Allow GADT constraining for quotes matching

Author: dwijnand

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

@@ -1855,6 +1855,9 @@ class TypeComparer(@constructorOnly initctx: Context) extends ConstraintHandling
         // This relaxed version is needed to correctly compare dependent function types.
         // See pos/i12211.scala.
         def isSubInfo(info1: Type, info2: Type, symInfo: Type): Boolean =
+          def allowGadt = info2 match
+            case TypeAlias(tp: TypeRef) => tp.symbol.name.isVarPattern // currently from quotes matching
+            case _                      => false
           info2 match
             case info2: MethodType =>
               info1 match
@@ -1863,8 +1866,8 @@ class TypeComparer(@constructorOnly initctx: Context) extends ConstraintHandling
                   matchingMethodParams(info1, info2, precise = false)
                   && isSubInfo(info1.resultType, info2.resultType.subst(info2, info1), symInfo1.resultType)
                   && sigsOK(symInfo1, info2)
-                case _ => inFrozenGadt { isSubType(info1, info2) }
-            case _ => inFrozenGadt { isSubType(info1, info2) }
+                case _ => inFrozenGadtIf(!allowGadt) { isSubType(info1, info2) }
+            case _ => inFrozenGadtIf(!allowGadt) { isSubType(info1, info2) }
 
         val info1 = m.info.widenExpr
         isSubInfo(info1, tp2.refinedInfo.widenExpr, m.symbol.info.orElse(info1))