reader: one-char literals for non-symbol chars (\{ \( \, \%)

read-char read the char name with symbol-char?, so a literal whose char isn't a
symbol char (\{, \(, \), \,, \%, …) came back as an empty name and errored
'Unsupported character'. Now a single non-symbol char after \ is taken as a
one-character literal of that char. Surfaced by funcool/cuerdas (uses \{), which
now loads. Spec cases added.

doc/tools-deps.md

@@ -86,8 +86,9 @@ env read would be frozen at build).
   libs and reports load/run status (network-gated behind `JOLT_CONFORMANCE=1`, so
   CI stays offline). First run:
   - `medley` — loads and runs.
-  - `cuerdas` — fails to load: the reader rejects a char/literal it uses
-    (`Unsupported character: \`). A genuine reader gap to chase.
+  - `cuerdas` — now loads (it used `\{`, a one-char literal the reader rejected;
+    fixed). A function (`kebab`) still hits a separate runtime gap — a smaller,
+    per-function issue rather than a whole-namespace failure.
   - `stuartsierra/dependency` — `Long/MAX_VALUE`: JVM interop, so out of scope
     (it isn't actually pure-`cljc`).
 

src/jolt/reader.janet

@@ -314,9 +314,15 @@
 
 (defn read-char [s pos]
   # pos is at backslash; produce a char value directly (self-evaluating)
-  (let [end (read-char-name-end s (+ pos 1))
-        char-name (string/slice s (+ pos 1) end)]
-    [(char-from-name char-name) end]))
+  (when (>= (+ pos 1) (length s))
+    (error "unexpected end of input after \\"))
+  (let [end (read-char-name-end s (+ pos 1))]
+    (if (= end (+ pos 1))
+      # The char right after \ isn't a symbol char (e.g. \{ \( \, \% \" ): it's a
+      # one-character literal of that character itself.
+      [(make-char (s (+ pos 1))) (+ pos 2)]
+      (let [char-name (string/slice s (+ pos 1) end)]
+        [(char-from-name char-name) end]))))
 
 (defn read-anon-fn [s pos]
   # pos is at #, next char is (

test/spec/reader-syntax-spec.janet

@@ -12,6 +12,12 @@
   ["namespaced keyword" "true"      "(= :a/b :a/b)"]
   ["char"               "\\a"       "\\a"]
   ["char newline"       "true"      "(= \\newline (first \"\\n\"))"]
+  # single non-symbol chars are one-char literals (\{ \( \, \% etc.)
+  ["char open-brace"    "123"       "(int \\{)"]
+  ["char open-paren"    "40"        "(int \\()"]
+  ["char comma"         "44"        "(int \\,)"]
+  ["char percent"      "37"        "(int \\%)"]
+  ["char unicode"       "65"        "(int \\u0041)"]
   ["hex literal"        "255"       "0xff"]
   ["hex uppercase"      "31"        "0X1F"]
   ["bigint suffix N"    "42"        "42N"]