Equi-joins not detected for conjunctions of equalities in predicates

[ghislainfourny]

for $a in $aa
for $b in $bb[$$.foo eq $a.foo and $$.bar eq $a.bar]
...

for $a in $aa
for $b allowing empty in $bb[$$.foo eq $a.foo and $$.bar eq $a.bar]
...

for $a in $aa
let $b := $bb[$$.foo eq $a.foo and $$.bar eq $a.bar]
...