Fixing issue #1046.

lib/lexer.js

@@ -480,7 +480,7 @@
       throw new Error("missing " + (stack.pop()) + ", starting on line " + (this.line + 1));
     };
     Lexer.prototype.interpolateString = function(str, options) {
-      var expr, heredoc, i, inner, interpolated, letter, nested, pi, regex, tag, tokens, value, _len, _ref, _ref2, _ref3;
+      var expr, heredoc, i, inner, interpolated, len, letter, nested, pi, regex, tag, tokens, value, _len, _ref, _ref2, _ref3;
       if (options == null) {
         options = {};
       }
@@ -509,11 +509,13 @@
           if (((_ref = nested[0]) != null ? _ref[0] : void 0) === 'TERMINATOR') {
             nested.shift();
           }
-          if (nested.length > 1) {
-            nested.unshift(['(', '(']);
-            nested.push([')', ')']);
+          if (len = nested.length) {
+            if (len > 1) {
+              nested.unshift(['(', '(']);
+              nested.push([')', ')']);
+            }
+            tokens.push(['TOKENS', nested]);
           }
-          tokens.push(['TOKENS', nested]);
         }
         i += expr.length;
         pi = i + 1;

src/lexer.coffee

@@ -439,10 +439,11 @@ exports.Lexer = class Lexer
         nested = new Lexer().tokenize inner, line: @line, rewrite: off
         nested.pop()
         nested.shift() if nested[0]?[0] is 'TERMINATOR'
-        if nested.length > 1
-          nested.unshift ['(', '(']
-          nested.push    [')', ')']
-        tokens.push ['TOKENS', nested]
+        if len = nested.length
+          if len > 1
+            nested.unshift ['(', '(']
+            nested.push    [')', ')']
+          tokens.push ['TOKENS', nested]
       i += expr.length
       pi = i + 1
     tokens.push ['NEOSTRING', str.slice pi] if i > pi < str.length

test/string_literals.coffee

@@ -101,3 +101,7 @@ eq ''' '\\\' ''', " '\\' "
 eq """ "\\\" """, ' "\\" '
 
 eq '''  <- keep these spaces ->  ''', '  <- keep these spaces ->  '
+
+
+test "#1046, empty string interpolations", ->
+  eq "#{ }", ''