reverting to 26a28ab behaviour

This is only slightly problematic for the most pathological of cases
where a prelude is followed by a set of statements, none of which
generate top-level variables or attempt to return. In these cases, the
non-prelude statements will be indented. See related discussion at
e4b3e83.

src/nodes.coffee

@@ -243,12 +243,16 @@ exports.Block = class Block extends Base
   # It would be better not to generate them in the first place, but for now,
   # clean up obvious double-parentheses.
   compileRoot: (o) ->
-    o.indent  = if o.bare then '' else TAB
+    o.indent  = ""
     o.scope   = new Scope null, this, null
     o.level   = LEVEL_TOP
     @spaced   = yes
     prelude   = ""
-    unless o.bare
+    hasReturn = no
+    @traverseChildren no, (e) ->
+      hasReturn = yes if e instanceof Return
+      !hasReturn
+    if hasReturn or not o.bare
       preludeExps = for exp, i in @expressions
         e = exp.unwrap()
         break unless e instanceof Comment or e instanceof Literal
@@ -257,9 +261,13 @@ exports.Block = class Block extends Base
       @expressions = preludeExps
       prelude = "#{@compileNode o}\n" if preludeExps.length
       @expressions = rest
+      # We assume that we will need the safety wrapper.
+      # This is the best we can do without compiling twice.
+      o.indent = TAB
     code = @compileWithDeclarations o
-    return prelude + code if o.bare
-    "#{prelude}(function() {\n#{code}\n}).call(this);\n"
+    if hasReturn or (not o.bare and o.scope.variables.length > 1)
+      return "#{prelude}(function() {\n#{code}\n}).call(this);\n"
+    prelude + code
 
   # Compile the expressions body for the contents of a function, with
   # declarations of all inner variables pushed up to the top.