clarified errors on implicit tokens (#214)

lib/coco.js

@@ -16,6 +16,11 @@ parser.lexer = {
     return '';
   }
 };
+parser.parseError = function(){
+  var token;
+  token = this.lexer.tokens[this.lexer.pos];
+  throw SyntaxError("unexpected " + lexer.pp(token) + " on line " + (token[2] + 1));
+};
 exports.VERSION = '0.9.2b';
 exports.compile = function(code, options){
   var e, that;

lib/lexer.js

@@ -15,6 +15,17 @@ exports.rewrite = function(it){
   }
   return it;
 };
+exports.pp = function(token){
+  var tag, val;
+  tag = token[0], val = token[1];
+  if (!val) {
+    return "`" + tag + "` (implicit)";
+  }
+  if (/^\s+/.test(val)) {
+    return tag;
+  }
+  return "`" + val + "`";
+};
 exports.tokenize = function(code, o){
   var i, c, that;
   this.inter || (code = code.replace(/[\r\u2028\u2029\uFEFF]/g, ''));
@@ -1395,12 +1406,12 @@ function expandLiterals(tokens){
       i += ts.length - 1;
       break;
     case 'WORDS':
-      ts = [['[', '[', lno = token[2]]];
+      ts = [['[', '<[', lno = token[2]]];
       for (i$ = 0, len$ = (ref4$ = token[1].slice(2, -2).match(/\S+/g) || '').length; i$ < len$; ++i$) {
         word = ref4$[i$];
-        ts.push(['STRNUM', string('\'', word, lno), lno], [',', ',', lno]);
+        ts.push(['STRNUM', string('\'', word, lno), lno], [',', '', lno]);
       }
-      tokens.splice.apply(tokens, [i, 1].concat(slice$.call(ts), [[']', ']', lno]]));
+      tokens.splice.apply(tokens, [i, 1].concat(slice$.call(ts), [[']', ']>', lno]]));
       i += ts.length;
       break;
     case 'INDENT':
@@ -1437,11 +1448,11 @@ function expandLiterals(tokens){
       continue;
     }
     if (token.spaced && of$(tokens[i + 1][0], ARG)) {
-      tokens.splice(++i, 0, [',', ',', token[2]]);
+      tokens.splice(++i, 0, [',', '', token[2]]);
     }
   }
   function fn$(){
-    if (0x10000 < ts.push(['STRNUM', enc(n), lno], [',', ',', lno])) {
+    if (0x10000 < ts.push(['STRNUM', enc(n), lno], [',', '', lno])) {
       carp('range limit exceeded', lno);
     }
   }

src/coco.co

@@ -8,12 +8,17 @@ lexer = require \./lexer
 # the generic stream of tokens our lexer produces.
 {parser} = require \./parser
 parser import
-  yy    : require \./ast
-  lexer :
+  yy: require \./ast
+
+  lexer:
     lex           : -> [tag, @yytext, @yylineno] = @tokens[++@pos] or ['']; tag
     setInput      : -> @pos = -1; @tokens = it
     upcomingInput : -> ''
 
+  parseError: ->
+    token = @lexer.tokens[@lexer.pos]
+    throw SyntaxError "unexpected #{lexer.pp token} on line #{token.2 + 1}"
+
 exports import
   VERSION: \0.9.2b
 

src/lexer.co

@@ -35,6 +35,12 @@ exports import
     it.shift! if it.0?0 is \NEWLINE
     it
 
+  # Pretty-prints a token for errors.
+  pp: ([tag, val]:token) ->
+    return "`#tag` (implicit)" unless val
+    return tag if /^\s+/test val
+    "`#val`"
+
   #### Main Loop
 
   tokenize: (code, o) ->
@@ -947,7 +953,7 @@ character = if JSON!? then uxxxx else ->
       ts  = []
       enc = if char then character else String
       add = !->
-         if 0x10000 < ts.push [\STRNUM enc n; lno] [\, \, lno]
+         if 0x10000 < ts.push [\STRNUM enc n; lno] [\, '' lno]
            carp 'range limit exceeded' lno
       if token.op is \to
       then add! for n from from to  to by by
@@ -956,10 +962,10 @@ character = if JSON!? then uxxxx else ->
       tokens.splice i, 2 + 2 * byp, ...ts
       i += ts.length - 1
     case \WORDS
-      ts = [[\[ \[ lno = token.2]]
+      ts = [[\[ \<[ lno = token.2]]
       for word of token.1.slice 2 -2 .match /\S+/g or ''
-        ts.push [\STRNUM; string \', word, lno; lno] [\, \, lno]
-      tokens.splice i, 1, ...ts, [\] \] lno]
+        ts.push [\STRNUM; string \', word, lno; lno] [\, '' lno]
+      tokens.splice i, 1, ...ts, [\] \]> lno]
       i += ts.length
     case \INDENT
       if tokens[i-1]
@@ -976,7 +982,7 @@ character = if JSON!? then uxxxx else ->
     case \CREMENT  then continue unless able tokens, i
     default continue
     if token.spaced and tokens[i+1]0 of ARG
-      tokens.splice ++i, 0 [\, \, token.2]
+      tokens.splice ++i, 0 [\, '' token.2]
 
 # Seeks `tokens` from `i`ndex and `go` for a token of the same level
 # that's `ok` or an unmatched closer.

test/compilation.co

@@ -136,7 +136,7 @@ eq '''
 ''', Coco.compile '''try for k in o then let then ^@'''
 
 
-eq 'STRNUM,0,0 ,,,,0 STRNUM,1,1' Coco.tokens('''
+eq 'STRNUM,0,0 ,,,0 STRNUM,1,1' Coco.tokens('''
 0 \\
   1
 ''').slice(0 3).join ' '

test/if.co

@@ -101,7 +101,7 @@ ok if true then -> 1
 
 
 # [coffee#1026](https://github.com/jashkenas/coffee-script/issues/1026)
-throws "Parse error on line 2: Unexpected 'ELSE'", -> Coco.ast '''
+throws "unexpected `else` on line 3", -> Coco.ast '''
   if a then b
   else then c
   else then d

test/literal.co

@@ -394,6 +394,8 @@ eq o.1, \1
 eq o.3, 3
 eq o.5, 5
 
+compileThrows 'unexpected `,` (implicit)' 1 '0 1'
+
 
 ### Numeric/Character Ranges
 show = -> @@ * ' '

test/string.co

@@ -203,7 +203,7 @@ eq 'multiline nested "interpolations" work', """multiline #{
 
 compileThrows 'unterminated interpolation' 2 '"#{\n'
 
-throws "Parse error on line 1: Unexpected ')'" -> Coco.compile '"(#{+})"'
+compileThrows "unexpected `)`" 1 '"(#{+})"'
 
 compileThrows 'invalid variable interpolation "if"' 1 '"#if"'