Issue #905. Fixing soaked-value-as-a-comprehension-subject ... incorrect LEVEL_TOP.

lib/nodes.js

@@ -1800,7 +1800,7 @@
           step: this.step
         }));
       } else {
-        svar = this.source.compile(o, LEVEL_TOP);
+        svar = this.source.compile(o, LEVEL_PAREN);
         if ((name || this.own) && !IDENTIFIER.test(svar)) {
           defPart = "" + this.tab + (ref = scope.freeVariable('ref')) + " = " + svar + ";\n";
           svar = ref;

src/nodes.coffee

@@ -1438,7 +1438,7 @@ exports.For = class For extends Base
     if @range
       forPart = source.compile merge(o, {index: ivar, @step})
     else
-      svar = @source.compile o, LEVEL_TOP
+      svar = @source.compile o, LEVEL_PAREN
       if (name or @own) and not IDENTIFIER.test svar
         defPart = "#{@tab}#{ref = scope.freeVariable 'ref'} = #{svar};\n"
         svar = ref

test/test_comprehensions.coffee

@@ -241,3 +241,11 @@ list = ['one', 'two']
 
 eq typeof entity, 'undefined'
 eq facets['two'](), 'two'
+
+
+# Issue #905. Soaks as the for loop subject.
+a = {b: {c: [1, 2, 3]}}
+for d in a.b?.c
+  e = d
+
+eq e, 3