nothing.
The checker's arm renders each argument exactly as it did alone, so typed
and dyn values mix in one call, one-argument sites are byte-identical, and
an unprintable argument is still refused at its own span.
Key members are :key-r, :key-space, :key-left-shift; MouseButton members
are :mouse-left through :mouse-back — mouse- over button- because gamepads
have buttons too. Bare members collided across enums and with user code.
The bindings enum directive grew an optional third column declaring the
Flan-side member prefix, stripped before the C prefix is applied, so key-r
checks against KEY_R rather than KEY_KEY_R; a member that does not carry
the declared prefix is reported, not checked under a guessed name. The
enum-member error grew a did-you-mean: one edit away, or the bare name of
a prefixed member, so :r suggests :key-r.
sand.flan is the author's live WIP and is deliberately not touched; its
three keywords (lines 161-166) leave test_session and sand-headless red
until he moves them. Everything else that calls the two enums moved.
A narrower scalar at a $t a slice already fixed widens into the fixed
type — the same cast a monomorphic parameter applies — where the old
rule refused both directions. One accepts pin, one runtime line in
int-generic.flan, and the web page's predicate table catches up: five
predicates, integer? at the head, and the entailment chain grown one
link.
The fifth predicate: integer? admits every integer kind and no float,
entails numeric? (and through it ordered? and equal?), and gates what
only integers support — the bitwise fold asks for it, the shifts admit
a bounded variable under it, and the float literal in an integer? body
is refused in the bound's own words. The literal arm needed nothing:
the entailment admits an integer constant under either bound.
abs-i32 and abs-i64 collapse into one integer?-bounded generic whose
i32/i64 copies even keep the old symbols; abs-f32/abs-f64 stay as the
float spellings because the right float abs is a sign-bit clear no
integer body spells, and (abs 1.5) now refuses naming the bound — the
where clause is checked before the name-collision check, which used to
answer that call with 'abs-f64 is already defined'.
Mixed widths at one $t join at the wider type now, in either argument
order — the author reversed the refuse-both rule on 2026-09-20. A
joinless pair is deferred and re-asked against the final binding, so a
later wider argument settles u32-vs-i32; u64-vs-i64 still refuses, and
a container-bound variable still binds exactly. The out-widened
arguments catch up through the ordinary Cast.
Two review follow-ups folded in: a struct field's unknown-lowercase
message stops suggesting a parameter vector it does not have, and the
tyvar-at-dyn message says defgeneric/defmethod in words instead of a
schematic that does not compile.
(array-gen [3 4] (fn [i j] ...)) — the canonical form — was refused:
check_fn saw no (Fn ...) want and no position to take types from. But the
form knows them: one i32 index per dimension is the rank's own promise.
check_array_gen now hands an inline fn its parameter types directly, with
the annotated element type as the return want where the annotation reaches
that deep, and the return left for the body to say where it does not — so
a bare inline fn infers its element type the way a fill value does, and a
body that disagrees with an annotated element is reported at the
generator's answer, per element. Named defn generators check as before.
check_fn grows a ?gen way in for exactly this: parameter types without a
Fn want, return optional. An inferred-return body sees Unit as ctx.ret, a
rough edge left rough on purpose.
Pins: inline at rank 1 and 2, inferred element, annotated defvar, the
per-element mismatch, inline arity. The acceptance program gains the
inline form, a struct-valued fill (the per-element store is a struct
copy), and evaluated-once (a counting fill value called one time for four
elements) — riding the three existing rows, no new ones. And the FIX.org
entry the pass never wrote: dims by the [n T] rule, one index per
dimension, the Zero+While/Set/Pindex lowering with no backend edits,
composition by nesting the forms, and this fix.
MANUAL.md: *flan* and *flan-repl* throughout, the REPL's output and
error-summary behaviour, the two clears on C-c C-o / C-c M-o, the
diagnostics buffer as the one list with the memory section below the
errors, and the settings table without flan-output-buffer. BUILT.md's
three mentions of *flan-output* updated to the routing that exists.
FIX.org records the decision, dated.
*flan-output* is gone. The program's output lands in the daemon's buffer
always — renamed *flan-dev* to *flan* — and at the REPL when one is open,
inserted above the prompt, output first and the value after it. A
rejection puts its message in *flan-diagnostics*, which now pops up, and
leaves one line at the prompt pointing there; the diagnostics buffer got
a major mode of its own, read-only with n/p/RET, and the memory sites
from flan-check-memory render into it as one section below the errors,
replaced whole on every ask. Two clears at the REPL, on CIDER's keys:
C-c C-o for the last send's output, C-c M-o for the transcript.
No daemon changes: output already rides every reply's :output, so both
destinations are editor-side routing.
The spike banner names plan.org's Types section and spec-memory.md's
Generics section as the current account. Neither said anything about a
literal at a type variable, about widening meeting a generic binding,
or about dyn, and all three are now observable from a program -- so
the account had a hole rather than an error. Filled, in
spec-memory.md, in the terms a programmer meets them in.
And one stale claim found and deliberately left: plan.org still lists
five predicates and describes copyable? and move-only-by-default at
length. spec-memory.md already records that copyable? went with the
second repeal and check.ml has four. That sentence belongs to the
ownership-repeal lane, so it is flagged in FIX.org rather than
rewritten here.
The two compositions the milestone owed, pinned, and the record of the
whole lane.
A package whose exports are generic: pkgs/gen, imported by
pkg-generic.flan at three shapes. One generic at two element types.
One that calls another in its own package at its own variable, so the
transitive copy is generated from a call site two files away. And a
generic written in the program calling one written in the package at
its own $t, which only resolves once Load has flattened both bodies
into one namespace -- the thing that has to change the day a package
becomes a real compilation unit, because a copy is made from a body
and a body that did not cross cannot be copied. Plus the call-site
half of a bound written in another file, quoted here rather than
pointed at in a file the caller cannot change.
And the composition with the widening trial. A binary operator
re-checks its right operand at its left one's type inside a trial, so
a generic call written there is checked twice and once thrown away.
The discarded pass's instantiation does not go back out: instantiate
rewinds a copy whose *body* refused, which is a different event. It
does not have to, and the reason is this lane's own rule rather than
luck -- a generic call's instantiation is read off its arguments and
never off the ambient want, so both passes ask for the same types and
the second ask is a cache hit. Pinned by counting the copies in the
checked program.
The widening lane's note said that cache already rewinds itself. It
does not. Corrected in the comment and in FIX.org, in place.
The refusals generics obsoleted, swept. Every message that sent
somebody to a schedule now says what is actually true of the thing in
front of them.
An unknown lowercase type name used to be reported as unimplemented
generic code over a type variable. Generics are implemented, and
resolve_name consults env.tyvars and env.subst long before anything
reaches that arm -- so a lowercase name arriving there is a typo too
far from any type to guess at, or a type variable nobody introduced.
The sentence names the sigil that would introduce it.
A capitalised name given type arguments is the other half, and it is
still genuinely unbuilt: Types.Named is a bare string with no room for
parameters, and giving it some is a change to Types.t and therefore to
the layout calculator, both backends, Render and DWARF. Both sites
that reported it -- the type resolver and the value-position fork --
now say a generic *type* is not there yet and point at the generic
function that is.
Plus the prelude's side of it. pos?, neg? and zero? are three
questions about a number's sign, one body each, answering at every
numeric type -- the family the whole feature was asked for, and the
one thing the landed generics could not write until a literal was
allowed to stand at a bounded type variable.
Two collapses examined and declined, with the real reason written
where the old one was. abs stays per width because numeric? is the
only bound that admits a written 0 and it admits floats too, and the
integer body is the wrong abs for a float: it hands back a negative
zero. It waits on an integer? predicate, which is language surface.
min and max stay builtins because they are variadic and slot each
operand so it is evaluated once; a binary prelude generic would put
the double evaluation back at the call site. Their generic half was
never missing -- ordered? already admits them in any body that
declares it.
Nothing stopped a type variable being instantiated at dyn, because dyn
is an ordinary case of Types.t and substituted like any other type. The
copy was then made and walked into the dyn answers that are not all
there, and the refusal arrived from inside the generic's own source:
(or-else (Some d) e) over two dyns was reported against <prelude>:385,
a line the caller did not write and cannot act on.
Refused at the binding instead, where the call site is. The message
does not only say no: two models answer "one body, many types" here
and they are not rivals -- this one copies per written type at compile
time, defgeneric/defmethod dispatch at run time on a value that
carries its own -- so a dyn argument is asking the second question of
the first machinery, and the sentence names the other spelling.
Only the unbounded half is new. A variable carrying a {:where} clause
was already refused, because pred_holds says no to dyn for all four
predicates, and that refusal is left in front of this one on purpose:
it names the predicate the signature wrote down, which is the more
specific of the two answers.
Whether dyn should eventually flow through a generic is the author's
call and is recorded as open. Refusing now is the direction that can
be walked back: allowing it later adds programs, and nothing written
under this rule stops compiling.
Implicit widening landed after generics did, and the rule the two of
them left between them read off the order the arguments were written
in. (eq2? i8 i64) was refused, because $t bound to i8 and i64 into i8
can lose. (eq2? i64 i8) was accepted, because $t had already bound to
i64 and the i8 widened into the want that substitution had made
concrete. Same two values, same function, one copy at i8 refused and
one copy at i64 generated.
Neither answer was unsound -- a widen cannot change a number -- so
this is not a bug report, it is a decision that was never taken.
Taking it: implicit widening does not cross a generic binding. A
concrete argument at a variable an earlier argument already bound has
to be that type, and both orders now refuse with the same sentence,
naming the binding, the argument, and the cast to write.
Refusing is the direction that can be walked back. Letting the pair
join at the wider type is a coherent rule too, and it can be added
later without invalidating a program written under this one; the
reverse is not true.
The rule costs almost nothing because Types.widens_to admits only
numeric scalars. A variable bound inside [$t] or (Fn [$t $t] bool)
leaves a parameter no widening ever applied to, so sort-by and the
whole fn-literal path are untouched by construction. Two exceptions
keep the ergonomics: an untyped literal has no type of its own to
keep, so it still takes the variable's; and a form with no type
without a want -- (zeroed) -- is asked for its natural type through a
trial, and falls back to the want it always had when the trial
refuses.
pos? over every numeric type from one definition was the motivating
example for milestone 5 and was the one thing the landed generics could
not write: (> x 0) refused with "expected t, found the integer literal
0", because int_literal had no arm for a want that is a type variable.
It has one now, and the bound is what makes it sound rather than
optimistic. Every type numeric? admits is an integer or a float, and an
untyped integer constant is usable at all of them, so there is no
instantiation of a numeric? variable at which the literal has no
meaning. Under a weaker bound there is -- ordered? admits an enum -- so
numeric? is what is asked for and the refusal names it.
The float literal is refused at a type variable even under numeric?,
and that asymmetry is the concrete arms' own: an integer constant is
usable where a float is wanted and a float literal is never usable
where an integer is wanted, so a body written with 0.5 has no meaning
at the integer half of its own bound. Refusing at the definition is
what the abstract pass is for; the alternative is a surprise at
whichever call site first asks for i32.
The node the abstract pass builds is never emitted. Each copy
re-checks the same form with the variable substituted, and that is
where the literal is built at the concrete width and range-checked --
so (+ x 300) is fine at i32 and a refusal at u8, and u8 is where it is
refused.
A defn named after a builtin wins for its whole file, and until now that
was the end of it: the builtin had no remaining spelling, so a defn that
meant to wrap one was unbounded recursion. builtin/len is the builtin len
wherever it is written, shadowed or not.
The qualifier is the package one's, and builtin is reserved rather than
resolved: Load refuses it as an import alias, Check refuses it as a
declaration's name, and those two doors are the only ways a qualifier can
be made. named_call and var each strip the prefix and re-enter with a flag
that the shadowing guard consults, so every arm below sees the bare name
and refuses in the builtin's own words.
The shadow warning now names the escape in its second half.
The bug review found: [start_on] claimed [started] at the top and every
failure exit left it claimed. Under [flan dev] the constructor is the first
caller and reports to nobody, so a path nothing could bind disarmed the
program's own (agent/start ...) as well — it answered 0 with no socket, no
listener and no hooks, where before this lane the explicit form answered -1.
Success reported for nothing at all is worse than the error it replaced.
So every way out that is not a listening socket unwinds: the fd is closed, a
file the bind managed to make is unlinked, and [started] goes back to 0 so a
later start is a real attempt. Pinned by running the zero-argument fixture
with FLAN_AGENT_SOCKET pointing nowhere — constructor fails silently, main's
own call then fails loudly, "cannot listen" and exit 1.
Two arguments to (agent/start) are refused, which nothing held: the macro's
[& args] cannot say "one at most", so what says it is the expansion splicing
every argument into a function that declares one. The message names
agent/start-at and carries the expanded-from note, and that is what the
acceptance row asserts.
And the reply a delivery gets when there is no agent in the process, which
nothing held either. dev-noagent.flan parks, so it was never this case;
dev-noagent-running.flan keeps running, and the answer is a refusal naming the
socket that could not be reached — not install_note's "queued", which would
promise a poll with nothing to drain. Which leaves that note unreachable in
all three shapes rather than merely unpinned, worked through in FIX.org.
FIX.org also now says what an exported FLAN_AGENT_SOCKET would do: start_on
unlinks before it binds, so an agent-linked program started in that
environment takes the path away from whoever bound it first.
