Aladdin - Scala Bugtracking

	[#1033]	project: compiler	priority: low	category: bug
	submitter	assigned to	status	date submitted
	Sean	Burak	fixed	2007-03-31 13:03:45.0
subject	pattern matching backend crash
code	package test; object Crash { case class Token(val text : String); class KeywordToken(override val text : String) extends Token(text); def factoryFor(tok : Token) = tok match { case Token("hello") => "world"; case t : KeywordToken => t.text; } }
what happened	sean-mcdirmid:~/workspace/test11/src mcdirmid$ ../../scala/build/ quick/bin/scalac -d ../bin/ test/Crash.scala Exception in thread "main" def factoryFor(tok: test.Crash$Token (REFERENCE(test.Crash$Token))): java.lang.String { locals: value tok, value temp3, value temp4, variable eqEqTemp$, value temp5, value temp6, value t startBlock: 1 blocks: [1,2,3,4,5,6,8,9,10,11,14] 1: SCOPE_ENTER value temp3 LOAD_LOCAL value tok STORE_LOCAL value temp3 LOAD_LOCAL value temp3 CZJUMP (REFERENCE(java.lang.Object))EQ ? 3 : 2 2: SCOPE_ENTER value temp3 LOAD_LOCAL value temp3 STORE_LOCAL value temp3 SCOPE_ENTER value temp4 LOAD_LOCAL value temp3 CALL_METHOD test.Crash$Tokentest.Crash$Token.text (dynamic) STORE_LOCAL value temp4 LOAD_LOCAL value temp4 CONSTANT (Constant(hello)) STORE_LOCAL variable eqEqTemp$ DUP CZJUMP (REFERENCE(java.lang.Object))EQ ? 8 : 9 3: NEW REFERENCE(scala.MatchError) DUP LOAD_LOCAL value temp3 CALL_METHOD scala.MatchErrorscala.MatchError. (static-instance) THROW 4: RETURN (REFERENCE(java.lang.String)) 5: SCOPE_ENTER value temp5 CONSTANT (Constant(hello)) STORE_LOCAL value temp5 CONSTANT (Constant(world)) DROP REFERENCE(java.lang.String) CONSTANT (Constant(world)) SCOPE_EXIT value temp5 JUMP 4 6: LOAD_LOCAL value temp3 IS_INSTANCE REFERENCE(test.Crash$KeywordToken) CZJUMP (BOOL)NE ? 10 : 11 8: DROP REFERENCE(java.lang.Object) LOAD_LOCAL variable eqEqTemp$ CZJUMP (REFERENCE(java.lang.Object))EQ ? 5 : 6 9: LOAD_LOCAL variable eqEqTemp$ CALL_METHOD java.lang.Objectjava.lang.Object.equals (dynamic) CZJUMP (BOOL)NE ? 5 : 6 10: SCOPE_ENTER value temp6 LOAD_LOCAL value temp3 CHECK_CAST REFERENCE(test.Crash$KeywordToken) STORE_LOCAL value temp6 SCOPE_ENTER value t LOAD_LOCAL value temp3 CHECK_CAST REFERENCE(test.Crash$KeywordToken) STORE_LOCAL value t SCOPE_ENTER value t LOAD_LOCAL value temp6 STORE_LOCAL value t LOAD_LOCAL value t LOAD_LOCAL value t STORE_LOCAL value t STORE_LOCAL value t JUMP 14 11: NEW REFERENCE(scala.MatchError) DUP LOAD_LOCAL value temp3 CALL_METHOD scala.MatchErrorscala.MatchError. (static-instance) THROW 14: LOAD_LOCAL value t CALL_METHOD test.Crash$KeywordTokentest.Crash$KeywordToken.text (dynamic) SCOPE_EXIT value t SCOPE_EXIT value t SCOPE_EXIT value temp6 JUMP 4 } Exception handlers: Illegal local var nesting: test.Crash.factoryFor Current method: test.Crash.factoryFor Current block: 14 Current instruction: SCOPE_EXIT value t ---------------------() at scala.tools.nsc.backend.jvm.GenJVM$BytecodeGenerator$$anonfun $41.assert$0(GenJVM.scala:661) at scala.tools.nsc.backend.jvm.GenJVM$BytecodeGenerator$$anonfun $41.apply(GenJVM.scala:995) at scala.tools.nsc.backend.jvm.GenJVM$BytecodeGenerator$$anonfun $41.apply(GenJVM.scala:650) at scala.Iterator$class.foreach(Iterator.scala:380) at scala.runtime.BoxedArray$$anon$0.foreach(BoxedArray.scala:46) at scala.Iterable$class.foreach(Iterable.scala:197) at scala.runtime.BoxedArray.foreach(BoxedArray.scala:25) at scala.tools.nsc.backend.icode.BasicBlocks$BasicBlock.traverse (BasicBlocks.scala:102) at scala.tools.nsc.backend.jvm.GenJVM$BytecodeGenerator.genBlock (GenJVM.scala:650) at scala.tools.nsc.backend.jvm.GenJVM$BytecodeGenerator.genBlocks (GenJVM.scala:571) at scala.tools.nsc.backend.jvm.GenJVM$BytecodeGenerator.genBlocks (GenJVM.scala:571) at scala.tools.nsc.backend.jvm.GenJVM$BytecodeGenerator.genBlocks (GenJVM.scala:571) at scala.tools.nsc.backend.jvm.GenJVM$BytecodeGenerator.genBlocks (GenJVM.scala:571) at scala.tools.nsc.backend.jvm.GenJVM$BytecodeGenerator.genBlocks (GenJVM.scala:571) at scala.tools.nsc.backend.jvm.GenJVM$BytecodeGenerator.genBlocks (GenJVM.scala:571) at scala.tools.nsc.backend.jvm.GenJVM$BytecodeGenerator.genBlocks (GenJVM.scala:571) at scala.tools.nsc.backend.jvm.GenJVM$BytecodeGenerator.genBlocks (GenJVM.scala:571) at scala.tools.nsc.backend.jvm.GenJVM$BytecodeGenerator.genCode (GenJVM.scala:560) at scala.tools.nsc.backend.jvm.GenJVM$BytecodeGenerator.genMethod (GenJVM.scala:445) at scala.tools.nsc.backend.jvm.GenJVM$BytecodeGenerator$$anonfun $6.apply(GenJVM.scala:195) at scala.tools.nsc.backend.jvm.GenJVM$BytecodeGenerator$$anonfun $6.apply(GenJVM.scala:195) at scala.List.foreach(List.scala:699) at scala.tools.nsc.backend.jvm.GenJVM$BytecodeGenerator.genClass (GenJVM.scala:195) at scala.tools.nsc.backend.jvm.GenJVM$JvmPhase$$anonfun$0.apply (GenJVM.scala:44) at scala.tools.nsc.backend.jvm.GenJVM$JvmPhase$$anonfun$0.apply (GenJVM.scala:44) at scala.Iterator$class.foreach(Iterator.scala:380) at scala.collection.Map$$anon$2.foreach(Map.scala:119) at scala.tools.nsc.backend.jvm.GenJVM$JvmPhase.run(GenJVM.scala:44) at scala.tools.nsc.Global$Run.compileSources(Global.scala:491) at scala.tools.nsc.Global$Run.compile(Global.scala:565) at scala.tools.nsc.Main$.process(Main.scala:57) at scala.tools.nsc.Main$.main(Main.scala:79) at scala.tools.nsc.Main.main(Main.scala)
what expected
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Changes of this bug report

Burak edited on 2007-04-01 15:11:23.0

There is a trouble with the pattern-matcher output (which I will take care of soon), since it generates the wrong symbol. Still, Iulian you might want to make the backend more robust against such mistakes.

  var temp3#3909: Crash#11.this.Token#3651 = tok#3866;
      if (temp3#3909.ne#2565(null))
        {
           var temp3#3909: Crash#11.this.Token#3651 = temp3#3909.asInstanceOf#2543[Crash#11.this.Token#3651]();
           var temp4#3910: java.lang.String#790 = temp3#3909.text#3772();
          if (temp4#3910.==#2549("hello"))
            {
               var temp5#3911: java.lang.String#790("hello") = "hello";
              {
                "world";
                "world"
              }
            }
          else
            if (temp3#3909.isInstanceOf#2541[Crash#11.this.KeywordToken#3652]())
              {
                 var temp6#3915: Crash#11.this.KeywordToken#3652 = temp3#3909.asInstanceOf#2543[Crash#11.this.KeywordToken#3652]();
                {
                  val t#3868: Crash#11.this.KeywordToken#3652 = temp3#3909.asInstanceOf#2543[Crash#11.this.KeywordToken#3652]();
                  val t#3868: Crash#11.this.KeywordToken#3652 = temp6#3915;
                  body10533743#3916(t#3868, t#3868);
                  body10533743#3916(t#3868,t#3868){
                    t#3868.text#3861()
                  }
                }
              }
            else
              throw new scala.MatchError#357(temp3#3909)
        }
      else
        throw new scala.MatchError#357(temp3#3909)

Iulian edited on 2007-04-02 10:44:04.0

Indeed, the backend could continue, since this is definitly something we can recover from (maybe local variable scope is not as exact as it should be). However, this most likely denotes a bug in the compiler, and silently continuing will make it easy to forget, and come back to bite us later. What should I do? A warning doesn't seem fit (it's a compiler bug, not a user mistake) and crashing only when -debug is set seems useless, since we never run with -debug unless we know already there's something fishy.

Burak edited on 2007-04-02 13:25:28.0

In fact, I thought more along the lines of crashing with a better error message... If it can be done with little effort, a good error msg would be very useful to better locate our errors (and since nobody is pursueing the ideal solution of writing and maintaining a tree checker, one will always have backend crashes of this sort due to illegal symbol uses etc). just a suggestion...

Iulian edited on 2007-05-01 09:56:40.0

I reassigned this to Burak since it's a pattern matcher bug.

Burak edited on 2007-07-06 15:15:03.0

fixed (at least when new algo is used... it's another timebomb :/ old algo should eventually be phased out)