Instantiate for invariance in paramInstances

Author: dwijnand

compiler/src/dotty/tools/dotc/core/TypeComparer.scala

@@ -3095,7 +3095,7 @@ class TrackingTypeComparer(initctx: Context) extends TypeComparer(initctx) {
     def paramInstances(canApprox: Boolean) = new TypeAccumulator[Array[Type]]:
       def apply(insts: Array[Type], t: Type) = t match
         case param @ TypeParamRef(b, n) if b eq caseLambda =>
-          def range1(tp: Type) = Range(tp, tp)
+          def range1(tp: Type) = if variance == 0 then tp else Range(tp, tp)
           insts(n) =
             if canApprox then
               approximation(param, fromBelow = variance >= 0, Int.MaxValue).simplified

tests/neg/i17149.scala

@@ -0,0 +1,18 @@
+type Ext1[S] = S match {
+  case Seq[t] => t
+}
+type Ext2[S] = S match {
+  case Seq[_] => Int
+}
+type Ext3[S] = S match {
+  case Array[t] => t
+}
+type Ext4[S] = S match {
+  case Array[_] => Int
+}
+def foo[T <: Seq[Any], A <: Array[B], B] =
+  summon[Ext1[T] =:= T]    // error
+  summon[Ext2[T] =:= Int]  // ok
+  summon[Ext3[A] =:= B]    // ok
+  summon[Ext4[A] =:= Int]  // ok
+

tests/neg/wildcard-match.scala

@@ -25,7 +25,7 @@ class C
 
 def f[X <: Box[C], Y <: Cov[C], Z <: Contrav[C]] =
   def a: BoxElem[X] = ???  // OK
-  val _: C = a // error
+  val _: C = a
 
   def a1: CovElem[Y] = ???
   val _: C = a1  // error

tests/pos/9890.scala

@@ -41,7 +41,7 @@ object Test {
   )
 
   //compiles fine
-  //summon[Col[ColFromPos[0], Sudoku1] =:= (x, 8, x,  5, x, x,  x, 3, 6)]
+  summon[Col[ColFromPos[0], Sudoku1] =:= (x, 8, x,  5, x, x,  x, 3, 6)]
 
   summon[TupleDedup[(x, 8, x,  5, x, x,  x, 3, 6), Nothing] =:= (x, 8, 5, 3, 6)]
   //but this doesn't

tests/neg/i15155.scala renamed to tests/pos/i15155.scala

@@ -7,5 +7,5 @@ type EnumValue[A <: Enumeration] = A match {
 
 // https://github.com/json4s/json4s/blob/355d8751391773e0d79d04402a4f9fb7bfc684ec/ext/src/main/scala/org/json4s/ext/EnumSerializer.scala#L25-L26
 class EnumSerializer[E <: Enumeration: ClassTag](enumeration: E) {
-  val EnumerationClass = classOf[EnumValue[E]] // error
+  val EnumerationClass = classOf[EnumValue[E]]
 }