Dotty Documentation


object Config
extends Object with Serializable

[-] Constructors

[-] Members

[+] final val LogPendingFindMemberThreshold : 9

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.

[+] final val LogPendingSubTypesThreshold : 50

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

[+] final val LogPendingUnderlyingThreshold : 50

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

[+] final val alignArgsInAnd : true

If this flag is set, and we compute T1[X1] & T2[X2] as a new upper bound of a constrained parameter, try to align the arguments 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#glbArgs.

[+] final val cacheAsSeenFrom : true
[+] final val cacheImplicitScopes : true
[+] final val cacheMatchReduced : true
[+] final val cacheMemberNames : true
[+] final val cacheMembersNamed : true
[+] final val checkBackendNames : false

Check that Name#toString is not called directly from backend by analyzing the stack trace of each toString call on names. This is very expensive, so not suitable for continuous testing. But it can be used to find a problem when running a specific test.

[+] final val checkCacheMembersNamed : false
[+] final val checkConstraintsNonCyclic : false

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

[+] final val checkConstraintsPropagated : false

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.

[+] final val checkConstraintsSatisfiable : false

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

[+] final val checkConstraintsSeparated : false

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.

[+] final val checkHKApplications : false

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

[+] final val checkLambdaVariance : false

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

[+] final val checkMethodTypes : false

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

[+] final val checkNoDoubleBindings : true

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.

[+] final val checkNoSkolemsInInfo : false

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

[+] final val checkPositions : true

Check positions for consistency after parsing

[+] final val checkTreesConsistent : false

Check that typed trees don't point to untyped ones

[+] final val checkTypeParamRefs : false

If this flag is set, it is checked that class type parameters are only references with NoPrefix or ThisTypes as prefixes. This option is usually disabled, because there are still some legitimate cases where this can arise (e.g. for pos/Map.scala, in LambdaType.integrate).

[+] final val checkTypeRefCycles : false

If this flag is set, it is checked that TypeRefs don't refer directly to themselves.

[+] final val checkUnerased : false

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.

[+] final val checkUnreportedErrors : false

If this flag is set, we check that types assigned to trees are error types only if some error was already reported. There are complicicated scenarios where this is not true. An example is TestNonCyclic in posTwice. If we remove the first (unused) import import in CompilationUnit, we end up assigning a CyclicReference error type to an import expression annotation before the cyclic reference is reported. What happens is that the error was reported as a result of a completion in a not-yet committed typerstate. So we cannot enforce this in all circumstances. But since it is almost always true it is useful to keep the Config option for debugging.

[+] final val debugCheckConstraintsClosed : false

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.

[+] final val failOnInstantiationToNothing : false

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 condition.

[+] final val fastPathForRefinedSubtype : true

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

[+] final val ignoreStaleInIDE : true

When in IDE, turn StaleSymbol errors into warnings instead of crashing

[+] final val initialUniquesCapacity : 65536

Initial capacity of uniques HashMap. Note: This MUST BE a power of two to work with util.HashSet

[+] final val showCompletions : false

If set, prints a trace of all symbol completions

[+] final val simplifyApplications : true

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.

[+] final val splitProjections : false

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.

[+] final val summarizeDepth : 2

The recursion depth for showing a summarized string

[+] final val traceDeepSubTypeRecursions : false

Show subtype traces for all deep subtype recursions

[+] final val tracingEnabled : false

If set, enables tracing

[+] final val verboseExplainSubtype : false

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