Better handling of ctrl-c while the compiler is running

Previously, the compiler tried its best to continue working after
ctrl-c, which usually resulted a flood of error messages. This commit
takes inspiration from scala/scala#6479 to
handle ClosedByInterruptException and InterruptedException gracefully
and avoid this.

Note that the Scala 2 PR goes further: it checks `Thread.interrupted()`
to set a global `cancelled` flag (Should we do the same with our
`Run#isCancelled` ?) and it also catches InterruptedException at the
top-level so that ctrl-c does not end up printing a stacktrace, but this
is beyond what I have the time to look at currently.

Author: smarter

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

@@ -3,6 +3,8 @@ package backend
 package jvm
 
 import java.io.{ DataOutputStream, FileOutputStream, IOException, OutputStream, File => JFile }
+import java.nio.channels.ClosedByInterruptException
+import java.nio.file.Files
 import dotty.tools.io._
 import dotty.tools.dotc.report
 
@@ -112,6 +114,15 @@ trait BytecodeWriters {
       val outstream = new DataOutputStream(outfile.bufferedOutput)
 
       try outstream.write(jclassBytes, 0, jclassBytes.length)
+      catch {
+        case ex: ClosedByInterruptException =>
+          try {
+            outfile.delete() // don't leave a empty of half-written classfile around after an interrupt
+          } catch {
+            case _: Throwable =>
+          }
+          throw ex
+      }
       finally outstream.close()
       report.informProgress("wrote '" + label + "' to " + outfile)
     }

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

@@ -190,6 +190,8 @@ class GenBCodePipeline(val int: DottyBackendInterface)(using Context) extends BC
         else {
           try   { /*withCurrentUnit(item.cunit)*/(visit(item)) }
           catch {
+            case ex: InterruptedException =>
+              throw ex
             case ex: Throwable =>
               println(s"Error while emitting ${item.cunit.source.file.name}")
               throw ex
@@ -424,6 +426,8 @@ class GenBCodePipeline(val int: DottyBackendInterface)(using Context) extends BC
               addLambdaDeserialize(plainNode, serializableLambdas)
             addToQ3(item)
           } catch {
+            case ex: InterruptedException =>
+              throw ex
             case ex: Throwable =>
               println(s"Error while emitting ${item.plain.classNode.name}")
               throw ex

compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala

@@ -3,6 +3,7 @@ package dotc
 package core
 
 import java.io.{IOException, File}
+import java.nio.channels.ClosedByInterruptException
 import scala.compat.Platform.currentTime
 import dotty.tools.io.{ ClassPath, ClassRepresentation, AbstractFile }
 import config.Config
@@ -343,6 +344,10 @@ abstract class SymbolLoader extends LazyType { self =>
       report.informTime("loaded " + description, start)
     }
     catch {
+      case ex: InterruptedException =>
+        throw ex
+      case ex: ClosedByInterruptException =>
+        throw new InterruptedException
       case ex: IOException =>
         signalError(ex)
       case NonFatal(ex: TypeError) =>