Can one of the admins verify this patch?

Given SI-9027, I think it's better to roll back #1671 and ask the user to use semicolon or xml:group rather than rolling out our own lexers.

scala> val xs: xml.NodeSeq = <xml:group><x/><y/></xml:group>
xs: scala.xml.NodeSeq = <x/><y/>

scala> :pa
// Entering paste mode (ctrl-D to finish)

val g = <xml:group><a/><b/></xml:group>
val b = <a/><b/>;
val c = (<a/><b/>)
val a = <a/><b/>


// Exiting paste mode, now interpreting.

g: scala.xml.Group = <a/><b/>
b: scala.xml.NodeBuffer = ArrayBuffer(<a/>, <b/>)
c: scala.xml.NodeBuffer = ArrayBuffer(<a/>, <b/>)
a: scala.xml.NodeBuffer = ArrayBuffer(<a/>, <b/>)


scala> a == b
res4: Boolean = true

scala> a == c
res5: Boolean = true

scala> a == g
res6: Boolean = false

Group is not the same as NodeBuffer.

Second problem is that how to detect xml compilation problem?

See

scala> :pa
// Entering paste mode (ctrl-D to finish)

val b = <a/><b/>
val s = 3

// Exiting paste mode, now interpreting.

<console>:2: error: ';' expected but 'val' found.
val s = 3
^

So the problem will be how to detect, that compilation problem is xml group compilation error?

@jsuereth @eed3si9n - we need use 2.10.4 in current sbt by at least 4 months. See scala/scala#4186 (comment)

My preference is to tell user to put semicolon or parens when they see error: ';' expected but 'val' found. rather than trying to implement our own lexer. As #1738 has shown, workarounds can cause more issues. Even though it is several months away, a definitive fix is coming up anyway.

As per NodeBuffer vs Group, if they behave the same semantically as NodeSeq, I am ok with them not being equal, but just to be safe we can recommend semicolon or parens instead of xml:group.

OK, so I have to change some tests as well.