Missed explicit cast for generic return type

[dsyzhu]

FAILED: testGenericResult
java.lang.VerifyError: Bad type on operand stack
Exception Details:
Location:
com/yahoo/yqlplus/generated/gen1/invocable_unit11.invoke(Lcom/yahoo/yqlplus/generated/gen1/obj_unit2;Lcom/yahoo/yqlplus/engine/TaskContext;Lcom/yahoo/yqlplus/engine/sources/SampleResultSource$Result;)Lcom/yahoo/yqlplus/generated/gen1/struct_unit12; @21: getfield
Reason:
Type 'java/lang/Object' (current frame, stack[0]) is not assignable to 'com/yahoo/yqlplus/engine/sources/SampleResultSource$Sample'
Current Frame:
bci: @21
flags: { }
locals: { 'com/yahoo/yqlplus/generated/gen1/obj_unit2', 'com/yahoo/yqlplus/engine/TaskContext', 'com/yahoo/yqlplus/engine/sources/SampleResultSource$Result', 'com/yahoo/yqlplus/generated/gen1/struct_unit12', top, 'java/lang/Object' }
stack: { 'java/lang/Object' }
Bytecode:
0x0000000: bb00 0e59 b700 0f4e 2cb6 0015 3a05 1905
0x0000010: c600 0b19 05b4 001b a700 0401 3a04 1904
0x0000020: c600 092d 1904 b500 1e2d b0
Stackmap Table:
append_frame(@27,Object[#14],Top,Object[#4])
same_locals_1_stack_item_frame(@28,Object[#35])
full_frame(@41,{Object[#37],Object[#39],Object[#17],Object[#14],Object[#35],Object[#4]},{})

at java.lang.Class.getDeclaredFields0(Native Method)
at java.lang.Class.privateGetDeclaredFields(Class.java:2583)
at java.lang.Class.getField0(Class.java:2975)
at java.lang.Class.getField(Class.java:1701)
at com.yahoo.yqlplus.engine.internal.bytecode.UnitGenerator.prepare(UnitGenerator.java:314)
at com.yahoo.yqlplus.engine.internal.bytecode.ASMClassSource.build(ASMClassSource.java:191)
at com.yahoo.yqlplus.engine.internal.compiler.ProgramEnvironment.compile(ProgramEnvironment.java:67)