Use free variables for anonymous classes (#4826)

Fixes #4822.

Author: connec

lib/coffeescript/nodes.js

@@ -1871,11 +1871,6 @@ exports.ExecutableClassBody = class ExecutableClassBody extends Base
     if argumentsNode = @body.contains isLiteralArguments
       argumentsNode.error "Class bodies shouldn't reference arguments"
 
-    @name      = @class.name ? @defaultClassVariableName
-    directives = @walkBody()
-    @setContext()
-
-    ident   = new IdentifierLiteral @name
     params  = []
     args    = [new ThisLiteral]
     wrapper = new Code params, @body
@@ -1885,6 +1880,11 @@ exports.ExecutableClassBody = class ExecutableClassBody extends Base
 
     o.classScope = wrapper.makeScope o.scope
 
+    @name      = @class.name ? o.classScope.freeVariable @defaultClassVariableName
+    ident      = new IdentifierLiteral @name
+    directives = @walkBody()
+    @setContext()
+
     if @class.hasNameClash
       parent = new IdentifierLiteral o.classScope.freeVariable 'superClass'
       wrapper.params.push new Param parent

src/nodes.coffee

@@ -1858,6 +1858,13 @@ test "#4724: backticked expression in a class body with hoisted member", ->
   eq 42, a.x
   eq 84, a.hoisted
 
+test "#4822: nested anonymous classes use non-conflicting variable names", ->
+  Class = class
+    @a: class
+      @b: 1
+
+  eq Class.a.b, 1
+
 test "#4827: executable class body wrappers have correct context", ->
   test = ->
     class @A