diff --git a/compiler/src/dotty/tools/dotc/ast/Desugar.scala b/compiler/src/dotty/tools/dotc/ast/Desugar.scala
index 22b45e781a29..6406035d0678 100644
--- a/compiler/src/dotty/tools/dotc/ast/Desugar.scala
+++ b/compiler/src/dotty/tools/dotc/ast/Desugar.scala
@@ -1657,7 +1657,7 @@ object desugar {
         case pat @ Bind(nme.WILDCARD, body) =>
           val name =
             body match
-            case Typed(Ident(nme.WILDCARD), tpt) if pat.mods.is(Given) => inventGivenName(tpt)
+            case Typed(Ident(nme.WILDCARD), tpt) if pat.mods.is(Given) => inventGivenOrExtensionName(tpt)
             case _ => UniqueName.fresh()
           (cpy.Bind(pat)(name, body).withMods(pat.mods), Ident(name))
         case Bind(name, _) => (pat, Ident(name))
diff --git a/compiler/src/dotty/tools/dotc/transform/init/Checker.scala b/compiler/src/dotty/tools/dotc/transform/init/Checker.scala
index 6db759f60ad3..92f55f30edff 100644
--- a/compiler/src/dotty/tools/dotc/transform/init/Checker.scala
+++ b/compiler/src/dotty/tools/dotc/transform/init/Checker.scala
@@ -46,7 +46,7 @@ class Checker extends Phase:
     cancellable {
       val classes = traverser.getClasses()
 
-      if ctx.settings.Whas.safeInit then
+      if ctx.settings.Whas.checkInit then
         Semantic.checkClasses(classes)(using checkCtx)
     }
 
diff --git a/compiler/src/dotty/tools/dotc/typer/Implicits.scala b/compiler/src/dotty/tools/dotc/typer/Implicits.scala
index c7e7de0dc61a..dec4e703f63d 100644
--- a/compiler/src/dotty/tools/dotc/typer/Implicits.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Implicits.scala
@@ -790,7 +790,7 @@ 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/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
index cec2e93d4bf8..1fefa3c1183c 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -53,6 +53,7 @@ import config.Config
 import transform.CheckUnused.OriginalName
 
 import scala.annotation.constructorOnly
+import scala.util.chaining.scalaUtilChainingOps
 import dotty.tools.dotc.rewrites.Rewrites
 
 object Typer {
diff --git a/compiler/test/dotty/tools/dotc/reporting/CodeActionTest.scala b/compiler/test/dotty/tools/dotc/reporting/CodeActionTest.scala
index ed49ef1172b4..f3b03d14ca1c 100644
--- a/compiler/test/dotty/tools/dotc/reporting/CodeActionTest.scala
+++ b/compiler/test/dotty/tools/dotc/reporting/CodeActionTest.scala
@@ -4,6 +4,7 @@ import dotty.tools.DottyTest
 import dotty.tools.dotc.rewrites.Rewrites
 import dotty.tools.dotc.rewrites.Rewrites.ActionPatch
 import dotty.tools.dotc.util.SourceFile
+import dotty.tools.dotc.core.Contexts._
 
 import scala.annotation.tailrec
 import scala.jdk.CollectionConverters.*
@@ -295,8 +296,8 @@ class CodeActionTest extends DottyTest:
     val rep = new StoreReporter(null) with UniqueMessagePositions with HideNonSensicalMessages
     initialCtx.setReporter(rep).withoutColors
 
-  private def checkCodeAction(code: String, title: String, expected: String, afterPhase: String = "typer") =
-    ctx = newContext
+  private def checkCodeAction(code: String, title: String, expected: String, afterPhase: String = "typer", ctxx: Context = newContext) =
+    ctx = ctxx
     val source = SourceFile.virtual("test", code).content
     val runCtx = checkCompile(afterPhase, code) { (_, _) => () }
     val diagnostics = runCtx.reporter.removeBufferedMessages
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