Fix multi-line if-else in single-line expression.

* When searching for the closing token of a single-line expression, ignore TERMINATORS that will subsequently be removed.
* Add a test.

lib/coffee-script/rewriter.js

@@ -358,8 +358,8 @@
       var action, condition, indent, outdent, starter;
       starter = indent = outdent = null;
       condition = function(token, i) {
-        var _ref, _ref1;
-        return token[1] !== ';' && (_ref = token[0], __indexOf.call(SINGLE_CLOSERS, _ref) >= 0) && !(token[0] === 'ELSE' && starter !== 'THEN') && !(((_ref1 = token[0]) === 'CATCH' || _ref1 === 'FINALLY') && (starter === '->' || starter === '=>'));
+        var _ref, _ref1, _ref2;
+        return token[1] !== ';' && (_ref = token[0], __indexOf.call(SINGLE_CLOSERS, _ref) >= 0) && !(token[0] === 'TERMINATOR' && ((_ref1 = this.tag(i + 1)) === 'THEN' || _ref1 === 'ELSE')) && !(token[0] === 'ELSE' && starter !== 'THEN') && !(((_ref2 = token[0]) === 'CATCH' || _ref2 === 'FINALLY') && (starter === '->' || starter === '=>'));
       };
       action = function(token, i) {
         return this.tokens.splice((this.tag(i - 1) === ',' ? i - 1 : i), 0, outdent);

src/rewriter.coffee

@@ -361,6 +361,7 @@ class exports.Rewriter
 
     condition = (token, i) ->
       token[1] isnt ';' and token[0] in SINGLE_CLOSERS and
+      not (token[0] is 'TERMINATOR' and @tag(i + 1) in ['THEN', 'ELSE']) and
       not (token[0] is 'ELSE' and starter isnt 'THEN') and
       not (token[0] in ['CATCH', 'FINALLY'] and starter in ['->', '=>'])
 

test/formatting.coffee

@@ -151,3 +151,12 @@ test "#2981: Enforce initial indentation", ->
     ok no
   catch e
     eq 'missing indentation', e.message
+
+test "'single-line' expression containing multiple lines", ->
+  doesNotThrow -> CoffeeScript.compile """
+    (a, b) -> if a
+      -a
+    else if b
+    then -b
+    else null
+  """