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The removal joins the deferred map operations in the test and in the note

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The arm was written with the others and through the same deferral, and neither
the generics row in test_flan.ml nor the paragraph in BUILT.md that enumerates
what defers had it. Its placeholder is get's, for get's reason: it answers an
(Option V), so the match around it still has to check while the key is a
variable.
This commit is contained in:
Joseph Ferano 2026-09-17 23:13:30 +07:00
parent 9f85139f1f
commit c59cc95679
2 changed files with 10 additions and 3 deletions
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7
docs/BUILT.md
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@ -5393,9 +5393,10 @@ to name and nothing to choose between, so the abstract pass could not build the
pair would have been worse than refusing: it would hash a string's pointer and a struct's padding.
**What closes it is deferral, and what makes deferral safe is the `where` clause.** `put`, `get`, `has-key?`,
`reserve` and `clone` — the five arms that reach `key_fns` — now check their arguments and then, when the key is a
type variable, return a placeholder of the operation's own type: `Unit` for `put` and `reserve`, `None` for `get`
so the `(Option V)` around it still checks, `false` for `has-key?`, a zeroed map for `clone`. The whole node is
`map-remove!`, `reserve` and `clone` — the arms that reach `key_fns` — now check their arguments and then, when the
key is a type variable, return a placeholder of the operation's own type: `Unit` for `put` and `reserve`, `None` for
`get` and for `map-remove!` so the `(Option V)` around either still checks, `false` for `has-key?`, a zeroed map for
`clone`. The whole node is
thrown away with the rest of the abstract pass, exactly as `println`'s is, and the real one is built when the copy
is checked with `$t` concrete.

6
test/test_flan.ml
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@ -2676,6 +2676,12 @@ let () =
accepts "get over a type-variable key answers an (Option V)"
"(defn f [m (Map $t i32) k $t] i32 {:where (hashable? $t)} \
(match (get m k) (Some v) v _ 0))";
(* And so does the removal, whose placeholder is [get]'s for the same reason:
it answers an (Option V), so the match around it still has to check while
the key is a variable. *)
accepts "map-remove! over a type-variable key answers an (Option V)"
"(defn f [m (Map $t i32) k $t] i32 {:where (hashable? $t)} \
(match (map-remove! m k) (Some v) v _ 0))";
accepts "and so do has-key?, reserve and clone"
"(defn f [m (Map $t i32) k $t] bool {:where (hashable? $t)} \
(do (reserve m 8) (let [c (clone m)] (free c) (has-key? m k))))";