Merge pull request #11733 from dotty-staging/fix-11725

Survive competing methods with select names _1, _2, ...

Author: bishabosha

compiler/src/dotty/tools/dotc/transform/SyntheticMembers.scala

@@ -174,7 +174,8 @@ class SyntheticMembers(thisPhase: DenotTransformer) {
     def productElementBody(arity: Int, index: Tree)(using Context): Tree = {
       // case N => _${N + 1}
       val cases = 0.until(arity).map { i =>
-        CaseDef(Literal(Constant(i)), EmptyTree, Select(This(clazz), nme.selectorName(i)))
+        val sel = This(clazz).select(nme.selectorName(i), _.info.isParameterless)
+        CaseDef(Literal(Constant(i)), EmptyTree, sel)
       }
 
       Match(index, (cases :+ generateIOBECase(index)).toList)

tests/pos/i11725.scala

@@ -0,0 +1,17 @@
+sealed trait Expr[+A] extends ExprTuple[A]
+
+case class Lit[A](value: A) extends Expr[A]
+
+trait ExprTuple[+A] {
+  def _1(implicit ev: ExprTuple.Has2[A]): Expr[ev._1] = ???
+  def _2(implicit ev: ExprTuple.Has2[A]): Expr[ev._2] = ???
+}
+
+object ExprTuple {
+  trait Has2[-A] { type _1; type _2 }
+  object Has2 {
+    type Aux[-A, A1, A2] = Has2[A] { type _1 = A1; type _2 = A2 }
+  }
+
+  implicit def tuple2[A, B]: Has2.Aux[(A, B), A, B] = ???
+}