Don't generate paths with outer accessors to stable references

In that case we can generate directly a reference without going though
an inner this proxy and an outer accessor.

Fixes #11914.

Author: odersky

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

@@ -522,9 +522,13 @@ class Inliner(call: tpd.Tree, rhsToInline: tpd.Tree)(using Context) {
     for ((level, selfSym) <- sortedProxies) {
       lazy val rhsClsSym = selfSym.info.widenDealias.classSymbol
       val rhs =
-        if (lastSelf.exists)
-          ref(lastSelf).outerSelect(lastLevel - level, selfSym.info)
-        else if (rhsClsSym.is(Module) && rhsClsSym.isStatic)
+        if lastSelf.exists then
+          selfSym.info match
+            case info: TermRef if info.isStable =>
+              ref(info)
+            case _ =>
+              ref(lastSelf).outerSelect(lastLevel - level, selfSym.info)
+        else if rhsClsSym.is(Module) && rhsClsSym.isStatic then
           ref(rhsClsSym.sourceModule)
         else
           inlineCallPrefix

tests/run/i11914.scala

@@ -0,0 +1,17 @@
+class Wrapper[E <: Throwable]:
+  object syntax:
+    extension [A <: Matchable](a: E | A)
+      transparent inline def foreach(f: A => Any): Unit =
+        a match
+          case e: E => ()
+          case a: A => f(a)
+
+  def _catch[A](a: => A): E | A =
+    try a
+    catch case e: E => e
+
+object throwables extends Wrapper[Throwable]
+import throwables.syntax.*
+
+@main def Test(): Unit =
+  for x <- throwables._catch(1/1) do println(x)