Fix OfType Implicits Search in UnsafeNulls

Author: noti0na1

compiler/src/dotty/tools/dotc/typer/Implicits.scala

@@ -280,11 +280,18 @@ object Implicits:
       buf.toList
     }
 
+    @threadUnsafe lazy val eligibleCache: List[Candidate] = filterMatching(tp)
+
+    @threadUnsafe lazy val eligibleCacheUnsafeNulls: List[Candidate] =
+      inContext(ctx.addMode(Mode.UnsafeNullConversion)) {
+          filterMatching(tp)
+      }
+
     /** The candidates that are eligible for expected type `tp` */
-    @threadUnsafe lazy val eligible: List[Candidate] =
+    def eligible(enableUnsafeNulls: Boolean): List[Candidate] =
       trace(i"eligible($tp), companions = ${companionRefs.showAsList}%, %", implicitsDetailed, show = true) {
         if (refs.nonEmpty && monitored) record(s"check eligible refs in tpe", refs.length)
-        filterMatching(tp)
+        if enableUnsafeNulls then eligibleCacheUnsafeNulls else eligibleCache
       }
 
     override def isAccessible(ref: TermRef)(using Context): Boolean =
@@ -1287,7 +1294,7 @@ trait Implicits:
     private def searchImplicit(contextual: Boolean): SearchResult =
       val eligible =
         if contextual then ctx.implicits.eligible(wildProto, ctx.mode.is(Mode.UnsafeNullConversion))
-        else implicitScope(wildProto).eligible
+        else implicitScope(wildProto).eligible(ctx.mode.is(Mode.UnsafeNullConversion))
       searchImplicit(eligible, contextual) match
         case result: SearchSuccess =>
           result
@@ -1330,7 +1337,8 @@ trait Implicits:
     def allImplicits: Set[TermRef] = {
       val contextuals = ctx.implicits.eligible(wildProto, ctx.mode.is(Mode.UnsafeNullConversion))
         .map(tryImplicit(_, contextual = true))
-      val inscope = implicitScope(wildProto).eligible.map(tryImplicit(_, contextual = false))
+      val inscope = implicitScope(wildProto).eligible(ctx.mode.is(Mode.UnsafeNullConversion))
+        .map(tryImplicit(_, contextual = false))
       (contextuals.toSet ++ inscope).collect {
         case success: SearchSuccess => success.ref
       }

compiler/src/dotty/tools/dotc/typer/ImportSuggestions.scala

@@ -159,7 +159,7 @@ trait ImportSuggestions:
       val wildProto = wildApprox(pt)
       val contextualCandidates = ctx.implicits.eligible(wildProto, ctx.mode.is(Mode.UnsafeNullConversion))
       val implicitScopeCandidates = ctx.run.implicitScope(wildProto).eligible
-      val allCandidates = contextualCandidates ++ implicitScopeCandidates
+      val allCandidates = contextualCandidates ++ implicitScopeCandidates(ctx.mode.is(Mode.UnsafeNullConversion))
       allCandidates.map(_.implicitRef.underlyingRef.symbol).toSet
     }
 

tests/explicit-nulls/pos/unpickler.scala

@@ -0,0 +1,5 @@
+// Ensure we don't have cyclic complete
+
+import scala.collection.immutable.BitSet
+
+val e = BitSet.empty

tests/explicit-nulls/unsafe-common/unsafe-implicit.scala

@@ -47,4 +47,13 @@ class S {
     f1 // error
     f2
   }
+
+  locally {
+    // OfType Implicits
+
+    import java.nio.charset.StandardCharsets
+    import scala.io.Codec
+
+    val c: Codec = StandardCharsets.UTF_8 // error
+  }
 }