Fixing #600. JS statements that must be expressions but contain pure statements cause syntax errors.

lib/nodes.js

@@ -31,13 +31,13 @@
       this.options = o ? merge(o) : {};
       this.tab = o.indent;
       top = this.topSensitive() ? this.options.top : del(this.options, 'top');
-      closure = this.isStatement(o) && !this.isPureStatement() && !top && !this.options.asStatement && !(this instanceof Comment) && !this.containsPureStatement();
+      closure = this.isStatement(o) && !this.isPureStatement() && !top && !this.options.asStatement && !(this instanceof Comment);
       code = closure ? this.compileClosure(this.options) : this.compileNode(this.options);
       return code;
     };
     Base.prototype.compileClosure = function(o) {
       o.sharedScope = o.scope;
-      return Closure.wrap(this).compile(o);
+      return Closure.wrap(this, false, true).compile(o);
     };
     Base.prototype.compileReference = function(o, options) {
       var _len, compiled, i, node, pair, reference;
@@ -484,7 +484,7 @@
       var method, name;
       method = o.scope.method;
       if (!method) {
-        throw Error("cannot call super outside of a function");
+        throw Error("cannot call super outside of a function.");
       }
       name = method.name;
       if (!name) {
@@ -1910,8 +1910,14 @@
     }
   };
   Closure = {
-    wrap: function(expressions, statement) {
+    wrap: function(expressions, statement, force) {
       var args, call, func, mentionsArgs, meth;
+      if (expressions.containsPureStatement()) {
+        if (!force) {
+          return expressions;
+        }
+        throw new Error('cannot include a pure statement in an expression.');
+      }
       if (expressions.containsPureStatement()) {
         return expressions;
       }

src/nodes.coffee

@@ -44,8 +44,7 @@ exports.Base = class Base
     @tab     = o.indent
     top     = if @topSensitive() then @options.top else del @options, 'top'
     closure = @isStatement(o) and not @isPureStatement() and not top and
-              not @options.asStatement and this not instanceof Comment and
-              not @containsPureStatement()
+              not @options.asStatement and this not instanceof Comment
     code = if closure then @compileClosure(@options) else @compileNode(@options)
     code
 
@@ -53,7 +52,7 @@ exports.Base = class Base
   # object with their parent closure, to preserve the expected lexical scope.
   compileClosure: (o) ->
     o.sharedScope = o.scope
-    Closure.wrap(this).compile o
+    Closure.wrap(this, no, yes).compile o
 
   # If the code generation wishes to use the result of a complex expression
   # in multiple places, ensure that the expression is only ever evaluated once,
@@ -447,7 +446,7 @@ exports.Call = class Call extends Base
   # Grab the reference to the superclass' implementation of the current method.
   superReference: (o) ->
     {method} = o.scope
-    throw Error "cannot call super outside of a function" unless method
+    throw Error "cannot call super outside of a function." unless method
     {name} = method
     throw Error "cannot call super on an anonymous function." unless name
     if method.klass
@@ -1617,7 +1616,10 @@ Closure =
   # Wrap the expressions body, unless it contains a pure statement,
   # in which case, no dice. If the body mentions `this` or `arguments`,
   # then make sure that the closure wrapper preserves the original values.
-  wrap: (expressions, statement) ->
+  wrap: (expressions, statement, force) ->
+    if expressions.containsPureStatement()
+      return expressions unless force
+      throw new Error 'cannot include a pure statement in an expression.'
     return expressions if expressions.containsPureStatement()
     func = new Parens new Code [], Expressions.wrap [expressions]
     args = []