adding existence soaks for indexed-lookup property accesses: obj?['property']

src/grammar.coffee

@@ -251,6 +251,7 @@ grammar: {
   # Indexing into an object or array.
   Index: [
     o "INDEX_START Expression INDEX_END",       -> new IndexNode($2)
+    o "SOAKED_INDEX_START Expression SOAKED_INDEX_END", -> new IndexNode($2, 'soak')
   ]
 
   # An object literal.

src/lexer.coffee

@@ -246,13 +246,21 @@ lex::literal_token: ->
   value: match and match[1]
   @tag_parameters() if value and value.match(CODE)
   value ||= @chunk.substr(0, 1)
+  not_spaced: not @prev() or not @prev().spaced
   tag: value
   if value.match(ASSIGNMENT)
     tag: 'ASSIGN'
     throw new Error('SyntaxError: Reserved word "' + @value() + '" on line ' + @line + ' can\'t be assigned') if JS_FORBIDDEN.indexOf(@value()) >= 0
-  tag: 'TERMINATOR' if value == ';'
-
-  if CALLABLE.indexOf(@tag()) >= 0 and (not @prev() or not @prev().spaced)
+  else if value is ';'
+    tag: 'TERMINATOR'
+  else if value is '[' and @tag() is '?' and not_spaced
+    tag: 'SOAKED_INDEX_START'
+    @soaked_index: true
+    @tokens.pop()
+  else if value is ']' and @soaked_index
+    tag: 'SOAKED_INDEX_END'
+    @soaked_index: false
+  else if CALLABLE.indexOf(@tag()) >= 0 and not_spaced
     tag: 'CALL_START'  if value is '('
     tag: 'INDEX_START' if value is '['
   @token tag, value

src/nodes.coffee

@@ -283,7 +283,7 @@ ValueNode: exports.ValueNode: inherit Node, {
 
     for prop in props
       @source: baseline
-      if prop instanceof AccessorNode and prop.soak
+      if prop.soak_node
         soaked: true
         if @base instanceof CallNode and prop is props[0]
           temp: o.scope.free_variable()
@@ -405,7 +405,7 @@ AccessorNode: exports.AccessorNode: inherit Node, {
   constructor: (name, tag) ->
     @children:  [@name: name]
     @prototype: tag is 'prototype'
-    @soak:      tag is 'soak'
+    @soak_node: tag is 'soak'
     this
 
   compile_node: (o) ->
@@ -417,8 +417,9 @@ AccessorNode: exports.AccessorNode: inherit Node, {
 IndexNode: exports.IndexNode: inherit Node, {
   type: 'Index'
 
-  constructor: (index) ->
-    @children: [@index: index]
+  constructor: (index, tag) ->
+    @children:  [@index: index]
+    @soak_node: tag is 'soak'
     this
 
   compile_node: (o) ->

src/rewriter.coffee

@@ -7,7 +7,8 @@ exports.Rewriter: re: ->
 
 # Tokens that must be balanced.
 BALANCED_PAIRS: [['(', ')'], ['[', ']'], ['{', '}'], ['INDENT', 'OUTDENT'],
-  ['PARAM_START', 'PARAM_END'], ['CALL_START', 'CALL_END'], ['INDEX_START', 'INDEX_END']]
+  ['PARAM_START', 'PARAM_END'], ['CALL_START', 'CALL_END'],
+  ['INDEX_START', 'INDEX_END'], ['SOAKED_INDEX_START', 'SOAKED_INDEX_END']]
 
 # Tokens that signal the start of a balanced pair.
 EXPRESSION_START: pair[0] for pair in BALANCED_PAIRS