Initial size of superId table

How many recursive calls to findMember are performed before logging names starts Note: this threshold has to be chosen carefully. Too large, and programs like tests/pos/IterableSelfRec go into polynomial (or even exponential?) compile time slowdown. Too small and normal programs will cause the compiler to do inefficient operations on findMember. The current value is determined so that (1) IterableSelfRec still compiles in reasonable time (< 10sec) (2) Compiling dotty itself only causes small pending names lists to be generated (we measured at max 6 elements) and these lists are never searched with contains.

How many recursive calls to isSubType are performed before logging starts.

How many recursive calls to NamedType#underlying are performed before logging starts.

Maximal number of outstanding recursive calls to findMember before backing out when findMemberLimit is set.

If this flag is set, and we compute T1 { X = S1 } & T2 { X = S2 } as a new upper bound of a constrained parameter, try to align the refinements by computing S1 =:= S2 (which might instantiate type parameters). This rule is contentious because it cuts the constraint set.

For more info, see the comment in TypeComparer#distributeAnd.

When updating a constraint bound, check that the constrained parameter does not appear at the top-level of either of its bounds.

Check that each constraint is fully propagated. i.e. If P <: Q then the upper bound of P is a subtype of the upper bound of Q and the lower bound of Q is a subtype of the lower bound of P.

Check that each constraint resulting from a subtype test is satisfiable.

Make sure none of the bounds of a parameter in an OrderingConstraint contains this 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.

If this flag is set, higher-kinded applications are checked for validity

Check that variances of lambda arguments match the variance of the underlying lambda class.

If this flag is set, method types are checked for valid parameter references

Enable noDoubleDef checking if option "-YnoDoubleDefs" is set. The reason to have an option as well as the present global switch is that the noDoubleDef checking is done in a hotspot, and we do not want to incur the overhead of checking an option each time.

Check that no type appearing as the info of a SymDenotation contains skolem types.

Check positions for consistency after parsing

Check that certain types cannot be created in erasedTypes phases. Note: Turning this option on will get some false negatives, since it is possible that And/Or types are still created during erasure as the result of some operation on an existing type.

Check that constraints of globally committable typer states are closed. NOTE: When enabled, the check can cause CyclicReference errors because it traverses all elements of a type. Such failures were observed when compiling all of dotty together (source seems to be in GenBCode which accesses javac's settings.)

It is recommended to turn this option on only when chasing down a TypeParamRef instantiation error. See comment in Types.TypeVar.instantiate.

Type comparer will fail with an assert if the upper bound of a constrained parameter becomes Nothing. This should be turned on only for specific debugging as normally instantiation to Nothing is not an error consdition.

If this flag is set, take the fast path when comparing same-named type-aliases and types

Initial capacity of uniques HashMap

If this flag is on, always rewrite an application S[Ts] where S is an alias for [Xs] -> U to [Xs := Ts]U. Turning this flag on was observed to give a ~6% speedup on the JUnit test suite.

In derivedSelect, rewrite

(S & T)#A  -->  S#A & T#A
(S | T)#A  -->  S#A | T#A

Not sure whether this is useful. Preliminary measurements show a slowdown of about 7% for the build when this option is enabled.

The recursion depth for showing a summarized string

Show subtype traces for all deep subtype recursions

When explaining subtypes and this flag is set, also show the classes of the compared types.