From 673263028aad932ad8eeb5fd3820177c7574563e Mon Sep 17 00:00:00 2001
From: Eugene Flesselle <eugene@flesselle.net>
Date: Wed, 6 Aug 2025 17:34:54 +0200
Subject: [PATCH] Fix implicit scope liftToAnchors for parameter lower bounds

Related to https://github.com/scala/scala3/pull/23672#event-19012454596
But we were dropping a lower bound in this case.
---
 compiler/src/dotty/tools/dotc/typer/Implicits.scala |  2 +-
 tests/pos/i21951b.scala                             | 12 ++++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)
 create mode 100644 tests/pos/i21951b.scala

diff --git a/compiler/src/dotty/tools/dotc/typer/Implicits.scala b/compiler/src/dotty/tools/dotc/typer/Implicits.scala
index fa5b1cbfe19e..b330e68ae5c5 100644
--- a/compiler/src/dotty/tools/dotc/typer/Implicits.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Implicits.scala
@@ -832,7 +832,7 @@ trait ImplicitRunInfo:
               WildcardType
             else
               seen += t
-              t.superType match
+              t.underlying match
                 case TypeBounds(lo, hi) =>
                   if lo.isBottomTypeAfterErasure then apply(hi)
                   else AndType.make(apply(lo), apply(hi))
diff --git a/tests/pos/i21951b.scala b/tests/pos/i21951b.scala
new file mode 100644
index 000000000000..30068b89d994
--- /dev/null
+++ b/tests/pos/i21951b.scala
@@ -0,0 +1,12 @@
+
+class A
+object A:
+  given A = ???
+
+class B[X]
+object B:
+  given g[T]: B[T] = ???
+
+object Test:
+  def foo[X >: A] = summon[X] // was error
+  def bar[F[T] >: B[T]] = summon[F[Int]] // was error