improve errors, a bit

src/errors.janet

@@ -78,27 +78,51 @@
  (def {:line line-num :source source :input input :start start} (get-in e [:node :token]))
  (def source-line (get-line source line-num))
  (print "  on line " line-num " in " input ", ")
- (print "  binding " (b/show (e :value)))
+ (print "  matching: " (b/show (e :value)))
  (def pattern (get-in e [:node :data 0]))
- (print "  to " (b/show-patt pattern))
+ (print "  with pattern: " (b/show-patt pattern))
+ (print "  >>> " source-line)
+ (print (caret source line-num start))
+ e)
+
+(defn- match-no-match [e]
+ (print "Ludus panicked! no match")
+ (def {:line line-num :source source :input input :start start} (get-in e [:node :token]))
+ (print "  on line " line-num " in " input ", ")
+ (def value (e :value))
+ (print "  matching: " (b/show value))
+ (print "  with patterns:")
+ (def clauses (get-in e [:node :data 1]))
+ (def patterns (b/pretty-patterns {:body clauses}))
+ (def fmt-patt (do
+  (def lines (string/split "\n" patterns))
+  (def indented (map (fn [x] (string "    " x)) lines))
+  (string/join indented "\n")
+  ))
+ (print fmt-patt)
+ (def source-line (get-line source line-num))
  (print "  >>> " source-line)
  (print (caret source line-num start))
  e)
 
 (defn- generic-panic [e]
  (def msg (e :msg))
- (def {:line line-num :source source :input input} (get-in e [:node :token]))
+ (def {:line line-num :source source :input input :start start} (get-in e [:node :token]))
  (def source-line (get-line source line-num))
  (print "Ludus panicked! " msg)
  (print "  on line " line-num " in " input ":")
- (print "  >>> " source-line))
+ (print "  >>> " source-line)
+ (print (caret source line-num start))
+ e)
 
 (defn- unbound-name [e]
- (def {:line line-num :source source :lexeme name :input input} (get-in e [:node :token]))
+ (def {:line line-num :source source :lexeme name :input input :start start} (get-in e [:node :token]))
  (def source-line (get-line source line-num))
  (print "Ludus panicked! unbound name " name)
  (print "  on line " line-num " in " input ":")
- (print "  >>> " source-line))
+ (print "  >>> " source-line)
+ (print (caret source line-num start))
+ e)
 
 (defn runtime-error [e]
  (when (= :string (type e)) 
@@ -109,6 +133,8 @@
  (case msg
   "no match: function call" (fn-no-match e)
   "no match: let binding" (let-no-match e)
+  "no match: match form" (match-no-match e)
+  "no match: when form" (generic-panic e)
   "unbound name" (unbound-name e)
   (generic-panic e))
  e)

src/ludus.janet

@@ -52,7 +52,12 @@
 # (comment
 (do
 (def source `
-box foo = nil
+match :foo with {
+ :bar -> :baz
+ :baz -> :quux
+ "thing {foo}" -> "worste"
+ 42 -> 23
+}
 `)
 (def out (-> source 
  ludus