Do not propagate @tailrec to exported methods

Fixes #19505

Author: nicolasstucki

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

@@ -1254,7 +1254,10 @@ class Namer { typer: Typer =>
               newSymbol(cls, forwarderName, mbrFlags, mbrInfo, coord = span)
 
           forwarder.info = avoidPrivateLeaks(forwarder)
-          forwarder.addAnnotations(sym.annotations.filterConserve(_.symbol != defn.BodyAnnot))
+          forwarder.addAnnotations(sym.annotations.filterConserve { annot =>
+            annot.symbol != defn.BodyAnnot
+            && annot.symbol != defn.TailrecAnnot
+          })
 
           if forwarder.isType then
             buf += tpd.TypeDef(forwarder.asType).withSpan(span)

tests/pos/i19505.scala

@@ -0,0 +1,10 @@
+import scala.annotation.tailrec
+
+object Foo:
+  @tailrec
+  def foo(n: Int): Int =
+    if n == 0 then 0
+    else foo(n-1)
+
+object Bar:
+  export Foo.foo // def foo here should not have `@tailrec`

tests/warn/i19505.scala

@@ -0,0 +1,8 @@
+import scala.annotation.tailrec
+
+object Foo:
+  @tailrec
+  def foo: Int = foo // warn: Infinite recursive call
+
+object Bar:
+  export Foo.foo // def foo here should not have `@tailrec`