Backport "Discard poly-functions when trying to resolve overloading" to LTS

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

@@ -2214,13 +2214,13 @@ trait Applications extends Compatibility {
     case _ => (Nil, 0)
 
   /** Resolve overloading by mapping to a different problem where each alternative's
-   *  type is mapped with `f`, alternatives with non-existing types are dropped, and the
+   *  type is mapped with `f`, alternatives with non-existing types or symbols are dropped, and the
    *  expected type is `pt`. Map the results back to the original alternatives.
    */
   def resolveMapped(alts: List[TermRef], f: TermRef => Type, pt: Type)(using Context): List[TermRef] =
     val reverseMapping = alts.flatMap { alt =>
       val t = f(alt)
-      if t.exists then
+      if t.exists && alt.symbol.exists then
         val (trimmed, skipped) = trimParamss(t.stripPoly, alt.symbol.rawParamss)
         val mappedSym = alt.symbol.asTerm.copy(info = t)
         mappedSym.rawParamss = trimmed

tests/pos/i20176.scala

@@ -0,0 +1,12 @@
+type Accumulator[A]
+
+object Accumulator {
+
+  val usage =
+    use[Int]:
+      "asd"
+
+  inline def use[A](using DummyImplicit): [B] => Any => Any = ???
+
+  inline def use[A]: [B] => Any => Any = ???
+}