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support type hints; make metadata coherent

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The reader expanded ^X form to (with-meta form X), which evaluated the tag (so
^String errored 'Unable to resolve symbol: String') and, as a param, was no
longer a bare symbol (so the arg bound to nil). Now a keyword/symbol/string hint
on a symbol attaches to the symbol's :meta and the symbol stays bare, so type
hints are transparent in params, lets, and bodies. Map metadata still uses a
runtime with-meta form.

meta now returns a symbol's :meta, and def applies the name's metadata
(^:dynamic, ^:private, ^Type tag, ^{:doc}) to the var, so (meta (var x)) is
consistent. Specs in metadata-spec; grammar note in the ebnf.

README notes regex \p{...} as unsupported (separate from this).
This commit is contained in:
Yogthos 2026-06-06 00:36:10 -04:00
parent f749ec3c19
commit 761a2b8f72
8 changed files with 94 additions and 39 deletions
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18
test/spec/metadata-spec.janet
View file

@ -9,3 +9,21 @@
["vary-meta" "{:a 2}" "(meta (vary-meta (with-meta [1] {:a 1}) update :a inc))"]
["meta reader ^" "{:tag :int}" "(meta ^{:tag :int} [1 2])"]
["with-meta on fn ok" "true" "(fn? (with-meta inc {:a 1}))"])
(defspec "metadata / type hints"
# ^Type / ^:kw / ^"str" on a symbol attach as metadata and are otherwise inert:
# the symbol stays a symbol so hints are transparent in every position.
["type hint on param" "\"hi\"" "(do (defn f [^String s] s) (f \"hi\"))"]
["type hint, extra params" "[1 2]" "(do (defn g [^String x y] [x y]) (g 1 2))"]
["type hint in let" "6" "(let [^long x 5] (inc x))"]
["type hint in body" "2" "(let [s \"ab\"] (count ^String s))"]
["type hint in destructure" "3" "(let [{:keys [^long a]} {:a 3}] a)"]
["symbol hint -> :tag" "\"String\"" "(:tag (meta (read-string \"^String x\")))"]
["keyword hint -> true" "true" "(:foo (meta (read-string \"^:foo x\")))"])
(defspec "metadata / def metadata"
["^:dynamic var binds" "9" "(do (def ^:dynamic *d* 1) (binding [*d* 9] *d*))"]
["^:private on var" "true" "(do (def ^:private pv 1) (:private (meta (var pv))))"]
["^Type tag on var" "\"String\"" "(do (def ^String tv \"a\") (:tag (meta (var tv))))"]
["^{:doc} on var" "\"hi\"" "(do (def ^{:doc \"hi\"} dv 1) (:doc (meta (var dv))))"]
["(def name doc val) doc" "\"d\"" "(do (def dd \"d\" 5) (:doc (meta (var dd))))"])

16
test/unit/reader-test.janet
View file

@ -83,11 +83,19 @@
(assert (deep= @[(sym "deref") (sym "x")] (parse-string "@x"))
"deref shorthand")
# Metadata
# Metadata: a keyword/symbol/string hint on a symbol attaches to the symbol's
# :meta and keeps it a bare symbol (so type hints are transparent everywhere).
(let [form (parse-string "^:meta x")]
(assert (array? form) "metadata is array")
(assert (deep= @[(sym "with-meta") (sym "x") :meta] form)
"metadata form"))
(assert (and (struct? form) (= :symbol (form :jolt/type))) "meta-hinted symbol stays a symbol")
(assert (= "x" (form :name)) "symbol name preserved")
(assert (= true (get (form :meta) :meta)) "keyword hint -> {kw true}"))
(let [form (parse-string "^String s")]
(assert (= "s" (form :name)) "type-hinted symbol name preserved")
(assert (= "String" (get (form :meta) :tag)) "symbol hint -> {:tag name}"))
# Map metadata on a symbol still uses a runtime with-meta form.
(let [form (parse-string "^{:doc \"d\"} y")]
(assert (and (array? form) (struct? (first form)) (= "with-meta" ((first form) :name)))
"map metadata -> with-meta form"))
# Comments (skip to end of line)
(assert (= 42 (parse-string "; comment\n42"))