Description
reproduction steps
This is using Scala 2.13.2 (Scala 2.13.{0, 1} had a bug preventing Spark from compiling) and a fork of Spark to get it to compile with 2.13 (see SPARK-25075):
git clone https://github.com/smarter/spark/ -b scala-2.13-miscompile
cd spark
sbt core/compileproblem
The class HighlyCompresse
7D7F
dMapStatus has a field numNonEmptyBlocks: https://github.com/smarter/spark/blob/ecfee82fda5f0403024ff64f16bc767b8d1e3e3d/core/src/main/scala/org/apache/spark/scheduler/MapStatus.scala#L165
This field is only used in the constructor of the class: https://github.com/smarter/spark/blob/ecfee82fda5f0403024ff64f16bc767b8d1e3e3d/core/src/main/scala/org/apache/spark/scheduler/MapStatus.scala#L174
... but scalac doesn't emit any field for it, even though it emits a getfield call for its usage in the constructor:
$ javap -p -v core/target/scala-2.13/classes/org/apache/spark/scheduler/HighlyCompressedMapStatus.class|grep numNonEmptyBlocks
#304 = Utf8 numNonEmptyBlocks
#306 = NameAndType #304:#118 // numNonEmptyBlocks:I
#307 = Fieldref #2.#306 // org/apache/spark/scheduler/HighlyCompressedMapStatus.numNonEmptyBlocks:I
65: getfield #307 // Field numNonEmptyBlocks:I
0 95 2 numNonEmptyBlocks I
numNonEmptyBlocks finalIf I add a private def foo: Int = numNonEmptyBlocks to the class, then the field does show up:
$ javap -p -v core/target/scala-2.13/classes/org/apache/spark/scheduler/HighlyCompressedMapStatus.class|grep numNonEmptyBlocks
#20 = Utf8 numNonEmptyBlocks
#50 = NameAndType #20:#21 // numNonEmptyBlocks:I
#51 = Fieldref #2.#50 // org/apache/spark/scheduler/HighlyCompressedMapStatus.numNonEmptyBlocks:I
private int numNonEmptyBlocks;
1: getfield #51 // Field numNonEmptyBlocks:I
7: putfield #51 // Field numNonEmptyBlocks:I
70: getfield #51 // Field numNonEmptyBlocks:I
0 100 2 numNonEmptyBlocks I
numNonEmptyBlocks final