anchor.diff:      for (LocalElement loopVariable in loopVariables) {
         if (isInMutableVariable(loopVariable)) {
           ir.MutableVariable mutableVariable = getMutableVariable(loopVariable);
  -        ir.Primitive get = new ir.GetMutableVariable(mutableVariable);
  -        add(new ir.LetPrim(get));
  -        environment.update(loopVariable, get);
  +        ir.Primitive value =
  +            addPrimitive(new ir.GetMutableVariable(mutableVariable));
  +        environment.update(loopVariable, value);
           dartState.registerizedMutableVariables.add(loopVariable);
         }
       }
  
positive.code:           build(key.current), build(value.current)));
      }
      assert(!key.moveNext() && !value.moveNext());
      ir.Primitive result = new ir.LiteralMap(type, entries);
      add(new ir.LetPrim(result));
      return result;
    }
  
    /// Creates a conditional expression with the provided [condition] where the
  
negative.code:     if (env == null) return;
  
      // Obtain a reference to the function object (this).
      ir.Primitive thisPrim = addPrimitive(new ir.This());
  
      // Obtain access to the free variables.
      env.freeVariables.forEach((Local local, ClosureLocation location) {
  