Fix 5085 (#5145)

* Add test for #5085

    $ cake test
    failed 1 and passed 1274 tests in 4.81 seconds

      #5085: Bug: @ reference to class not maintained in do block
      AssertionError [ERR_ASSERTION]: Expected undefined to equal 2

* Fix #5085: @ reference to class in "do" block

Assuming that a bound Code node inside an ExecutableClassBody without a
name must be a "do" block.

* Additional tests

#5145 (comment)

Also switched to concat'g strings for test values, as opposed to
incrementing numbers: makes the tests a bit easier to read.

Author: brewingcode

lib/coffeescript/nodes.js

@@ -1989,7 +1989,7 @@ exports.ExecutableClassBody = class ExecutableClassBody extends Base
     @body.traverseChildren false, (node) =>
       if node instanceof ThisLiteral
         node.value   = @name
-      else if node instanceof Code and node.bound and node.isStatic
+      else if node instanceof Code and node.bound and (node.isStatic or not node.name)
         node.context = @name
 
   # Make class/prototype assignments for invalid ES properties

src/nodes.coffee

@@ -1922,3 +1922,16 @@ test "#4609: Support new.target", ->
 
   new Foo()
   eq newTarget, yes
+
+test "#5085: Bug: @ reference to class not maintained in do block", ->
+  thisFoo = 'initial foo'
+  thisBar = 'initial bar'
+  fn = (o) -> o.bar()
+
+  class A
+    @foo = 'foo assigned in class'
+    do => thisFoo = @foo
+    fn bar: => thisBar = @foo
+
+  eq thisFoo, 'foo assigned in class'
+  eq thisBar, 'foo assigned in class'