Fix #6403: Do not intercept crashes

Emitting an error when the backend crashes hides the crash from the reporter and fails which cannot be identified by the testing framework.

Author: nicolasstucki

compiler/src/dotty/tools/backend/jvm/GenBCode.scala

@@ -180,8 +180,7 @@ class GenBCodePipeline(val entryPoints: List[Symbol], val int: DottyBackendInter
             try   { /*withCurrentUnit(item.cunit)*/(visit(item)) }
             catch {
               case ex: Throwable =>
-                ex.printStackTrace()
-                ctx.error(s"Error while emitting ${int.sourceFileFor(item.cunit)}\n${ex.getMessage}")
+                throw new Exception(s"Error while emitting ${int.sourceFileFor(item.cunit)}", ex)
             }
           }
         }

compiler/test/dotty/tools/vulpix/ParallelTesting.scala

@@ -852,21 +852,21 @@ trait ParallelTesting extends RunnerOrchestration { self =>
     extends Test(testSources, times, threadLimit, suppressAllOutput) {
     protected def encapsulatedCompilation(testSource: TestSource) = new LoggedRunnable {
       def checkTestSource(): Unit = tryCompile(testSource) {
-        def fail(msg: String): Nothing = {
+        def fail(msg: String): Unit = {
           echo(msg)
           failTestSource(testSource)
-          ???
         }
         testSource match {
           case testSource@JointCompilationSource(_, files, flags, outDir, fromTasty, decompilation) =>
             val sourceFiles = testSource.sourceFiles
-            val reporter =
-              try compile(sourceFiles, flags, true, outDir)
-              catch {
-                case ex: Throwable => fail(s"Fatal compiler crash when compiling: ${testSource.title}")
-              }
-            if (reporter.compilerCrashed)
-              fail(s"Compiler crashed when compiling: ${testSource.title}")
+            try {
+              val reporter = compile(sourceFiles, flags, true, outDir)
+              if (reporter.compilerCrashed)
+                fail(s"Compiler crashed when compiling: ${testSource.title}")
+            }
+            catch {
+              case ex: Throwable => fail(s"Fatal compiler crash when compiling: ${testSource.title}")
+            }
           case testSource@SeparateCompilationSource(_, dir, flags, outDir) => unsupported("NoCrashTest - SeparateCompilationSource")
         }
         registerCompletion()