Fix 5085 (#5145) · jashkenas/coffeescript@63ffe0a

Original file line number	Diff line number	Diff line change
`@@ -1922,3 +1922,16 @@ test "#4609: Support new.target", ->`
`1922`	`1922`
`1923`	`1923`	`new Foo()`
`1924`	`1924`	`eq newTarget, yes`
	`1925`	`+`
	`1926`	`+test "#5085: Bug: @ reference to class not maintained in do block", ->`
	`1927`	`+thisFoo = 'initial foo'`
	`1928`	`+thisBar = 'initial bar'`
	`1929`	`+fn = (o) -> o.bar()`
	`1930`	`+`
	`1931`	`+class A`
	`1932`	`+@foo = 'foo assigned in class'`
	`1933`	`+do => thisFoo = @foo`
	`1934`	`+fn bar: => thisBar = @foo`
	`1935`	`+`
	`1936`	`+eq thisFoo, 'foo assigned in class'`
	`1937`	`+eq thisBar, 'foo assigned in class'`