avoid stripping type variables in OrderingConstraint.replace

Author: Linyxus

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

@@ -445,7 +445,7 @@ class OrderingConstraint(private val boundsMap: ParamBounds,
    *  of the parameter elsewhere in the constraint by type `tp`.
    */
   def replace(param: TypeParamRef, tp: Type)(using Context): OrderingConstraint =
-    val replacement = tp.dealiasKeepAnnots.stripTypeVar
+    val replacement = tp.dealiasKeepAnnots
     if param == replacement then this.checkNonCyclic()
     else
       assert(replacement.isValueTypeOrLambda)

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

@@ -436,7 +436,8 @@ object Inferencing {
     }
 
     // We add the created symbols to GADT constraint here.
-    if (res.nonEmpty) ctx.gadt.addToConstraint(res)
+    if res.nonEmpty then ctx.gadt.addToConstraint(res)
+
     res
   }
 

tests/neg/pdgadt-wildcard.scala

@@ -0,0 +1,20 @@
+trait Expr { type T }
+case class Inv[X](x: X) extends Expr { type T = X }
+case class Inv2[X](x: X) extends Expr { type T >: X }
+
+def eval(e: Expr): e.T = e match
+  case Inv(x) => x
+  case Inv2(x) => x
+
+trait Foo[-T]
+case class Bar() extends Foo[Int]
+
+def foo(e1: Expr, e2: Foo[e1.T]) = e1 match {
+  case Inv2(x) => e2 match {
+    case Bar() =>
+      val t0: Int = x
+      val t1: e1.T = x
+      val t2: Int = t1
+  }
+}
+