diff options
| -rw-r--r-- | src/dotty/tools/dotc/config/Config.scala | 9 | ||||
| -rw-r--r-- | src/dotty/tools/dotc/core/ConstraintHandling.scala | 6 |
2 files changed, 9 insertions, 6 deletions
diff --git a/src/dotty/tools/dotc/config/Config.scala b/src/dotty/tools/dotc/config/Config.scala index 212defbbf..461a15ac8 100644 --- a/src/dotty/tools/dotc/config/Config.scala +++ b/src/dotty/tools/dotc/config/Config.scala @@ -15,11 +15,12 @@ object Config { */ final val checkConstraintsNonCyclic = false - /** Like `checkConstraintsNonCyclic`, but all constrained parameters - * are tested for direct or indirect dependencies, each time a - * constraint is added in TypeComparer. + /** Make sure none of the bounds in an OrderingConstraint contains + * another constrained parameter at its toplevel (i.e. as an operand + * of a combination of &'s and |'s.). The check is performed each time + * a new bound is added to the constraint. */ - final val checkConstraintsNonCyclicTrans = false + final val checkConstraintsSeparated = false /** Check that each constraint resulting from a subtype test * is satisfiable. diff --git a/src/dotty/tools/dotc/core/ConstraintHandling.scala b/src/dotty/tools/dotc/core/ConstraintHandling.scala index 07e048ab3..d25de9742 100644 --- a/src/dotty/tools/dotc/core/ConstraintHandling.scala +++ b/src/dotty/tools/dotc/core/ConstraintHandling.scala @@ -45,7 +45,7 @@ trait ConstraintHandling { } } } - if (Config.checkConstraintsNonCyclicTrans) + if (Config.checkConstraintsSeparated) assert(!occursIn(bound), s"$param occurs in $bound") val c1 = constraint.narrowBound(param, bound, isUpper) (c1 eq constraint) || { @@ -252,11 +252,13 @@ trait ConstraintHandling { * Some of the Ti are constrained parameters * * In each case we cannot record the relationship as an isLess, because - * of he outer |/&. But we should not leave it in the constraint either + * of the outer |/&. But we should not leave it in the constraint either * because that would risk making a parameter a subtype or supertype of a bound * where the parameter occurs again at toplevel, which leads to cycles * in the subtyping test. So we intentionally loosen the constraint in order * to keep it safe. A test case that demonstrates the problem is i864.scala. + * Turn Config.checkConstraintsSeparated on to get an accurate diagnostic + * of the cycle when it is created. */ def prune(bound: Type): Type = bound match { case bound: AndOrType => |