Fix function literals as arguments

Author: a1q0

src/rewriter.coffee

@@ -77,11 +77,39 @@ exports.Rewriter = class Rewriter
   detectEnd: (i, condition, action, opts = {}) ->
     {tokens} = this
     levels = 0
+    inImplicitCall = false
     while token = tokens[i]
       return action.call this, token, i if levels is 0 and condition.call this, token, i
+      
+      if opts.inSingleLineFunctionLiteral
+        backStack = []
+        j = i
+        
+        # walk backwards til start of current expression ignoring generated tokens
+        while j >= 0 and (backStack.length or @tag(i) not in ['->', '=>'] and (@tag(i) not in EXPRESSION_START or @tokens[i].generated) and @tag(i) not in LINEBREAKS)
+
+          # set flag if inside of implicit call, aka IMPLICIT_FUNC token followed by IMPLICIT_CALL token at current expression level
+          if @tag(j) in IMPLICIT_FUNC and @tag(j + 1) in IMPLICIT_CALL and backStack.length == 0
+            inImplicitCall = true
+            break
+
+          backStack.push @tag(j) if @tag(j) in EXPRESSION_END
+          if @tag(j) in EXPRESSION_START and backStack.length
+            backStack.pop()
+
+            # don't go back further than current expression, only the return expression matters.
+            if backStack.length == 0
+              break
+          
+          j -= 1
+
       if token[0] in EXPRESSION_START
         levels += 1
-      else if token[0] in EXPRESSION_END
+      # the comma should act as EXPRESSION_END only when 
+      # - expression levels is 0, we don't want to interfer with sub-expression.
+      # - it is not inside of an implicit call `foo(() -> implicitCall 1, 2)`
+      # - it is inside of a function literal `opts.inSingleLineFunctionLiteral`
+      else if token[0] in EXPRESSION_END or (opts.inSingleLineFunctionLiteral and (not inImplicitCall) and token[0] is ',' and levels is 0)
         levels -= 1
       if levels < 0
         return if opts.returnOnNegativeLevel
@@ -728,7 +756,7 @@ exports.Rewriter = class Rewriter
         if tag is 'ELSE' and @tag(i - 1) isnt 'OUTDENT'
           i = closeElseTag tokens, i
         tokens.splice i + 1, 0, indent
-        @detectEnd i + 2, condition, action
+        @detectEnd i + 2, condition, action, inSingleLineFunctionLiteral: tag in ['->', '=>']
         tokens.splice i, 1 if tag is 'THEN'
         return 1
       return 1