File isn't properly closed in scala.xml.parsing.ConstructingParser.fromFile

[biswanaths]

The bug is trivial... ConstructingParser.fromFile uses io.Source.fromFile, without bothering to close the file.

https://github.com/scala/scala/blob/master/src/library/scala/xml/parsing/ConstructingParser.scala

That in turn can cause an exception if one calls ConstructingParsers.fromFile enough times to fill up the maximum open files limit.

Example:
scala> for(i <- 1 to 100000) xml.parsing.ConstructingParser.fromFile(new java.io.File("filename"), false)
java.io.FileNotFoundException: filename (Too many open files)
at java.io.FileInputStream.open(Native Method)
at java.io.FileInputStream.<init>(FileInputStream.java:138)
at scala.io.Source$.fromFile(Source.scala:90)
at scala.io.Source$.fromFile(Source.scala:75)
at scala.xml.parsing.ConstructingParser$.fromFile(ConstructingParser.scala:19)
at $anonfun$1.apply(<console>:8)
at $anonfun$1.apply(<console>:8)
at scala.collection.immutable.Range.foreach(Range.scala:141)
at .<init>(<console>:8)
at .<clinit>(<console>)
at .<init>(<console>:7)
at .<clinit>(<console>)
at $print(<console>)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at scala.tools.nsc.interpreter.IMain$ReadEvalPrint.call(IMain.scala:734)
at scala.tools.nsc.interpreter.IMain$Request.loadAndRun(IMain.scala:983)
at scala.tools.nsc.interpreter.IMain.loadAndRunReq$1(IMain.scala:573)
at scala.tools.nsc.interpreter.IMain.interpret(IMain.scala:604)
at scala.tools.nsc.interpreter.IMain.interpret(IMain.scala:568)
at scala.tools.nsc.interpreter.ILoop.reallyInterpret$1(ILoop.scala:745)
at scala.tools.nsc.interpreter.ILoop.interpretStartingWith(ILoop.scala:790)
at scala.tools.nsc.interpreter.ILoop.command(ILoop.scala:702)
at scala.tools.nsc.interpreter.ILoop.processLine$1(ILoop.scala:566)
at scala.tools.nsc.interpreter.ILoop.innerLoop$1(ILoop.scala:573)
at scala.tools.nsc.interpreter.ILoop.loop(ILoop.scala:576)
at scala.tools.nsc.interpreter.ILoop$$anonfun$process$1.apply$mcZ$sp(ILoop.scala:867)
at scala.tools.nsc.interpreter.ILoop$$anonfun$process$1.apply(ILoop.scala:822)
at scala.tools.nsc.interpreter.ILoop$$anonfun$process$1.apply(ILoop.scala:822)
at scala.tools.nsc.util.ScalaClassLoader$.savingContextLoader(ScalaClassLoader.scala:135)
at scala.tools.nsc.interpreter.ILoop.process(ILoop.scala:822)
at scala.tools.nsc.MainGenericRunner.runTarget$1(MainGenericRunner.scala:83)
at scala.tools.nsc.MainGenericRunner.process(MainGenericRunner.scala:96)
at scala.tools.nsc.MainGenericRunner$.main(MainGenericRunner.scala:105)
at scala.tools.nsc.MainGenericRunner.main(MainGenericRunner.scala)

Imported from : SI-7282