closes #179; disallowed cascades without &

Author: satyr

lib/ast.js

@@ -520,6 +520,7 @@ exports.Literal = Literal = (function(superclass){
       if (!(val = o.cascadee)) {
         this.carp('stray cascadee');
       }
+      val.referred = true;
     }
     return val;
   };
@@ -3134,11 +3135,18 @@ exports.Cascade = Cascade = (function(superclass){
   }
   prototype.children = ['target', 'block'];
   prototype.terminator = '';
+  prototype.makeReturn = function(it){
+    this.block.makeReturn(it);
+    return this;
+  };
   prototype.compileNode = function(o){
     var ref, t, b;
     this.temps = [ref = o.scope.temporary('x')];
     t = ref + ' = ' + this.target.compile(o, LEVEL_LIST);
-    b = this.block.compile((o.cascadee = ref, o));
+    o.level && (o.level = LEVEL_PAREN);
+    o.cascadee = new String(ref);
+    b = this.block.compile(o);
+    o.cascadee.referred || this.carp('unreferred cascadee');
     if (o.level) {
       return "(" + t + ", " + b + ")";
     } else {

src/ast.co

@@ -323,7 +323,9 @@ class exports.Literal extends Atom
     case \debugger then if level
       return "(function(){\n#TAB#{o.indent}debugger;\n#{o.indent}}())"
     case \* then @carp 'stray star'
-    case \& then @carp 'stray cascadee' unless val = o.cascadee
+    case \&
+      @carp 'stray cascadee' unless val = o.cascadee
+      val.referred = true
     val
 
 #### Var
@@ -1911,18 +1913,23 @@ class exports.Label extends Node
       else it.compile o
 
 #### Cascade
-#
+# A construction that allows `&`-references to target expression.
 class exports.Cascade extends Node
   (@target, @block) ->
 
   children: <[ target block ]>
 
   terminator: ''
 
+  makeReturn: -> @block.makeReturn it; this
+
   compileNode: (o) ->
     @temps = [ref = o.scope.temporary \x]
     t = ref + ' = ' + @target.compile o, LEVEL_LIST
-    b = @block.compile o <<< cascadee: ref
+    o.level &&= LEVEL_PAREN
+    o.cascadee = new String ref
+    b = @block.compile o
+    o.cascadee.referred or @carp 'unreferred cascadee'
     if o.level then "(#t, #b)" else "#t;\n#b"
 
 #### JS

test/literal.co

@@ -444,3 +444,5 @@ eq
   ok &valueOf!
 
 compileThrows 'stray cascadee' 2 '\n&'
+
+compileThrows 'unreferred cascadee' 1 'a\n b'