Do not expose ClassInfo in memberType in reflect API

compiler/src/scala/quoted/runtime/impl/QuotesImpl.scala

@@ -1826,7 +1826,33 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
         def termSymbol: Symbol = self.termSymbol
         def isSingleton: Boolean = self.isSingleton
         def memberType(member: Symbol): TypeRepr =
-          member.info.asSeenFrom(self, member.owner)
+          // This check only fails if no owner of the passed symbol is related to the `self` type
+          // Ideally we would just check if the symbol is a member of the type,
+          // but:
+          //  A) the children of enums are not members of those enums, which is unintuitive
+          //  B) this check was added late, risking major hard to fix regressions
+          //     (including in compilation tests)
+          // Additionally, it's useful to be able to learn a type of a symbol using some prefix,
+          // even if it's not a direct member of that prefix, but e.g. a nested one.
+          def isTypePrefixingPassedMember =
+            import scala.util.boundary
+            boundary {
+              var checked: Symbol = member
+              while(checked.exists) {
+                if self.derivesFrom(checked)
+                || self.typeSymbol.declarations.contains(checked)
+                || self.typeSymbol.companionClass.declarations.contains(checked) then
+                  boundary.break(true)
+                checked = checked.owner
+              }
+              boundary.break(false)
+            }
+          xCheckMacroAssert(isTypePrefixingPassedMember, s"$member is not a member of ${self.show}")
+          // We do not want to expose ClassInfo in the reflect API, instead we change it to a TypeRef,
+          // see issue #22395
+          member.info.asSeenFrom(self, member.owner) match
+            case dotc.core.Types.ClassInfo(prefix, sym, _, _, _) => prefix.select(sym)
+            case other => other
         def baseClasses: List[Symbol] = self.baseClasses
         def baseType(cls: Symbol): TypeRepr = self.baseType(cls)
         def derivesFrom(cls: Symbol): Boolean = self.derivesFrom(cls)

tests/neg-macros/i15159.check

@@ -0,0 +1,17 @@
+
+-- Error: tests/neg-macros/i15159/Test_2.scala:5:16 --------------------------------------------------------------------
+5 |  TestMacro.test[A] // error
+  |  ^^^^^^^^^^^^^^^^^
+  |  Exception occurred while executing macro expansion.
+  |  java.lang.AssertionError: class X is not a member of A
+  |  	at TestMacro$.testImpl$$anonfun$1(Macro_1.scala:8)
+  |  	at scala.collection.immutable.List.map(List.scala:247)
+  |  	at TestMacro$.testImpl(Macro_1.scala:7)
+  |
+  |---------------------------------------------------------------------------------------------------------------------
+  |Inline stack trace
+  |- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+  |This location contains code that was inlined from Macro_1.scala:3
+3 |  inline def test[T]: Unit = ${ testImpl[T] }
+  |                             ^^^^^^^^^^^^^^^^
+   ---------------------------------------------------------------------------------------------------------------------

tests/neg-macros/i15159/Macro_1.scala

@@ -0,0 +1,10 @@
+import scala.quoted.*
+object TestMacro:
+  inline def test[T]: Unit = ${ testImpl[T] }
+  def testImpl[T: Type](using Quotes): Expr[Unit] =
+    import quotes.reflect.*
+    val tpe = TypeRepr.of[T]
+    tpe.typeSymbol.children.map { childSymbol =>
+      tpe.memberType(childSymbol) // not a member of tpe
+    }
+    '{ () }

tests/neg-macros/i15159/Test_2.scala

@@ -0,0 +1,6 @@
+sealed trait A
+case class X(i: Int) extends A
+
+object Test extends App {
+  TestMacro.test[A] // error
+}

tests/pos-macros/i13319/Macro_1.scala

@@ -0,0 +1,12 @@
+import scala.quoted._
+object Macro:
+  inline def apply[A]: Unit = ${impl[A]}
+
+  private def impl[A: Type](using Quotes): Expr[String] =
+    import quotes.reflect._
+    val t = TypeRepr.of[A]
+    Expr.ofList(t.baseClasses.drop(1).filter(_.flags.is(Flags.Trait)).map { baseSymbol =>
+        t.memberType(baseSymbol).asType  match { case '[t] => 42}
+        Expr("")
+    })
+    Expr("")

tests/pos-macros/i13319/Test_2.scala

@@ -0,0 +1 @@
+@main def Test = Macro[Option[String]]

tests/run-macros/i22395.check

@@ -0,0 +1 @@
+TypeRef(AppliedType(TypeRef(ThisType(TypeRef(ThisType(TypeRef(NoPrefix,module class <root>)),module class <empty>)),Foo),List(TypeRef(TermRef(ThisType(TypeRef(NoPrefix,module class <root>)),object scala),Int))),class Nested)

tests/run-macros/i22395/Macro_1.scala

@@ -0,0 +1,14 @@
+import scala.quoted._
+
+inline def test(): String = ${testImpl}
+def testImpl(using Quotes) = {
+  import quotes.reflect._
+  val fooSymbol = TypeRepr.of[Foo[Int]].typeSymbol
+  val nestedSymbol = fooSymbol.typeMember("Nested")
+
+  Expr(TypeRepr.of[Foo[Int]].memberType(nestedSymbol).toString)
+}
+
+
+trait Foo[X]:
+  sealed abstract class Nested extends Foo[Int]

tests/run-macros/i22395/Test_2.scala

@@ -0,0 +1,2 @@
+@main def Test =
+  println(test())