Fix StaleSymbol for path dependent argument type in macro context

To fix we recalculate the symbol from directly from NamedType when from
invalid run, instead of updating it's validity (which is impossible, as
its owners do not include it in their decls).

Author: jchyb

Diff for: compiler/src/dotty/tools/dotc/core/Types.scala

@@ -2754,14 +2754,16 @@ object Types {
     /** A reference like this one, but with the given prefix. */
     final def withPrefix(prefix: Type)(using Context): Type = {
       def reload(): NamedType = {
-        val lastSym = lastSymbol.nn
-        val allowPrivate = !lastSym.exists || lastSym.is(Private)
+        val sym =
+          if lastSymbol.nn.isValidInCurrentRun then lastSymbol.nn 
+          else computeSymbol
+        val allowPrivate = !sym.exists || sym.is(Private)
         var d = memberDenot(prefix, name, allowPrivate)
-        if (d.isOverloaded && lastSym.exists)
+        if (d.isOverloaded && sym.exists)
           d = disambiguate(d,
-                if (lastSym.signature == Signature.NotAMethod) Signature.NotAMethod
-                else lastSym.asSeenFrom(prefix).signature,
-                lastSym.targetName)
+                if (sym.signature == Signature.NotAMethod) Signature.NotAMethod
+                else sym.asSeenFrom(prefix).signature,
+                sym.targetName)
         NamedType(prefix, name, d)
       }
       if (prefix eq this.prefix) this

Diff for: tests/pos-macros/i17294/Bar.scala

@@ -0,0 +1,6 @@
+import scala.quoted.*
+
+class Bar[T]
+object Bar:
+  transparent inline def bar[T](a: Foo, b: a.Out): Bar[T] = ${ getBarMacro[T] }
+  def getBarMacro[T](using Quotes, Type[T]): Expr[Bar[T]] = '{ new Bar[T] }

Diff for: tests/pos-macros/i17294/Foo.scala

@@ -0,0 +1,3 @@
+class Foo:
+  type Out = Int
+val a = Bar.bar(new Foo(), 0)