Add testcase for #5688

tests/closure/tnested.nim

@@ -33,6 +33,7 @@ py
 py
 px
 6
+proc (){.closure, gcsafe, locks: 0.}
 '''
 """
 
@@ -177,3 +178,19 @@ block tclosure2:
 
 
     outer2()
+
+# bug #5688
+
+import typetraits
+
+proc myDiscard[T](a: T) = discard
+
+proc foo() =
+  let a = 5
+  let f = (proc() =
+             myDiscard (proc() = echo a)
+          )
+  echo name(type(f))
+
+foo()
+