Scope of pattern variables in join clause

[gafter]

The expression in a join clause, i.e. e in ... join x in e ..., does not turn into a lambda body. This expression needs to define a scope for any pattern variables that are declared in that expression. The scope of those pattern variables does not extend outside that expression.

[AlekseyTs]

I disagree with this. Given that

A query expression with a join clause without an into followed by a select clause
from x1 in e1
join x2 in e2 on k1 equals k2
select v
is translated into
( e1 ) . Join( e2 , x1 => k1 , x2 => k2 , ( x1 , x2 ) => v )
A query expression with a join clause without an into followed by something other than a select clause
from x1 in e1
join x2 in e2 on k1 equals k2 
…
is translated into
from * in ( e1 ) . Join(
    e2 , x1 => k1 , x2 => k2 , ( x1 , x2 ) => new { x1 , x2 })
…
A query expression with a join clause with an into followed by a select clause
from x1 in e1
join x2 in e2 on k1 equals k2 into g
select v
is translated into
( e1 ) . GroupJoin( e2 , x1 => k1 , x2 => k2 , ( x1 , g ) => v )
A query expression with a join clause with an into followed by something other than a select clause
from x1 in e1
join x2 in e2 on k1 equals k2 into g
…
is translated into
from * in ( e1 ) . GroupJoin(
    e2 , x1 => k1 , x2 => k2 , ( x1 , g ) => new { x1 , g })

e2 should share scope with the scope that contains entire query expression, similar to e1.

[gafter]

@AlekseyTs Sounds good to me. I like your proposed scope rule here.