Reduce boilerplate in compiler JUnit tests (#5158)

Many JUnit tests share a compiler instance between all
test cases in a class to reduce overhead.

This commit refactors the mechanism to reduce the boilerplate.

In the new scheme:

  - Using the `@ClassRule` hook in JUnit, we create a per-class
    map for each test class.
  - Per-class values are registered from the test class itself
    by calling `cached("someKey", () => mkExpensiveThing)`
  - At the end of the test, the entries in this map are `close()`-ed
    (if they implement `Closable`), and are released for
    garbage collection.)

1 files changed, 1 insertions, 7 deletions

diff --git a/test/junit/scala/tools/nsc/backend/jvm/opt/AnalyzerTest.scala b/test/junit/scala/tools/nsc/backend/jvm/opt/AnalyzerTest.scala
index 930f7f2f10..09675870f0 100644
--- a/test/junit/scala/tools/nsc/backend/jvm/opt/AnalyzerTest.scala
+++ b/test/junit/scala/tools/nsc/backend/jvm/opt/AnalyzerTest.scala
@@ -21,15 +21,9 @@ import BytecodeUtils._
 import scala.collection.JavaConverters._
 import scala.tools.testing.ClearAfterClass
 
-object AnalyzerTest extends ClearAfterClass.Clearable {
-  var noOptCompiler = newCompiler(extraArgs = "-Yopt:l:none")
-  def clear(): Unit = { noOptCompiler = null }
-}
-
 @RunWith(classOf[JUnit4])
 class AnalyzerTest extends ClearAfterClass {
-  ClearAfterClass.stateToClear = AnalyzerTest
-  val noOptCompiler = AnalyzerTest.noOptCompiler
+  val noOptCompiler = cached("compiler", () => newCompiler(extraArgs = "-Yopt:l:none"))
 
   @Test
   def aliasingOfPrimitives(): Unit = {