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Type system breach in multiple assignment #5106

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scabug opened this Issue Oct 22, 2011 · 3 comments

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scabug commented Oct 22, 2011

I think this deserves more than an "unchecked" warning:

scala> def f {
     | val (n, l): (String, Int) = (4, "");
     | }
warning: there were 2 unchecked warnings; re-run with -unchecked for details
f: Unit

scala> f
java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String
[...]

This is specially surprising because this other very similar case (created from #140, which I initially thought was the same bug) works as I expected:

scala> def g {
     | val (n: String, l: Int) = (4, "");
     | }
<console>:8: error: scrutinee is incompatible with pattern type;
 found   : String
 required: Int
       val (n: String, l: Int) = (4, "");
               ^
<console>:8: error: type mismatch;
 found   : String
 required: Int
       val (n: String, l: Int) = (4, "");
             ^
<console>:8: error: scrutinee is incompatible with pattern type;
 found   : Int
 required: String
       val (n: String, l: Int) = (4, "");
                          ^
<console>:8: error: type mismatch;
 found   : Int
 required: String
       val (n: String, l: Int) = (4, "");
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scabug commented Oct 22, 2011

Imported From: https://issues.scala-lang.org/browse/SI-5106?orig=1
Reporter: @jsalvata
Affected Versions: 2.9.0-1, 2.9.2
Other Milestones: 2.10.0

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scabug commented Oct 22, 2011

@jsalvata said:
This is different from SUGGEST-4 -- those throw MatchErrors, not ClassCastExceptions. And none of the examples there is so blatant.

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scabug commented May 3, 2012

@adriaanm said:
seems fixed in master:

scala> val (n, l): (String, Int) = (4, "")
<console>:7: error: type mismatch;
 found   : Int(4)
 required: String
       val (n, l): (String, Int) = (4, "")
                                    ^
<console>:7: error: type mismatch;
 found   : String("")
 required: Int
       val (n, l): (String, Int) = (4, "")
                                       ^

scala>  val (n: String, l: Int) = (4, "");
<console>:7: error: scrutinee is incompatible with pattern type;
 found   : String
 required: Int
        val (n: String, l: Int) = (4, "");
                ^
<console>:7: error: scrutinee is incompatible with pattern type;
 found   : Int
 required: String
        val (n: String, l: Int) = (4, "");

@scabug scabug closed this May 3, 2012

@scabug scabug added the patmat label Apr 7, 2017

@scabug scabug added this to the 2.10.0-M3 milestone Apr 7, 2017

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