Update implicit search

Author: noti0na1

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

@@ -35,6 +35,7 @@ import config.Printers.{implicits, implicitsDetailed}
 import collection.mutable
 import reporting._
 import annotation.tailrec
+import NullOpsDecorator._
 
 import scala.annotation.internal.sharable
 import scala.annotation.threadUnsafe
@@ -130,7 +131,9 @@ object Implicits:
             else if (mt.paramInfos.lengthCompare(1) == 0 && {
                   var formal = widenSingleton(mt.paramInfos.head)
                   if (approx) formal = wildApprox(formal)
-                  explore(argType relaxed_<:< formal.widenExpr)
+                  explore((argType relaxed_<:< formal.widenExpr) ||
+                    Nullables.convertUnsafeNulls &&
+                      argType.isUnsafelyConvertable(formal.widenExpr))
                 })
               Candidate.Conversion
             else

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

@@ -32,7 +32,7 @@ class Synthesizer(typer: Typer)(using @constructorOnly c: Context):
           case defn.ArrayOf(elemTp) =>
             val etag = typer.inferImplicitArg(defn.ClassTagClass.typeRef.appliedTo(elemTp), span)
             if etag.tpe.isError then EmptyTree else etag.select(nme.wrap)
-          case tp if hasStableErasure(tp) && !defn.isBottomClass(tp.typeSymbol) =>
+          case tp if hasStableErasure(tp) && !defn.isBottomClassAfterErasure(tp.typeSymbol) =>
             val sym = tp.typeSymbol
             val classTag = ref(defn.ClassTagModule)
             val tag =

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

@@ -3549,6 +3549,7 @@ class Typer extends Namer
               report.error(em"the result of an implicit conversion must be more specific than $pt", tree.srcPos)
             tree.cast(pt)
           else
+            // TODO: we don't need to second time search, need to modify Implicits more
             def normalSearch =
               searchTree(tree)(failure => tryUnsafeNullConver(cannotFind(failure)))
             treeTpe match {
@@ -3559,7 +3560,7 @@ class Typer extends Namer
                 searchTree(tree.cast(tpe1)) { _ => normalSearch }
               case _ =>
                 normalSearch
-          }
+            }
         else tryUnsafeNullConver(recover(NoMatchingImplicits))
       }
     }

tests/explicit-nulls/neg/null-classtag.scala

@@ -0,0 +1,8 @@
+def f = {
+  val a: Array[Null] = Array(null) // error: No ClassTag available for Null
+}
+
+def g = {
+  import scala.language.unsafeNulls
+  val a: Array[Null] = Array(null) // error: No ClassTag available for Null
+}

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

@@ -57,7 +57,7 @@ class S {
     n1(Array("a", "b"))
     n2(Array("a", "b"))
 
-    n0(Array(null)) // error
+    n0(Array[String](null)) // error
     n1(Array(null))
     n2(Array(null))
 

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

@@ -52,6 +52,41 @@ class S {
     val z8: Array[String | Null] | Null = y2 // error
   }
 
+  locally {
+    implicit def g(x: Array[String]): String = ???
+
+    val y1: Array[String] = ???
+    val y2: Array[String] | Null = ???
+    val y3: Array[String | Null] | Null = ???
+
+    y1: String
+    y2: String // error
+    y3: String // error
+
+    y1: String | Null
+    y2: String | Null // error
+    y3: String | Null // error
+  }
+
+  locally {
+    implicit def g(x: Array[String | Null]): String | Null = ???
+
+    val y1: Array[String] = ???
+    val y2: Array[String] | Null = ???
+    val y3: Array[String | Null] = ???
+    val y4: Array[String | Null] | Null = ???
+
+    y1: String // error
+    y2: String // error
+    y3: String // error
+    y4: String // error
+
+    y1: String | Null // error
+    y2: String | Null // error
+    y3: String | Null
+    y4: String | Null // error
+  }
+
   locally {
     given Conversion[String, Array[String]] = _ => ???
 
@@ -69,6 +104,22 @@ class S {
     val z8: Array[String | Null] | Null = y2 // error
   }
 
+  locally {
+    given Conversion[Array[String], String] = _ => ???
+
+    val y1: Array[String] = ???
+    val y2: Array[String] | Null = ???
+    val y3: Array[String | Null] | Null = ???
+
+    y1: String
+    y2: String // error
+    y3: String // error
+
+    y1: String | Null
+    y2: String | Null // error
+    y3: String | Null // error
+  }
+
   abstract class MyConversion[T] extends Conversion[T, Array[T]]
 
   locally {