From @jdv

#OK
[jdv@​wieldy ~]$ perl6 -e 'sub infix​:<o1> ($a, $b) is export { say 1 };
sub infix​:<o2> ($a, $b) is tighter(&infix​:<o1>) is export { say 2 }; 1
o1 1 o2 1; say &[o1].prec; say &[o2].prec;'
2
1
prec => t=
prec => t@​=
[jdv@​wieldy ~]$

#NOT OK
[jdv@​wieldy ~]$ perl6 -e 'module m { sub infix​:<o1> ($a, $b) is export
{ say 1 }; sub infix​:<o2> ($a, $b) is tighter(&infix​:<o1>) is export {
say 2 }; }; import m; 1 o1 1 o2 1; say &[o1].prec; say &[o2].prec;'
1
2
prec => t=
prec => t=
[jdv@​wieldy ~]$

From @TimToady

The add_categorical method was assuming it was adding a fresh definition of an operator, not one borrowed from a module, so it overrode the existing precedence with the defaults, which are wrong if the existing precedence doesn't happen to match the default.

Fixed with bb598968c68bff2163322aea040bd81ec6097ae4

Test in fae390f38efad9e51d2224951d7eb3d47fe9b889

@TimToady - Status changed from 'new' to 'resolved'