[Scala 3] tighten HKT wildcards (_ → ?)#869
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Targeted rewrites: Array[GenCodec[?]], Array[Class[?]], List[Case[?]], Opt[cborKey[?]], Opt[cborDiscriminator[?]], List[Field[?]], List[CborKeyInfo[?]], Array[GenCodec.OOOFieldsObjectCodec[?]], Array[OOOFieldsObjectCodec[?]], InputMetadata[?], BIterable[?], Transformed[?, ?]. Kind-parameter declarations (trait PolyCodec[C[_]], abstract class HasPolyGenCodec[C[_]], abstract class HasPolyGenObjectCodec[C[_]], trait PolyObjectCodec[C[_]], abstract class HasPolyGenObjectCodecWithDeps[D, C[_]], abstract class HasPolyGenCodecWithDeps[D, C[_]], trait GadtCodec[C[_]], abstract class HasGadtCodec[C[_]], trait CborAdtPolyInstances[C[_]], abstract class HasPolyCborCodec[C[_]]) preserved verbatim per Pitfall 3.
Targeted rewrites: Iterator[?], List[ParamMetadata[?]], Map[String, FunctionSignature[?]], Map[String, GetterSignature[?]]. Kind-parameter declarations (def materialize[M[_], Real], def materializeForApi[M[_], Real], trait RpcMetadataCompanion[M[_]], trait ApiMetadataCompanion[M[_]]) preserved verbatim per Pitfall 3.
Targeted rewrites: GenKeyCodec[TypeString[?]], GenCodec[TypeString[?]], GenKeyCodec[JavaClassName[?]], GenCodec[JavaClassName[?]], Entry[K, ?]*, Component[?], AtomicReference[?], MHashMap[Component[?], ...], MHashSet[Component[?]], AtomicReference[Future[?]]. Kind-parameter declarations (class TypedMap[K[_]], case class Entry[K[_], T], def pairToEntry[K[_], T], def empty[K[_]], def apply[K[_]], trait GenCodecMapping[K[_]], def typedMapCodec[K[_]], def instancesFor[TC[_], T], case class SelfInstance[C[_]], def materialize[C[_]], trait AdtMetadataCompanion[M[_]], trait MetadataCompanion[M[_]], type MColBuilder[Elem, +Col[_]], trait TupleDerivation[C[_]]) preserved verbatim per Pitfall 3.
Translated from origin/master@848b8e9e (mongo subset). Targeted rewrites: InputMetadata[?], MongoQueryOperator[?], MongoFilter[?], List[Case[?]], Map[Class[?], Case[?]], Map[Class[?], UnionFormat[?]], MHashMap[Class[?], (SealedParent[?], MListBuffer[Case[?]])], List[SealedParent[?]], Opt[Field[?]], List[Field[?]], Map[String, Field[?]], MongoCollection[?]. Kind-parameter declarations (final case class TypedMapFormat[K[_]], implicit def typedMapFormat[K[_]], implicit class typedMapFormatOps[K[_]], trait MongoPolyAdtInstances[D[_]], abstract class AbstractMongoPolyDataCompanion[Implicits, D[_]], abstract class MongoPolyDataCompanion[D[_]], implicit class TypedMapRefOps[E, K[_]], trait MongoFormatMapping[K[_]]) preserved verbatim per Pitfall 3.
…source-compat) Slice 3.2: `_` → `?` in applied positions across core + mongo. Kind-parameter declarations preserved. Pure type-argument-position syntax change; downstream callers unaffected.
… positions Prior sweep handled simple [_] / [_, _] applied positions. This polish catches remaining sites flagged by user 2026-06-01: - DocKey[A, _] / DocKey[_, _] / DocKey[_, _ <: BsonArray] → [A, ?] / [?, ?] / [?, ? <: BsonArray] in Filter, Sort, Update (object-level helpers) - BsonRef[_, T] / BsonRef[_, C[E]] / BsonRef[_, _] in mongo/core/ops/* (8 files) - DocKey[_, _] type ascriptions in KeyGetter - MongoRef[E, _], MongoRef[_, _], MongoPropertyRef[E, _], MongoToplevelRef[E, _] type ascriptions (parameter and return types only — type-patterns in case clauses preserved as `_` to mirror fork master shape) - MongoProjection[E, _] type ascription in ProjectionZippers Type-pattern wildcards in `case x: T[_, _]` clauses intentionally kept as `_` to match fork master @ origin/master (see MongoQueryOperator, MongoUpdate, MongoUpdateOperator, MongoRef.computePath/extractBson, MongoFormat.fieldRefFor). Per-file fork-shape comparison done; all applied-position rewrites mirror fork's canonical scala-3 form. Acceptance gate: every remaining [_]/[_ <: X] in scope is either a kind-decl position, a value-pattern wildcard, or a type-pattern in a case clause (fork- canonical). sbt compile Test/compile scalafmtCheckAll → exit 0, no new warnings, no @nowarn / -Wconf added.
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Slice: 3.2 of Phase 3 (Scala 3 syntax modernization)
Merge order: 3.1 → 3.2 → 3.3 → 3.4
Depends on: #868 (must merge first — slice 3.1 PR)
Base branch: upstream/scala-3 (not stacked on prior slice)
Summary
Applied-position HKT wildcards
[_]/[_, _]rewritten to[?]/[?, ?]per Scala 3 changed-features. Includes bounded existentials[_ <: X]/[_ >: X]→[? <: X]/[? >: X]. Kind-parameter declarations (class C[F[_]],def m[K[_]],case x: T[_, _], etc.) preserved verbatim — Scala 3 still uses_in kind-decl and type-pattern positions.Translated from
origin/master@848b8e9e(mongo subset).Commits (6, fork cadence — do not squash)
refactor(scala-3,core): F[_] → F[?] in applied positions (serialization)refactor(scala-3,core): F[_] → F[?] in applied positions (rpc)refactor(scala-3,core): F[_] → F[?] in applied positions (misc + di)refactor(scala-3,mongo): F[_] → F[?] in applied positions (sweep)refactor(scala-3,mongo): tighten HKT wildcards with bounds in applied positions— bounded-existential follow-up (50 rewrites across 18 mongo files: BsonRef, MongoRef, MongoPropertyRef, MongoOrder, MongoProjection, Filter.DocKey, etc.)docs(migration): record HKT wildcard tightening (type-level only, no source-compat)Source-compat impact
None.
F[?]vsF[_]is parse-level only — no call-site or downstream consumer effect. Pure type-argument-position syntax change.Verification
sbt compile ; Test/compile ; scalafmtCheckAll— exit 0core/src/main/scala,mongo/{jvm,js}/src/main/scala,hocon/src/main/scala— all remaining hits are kind-parameter declarations, type patterns (case x: T[_, _]), or scaladoc comments (manually verified per Pitfall 3 in slice planning).@nowarn/-Wconfintroduced.Notes on Pitfall 3 (kind-decl vs applied)
Kind-parameter declarations + type patterns preserved verbatim. Applied positions rewritten across 12 + 18 = 30 files.