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  1. Groovy
  2. GROOVY-7597

Static Compiler tries to cast delegate to target type of property accessor

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      Description

      I've been able to finally isolate a static compiler issue with accessing properties on delegates that occur within our projects:

      class Calculation {
        boolean isValid() { true }
      }
      
      class Entity {
        Calculation getCalculation(String name) { new Calculation() }
      }
      
      class Feature extends Entity {
      }
      
      void DoWithFeature(@DelegatesTo(Feature) Closure c) {
        new Feature().with(c)
      }
      
      @groovy.transform.CompileStatic
      void doIt() {
        DoWithFeature() {
          println getCalculation("whatever").valid
        }
      }
      
      doIt()
      

      The result is java.lang.ClassCastException: Feature cannot be cast to Calculation

      Workarounds:

      • change the property access into a method access "valid" -> "isValid()"
      • Remove CompileStatic annotation

      As seen in the following bytecode, the static compiler tries to cast the delegate to Calculation (which always fails), then tries to call ScriptBytecodeAdapter.castToType to try to cast the "Calculation" back to an Entity to properly call getCalculation("").isValid() on it.

        // access flags 0x1
        public doCall(Ljava/lang/Object;)Ljava/lang/Object;
         L0
          LINENUMBER 19 L0
          ALOAD 0
          CHECKCAST script1442861431462$_doIt_closure1
          INVOKEVIRTUAL script1442861431462$_doIt_closure1.getThisObject ()Ljava/lang/Object;
          LDC Lgroovy/lang/Script;.class
          INVOKESTATIC org/codehaus/groovy/runtime/ScriptBytecodeAdapter.castToType (Ljava/lang/Object;Ljava/lang/Class;)Ljava/lang/Object;
          CHECKCAST groovy/lang/Script
          ALOAD 0
          CHECKCAST script1442861431462$_doIt_closure1
          INVOKEVIRTUAL script1442861431462$_doIt_closure1.getDelegate ()Ljava/lang/Object;
          CHECKCAST Calculation
          LDC LEntity;.class
          INVOKESTATIC org/codehaus/groovy/runtime/ScriptBytecodeAdapter.castToType (Ljava/lang/Object;Ljava/lang/Class;)Ljava/lang/Object;
          CHECKCAST Entity
          LDC "whatever"
          INVOKEVIRTUAL Entity.getCalculation (Ljava/lang/String;)LCalculation;
          INVOKEVIRTUAL Calculation.isValid ()Z
          INVOKESTATIC java/lang/Boolean.valueOf (Z)Ljava/lang/Boolean;
          INVOKEVIRTUAL groovy/lang/Script.println (Ljava/lang/Object;)V
          ACONST_NULL
          ARETURN
         L1
          ACONST_NULL
          ARETURN
          LOCALVARIABLE this Lscript1442861431462$_doIt_closure1; L0 L1 0
          LOCALVARIABLE it Ljava/lang/Object; L0 L1 1
          MAXSTACK = 3
          MAXLOCALS = 2
      

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              • Assignee:
                melix Cédric Champeau
                Reporter:
                gillius Jason Winnebeck
              • Votes:
                1 Vote for this issue
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                Dates

                • Created:
                  Updated:
                  Resolved: