[GROOVY-7597] Static Compiler tries to cast delegate to target type of property accessor

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.4.3, 2.4.4
• Fix Version/s: 2.4.6
• Component/s: Static compilation, Static Type Checker
• Assignee: Cédric Champeau
• Reporter: Jason Winnebeck
• Created: 21/Sep/15 18:54
• Updated: 22/Feb/16 20:48
• Resolved: 07/Oct/15 19:23

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

Issue Links

• is duplicated by: GROOVY-7376 ClassCastException when searching for a property inside a with closure