repro.clj

;; consumes all memory
((fn foo [s]
   ((^:once fn bar []
            (last s))))
 (range))

;; bytecode inspection summary: foo clears its local copy of s, but bar never clears its closed-over copy

;; disassembly of bar:
user> (println (disassemble-str 
                ((fn foo [s]
                   (^:once fn bar [] (last s)))
                 (range))))
// Compiled from eb4fe7045dd90b031abb30e4e26ac1dfd5eb76ac-init.clj (version 1.5 : 49.0, super bit)
public final class user$eval2344$foo__2345$bar__2346 extends clojure.lang.AFunction {
  
  // Field descriptor #7 Ljava/lang/Object;
  java.lang.Object s;
  
  // Field descriptor #18 Lclojure/lang/Var;
  public static final clojure.lang.Var const__0;
  
  // Method descriptor #9 (Ljava/lang/Object;)V
  // Stack: 2, Locals: 2
  public user$eval2344$foo__2345$bar__2346(java.lang.Object arg0);
     0  aload_0 [this]
     1  invokespecial clojure.lang.AFunction() [12]
     4  aload_0 [this]
     5  aload_1 [arg0]
     6  putfield user$eval2344$foo__2345$bar__2346.s : java.lang.Object [14]
     9  return
      Line numbers:
        [pc: 0, line: 1]
  
  // Method descriptor #16 ()Ljava/lang/Object;
  // Stack: 2, Locals: 1
  public java.lang.Object invoke();
     0  getstatic user$eval2344$foo__2345$bar__2346.const__0 : clojure.lang.Var [20]
     3  invokevirtual clojure.lang.Var.getRawRoot() : java.lang.Object [25]
     6  checkcast clojure.lang.IFn [27]
     9  aload_0 [this]
    10  getfield user$eval2344$foo__2345$bar__2346.s : java.lang.Object [14]
    13  invokeinterface clojure.lang.IFn.invoke(java.lang.Object) : java.lang.Object [30] [nargs: 2]
    18  areturn
      Line numbers:
        [pc: 0, line: 1]
        [pc: 6, line: 1]
        [pc: 13, line: 1]
      Local variable table:
        [pc: 0, pc: 18] local: this index: 0 type: java.lang.Object
  
  // Method descriptor #10 ()V
  // Stack: 2, Locals: 0
  public static {};
     0  ldc <String "clojure.core"> [34]
     2  ldc <String "last"> [36]
     4  invokestatic clojure.lang.RT.var(java.lang.String, java.lang.String) : clojure.lang.Var [42]
     7  checkcast clojure.lang.Var [22]
    10  putstatic user$eval2344$foo__2345$bar__2346.const__0 : clojure.lang.Var [20]
    13  return
      Line numbers:
        [pc: 0, line: 1]

}