Multiple assignment via pattern matching with Array is not working with uppercase vals

Question

After reading this answer I've tried to play with this nice feature by myself and found out that it is ok when I'm do

scala> val Array(a,b,n) = "XXX,YYY,ZZZ".split(",")
a: java.lang.String = XXX
b: java.lang.String = YYY
n: java.lang.String = ZZZ

But is not ok with uppercase named variable:

scala> val Array(a,b,N) = "XXX,YYY,ZZZ".split(",")
<console>:9: error: not found: value N
       val Array(a,b,N) = "XXX,YYY,ZZZ".split(",")

What is the reason of such behavior?

UPD Actually, the same thing with tuples assigment:

scala> val (a,b,N) = (1,2,3)
<console>:9: error: not found: value N
       val (a,b,N) = (1,2,3)

Answer 1

Scala treats it as a constant against which to match the pattern. Observe:

scala> val N = 20
N: Int = 20

scala> val Array(a, b, N) = Array(11, 23, 20)
a: Int = 11
b: Int = 23

scala> val Array(a, b, N) = Array(11, 23, 21)
scala.MatchError: [I@195d471 (of class [I)
        at .<init>(<console>:75)
        at .<clinit>(<console>)
        at .<init>(<console>:11)
        at .<clinit>(<console>)
        at $print(<console>)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at scala.tools.nsc.interpreter.IMain$ReadEvalPrint.call(IMain.scala:704)
        at scala.tools.nsc.interpreter.IMain$Request$$anonfun$14.apply(IMain.scala:920)
        at scala.tools.nsc.interpreter.Line$$anonfun$1.apply$mcV$sp(Line.scala:43)
        at scala.tools.nsc.io.package$$anon$2.run(package.scala:25)
        at java.lang.Thread.run(Thread.java:662)

The variables in which you want to extract the values must begin with a lower-case letter.