val 1 = 2 compiles

[scabug]

The following code should not compile.

scala> object Foo { val 1 = 2 }
defined module Foo

Also, as been pointed out by Seth Tisue, the defined val shadows the corresponding integer literal, producing unexpected behavior:

scala> object O { val 1 = 2; def x = 1 }
defined module O

scala> O.x
scala.MatchError: 2 (of class java.lang.Integer)

[scabug]

Imported From: https://issues.scala-lang.org/browse/SI-4939?orig=1
Reporter: @lexn82
Affected Versions: 2.9.0-1, 2.9.1

[scabug]

@paulp said:
"val 1 = 2" compiling is according to spec.

PatVarDef ::= ‘val’ PatDef
PatDef    ::= Pattern2 ‘=’ Expr
Pattern2  ::= Literal

It's not so according to spec that one can redefine the literal 1.

[scabug]

@paulp said:
Oh yeah, that's the object constructor throwing that exception. In that case it's all as expected.

[scabug]

@SethTisue said (edited on Aug 24, 2011 2:29:27 PM UTC):
Indeed, val definitions that don't bind any variables are actually explicitly speced. See SLS 4.1: "If p has no bound variables..."

There is much discussion of this issue at https://groups.google.com/forum/#!topic/scala-user/k57U6jt8Za0

Surely this is a bug though:

Welcome to Scala version 2.9.1.RC4 (Java HotSpot(TM) 64-Bit Server VM, Java 1.6.0_26).
Type in expressions to have them evaluated.
Type :help for more information.

scala> { val 1 = 2 }
scala.MatchError: 2 (of class java.lang.Integer)

scala> val 1 = 2

scala> 

No error there at the end, just "OK boss!"

Shall I open a separate ticket on it? Or shall we reopen this one?

[scabug]

@SethTisue said:
I opened #4950 on the REPL part of this.