From 067e096bf9dacea5742ddad3324b22db51923e3b Mon Sep 17 00:00:00 2001
From: Som Snytt <som.snytt@gmail.com>
Date: Wed, 15 Oct 2025 10:36:35 -0700
Subject: [PATCH 1/2] Ignore compiletime.testing for now Import of
 compiletime.testing nullifies unused lint

---
 .../tools/dotc/transform/CheckUnused.scala    |  5 +++
 tests/warn/i21805.scala                       | 31 +++++++++++++++++++
 2 files changed, 36 insertions(+)
 create mode 100644 tests/warn/i21805.scala

diff --git a/compiler/src/dotty/tools/dotc/transform/CheckUnused.scala b/compiler/src/dotty/tools/dotc/transform/CheckUnused.scala
index 11a4f33cb9ba..2e870f447893 100644
--- a/compiler/src/dotty/tools/dotc/transform/CheckUnused.scala
+++ b/compiler/src/dotty/tools/dotc/transform/CheckUnused.scala
@@ -433,6 +433,7 @@ object CheckUnused:
         if inliners == 0
           && languageImport(imp.expr).isEmpty
           && !imp.isGeneratedByEnum
+          && !imp.isCompiletimeTesting
           && !ctx.owner.name.isReplWrapperName
         then
           imps.put(imp, ())
@@ -990,6 +991,10 @@ object CheckUnused:
       then imp.expr.tpe.allMembers.exists(_.symbol.isCanEqual)
       else imp.expr.tpe.member(sel.name.toTermName).hasAltWith(_.symbol.isCanEqual)
 
+    /** No mechanism for detection yet. */
+    def isCompiletimeTesting: Boolean =
+      imp.expr.symbol == defn.CompiletimeTestingPackage//.moduleClass
+
   extension (pos: SrcPos)
     def isZeroExtentSynthetic: Boolean = pos.span.isSynthetic && pos.span.isZeroExtent
     def isSynthetic: Boolean = pos.span.isSynthetic && pos.span.exists
diff --git a/tests/warn/i21805.scala b/tests/warn/i21805.scala
new file mode 100644
index 000000000000..4fdcae85910d
--- /dev/null
+++ b/tests/warn/i21805.scala
@@ -0,0 +1,31 @@
+//> using options -Wunused:imports
+
+def i23967: Boolean = {
+  //import scala.compiletime.testing.typeCheckErrors
+  import scala.compiletime.testing.* // nowarn
+  typeChecks("2 + 2")
+}
+
+package p:
+  val code = """"hello, world""""
+package c:
+  class C(i: Int)
+
+package q:
+  import c.* // warn should be nowarn
+  import p.* // warn should be nowarn
+  import scala.compiletime.testing.*
+  def test() = typeCheckErrors("""println(C("hello, world"))""")
+  def ok() = typeChecks("println(code)")
+  inline def f(inline i: Int) = 42 + i
+
+package i23967b:
+  package ok:
+    import scala.compiletime.testing.* // nowarn
+    def test() = typeChecks("42 + 27")
+  package nok:
+    import scala.compiletime.testing.typeChecks // nowarn
+    def test() = typeChecks("42 + 27")
+
+@main def Test = println:
+  q.f(27)

From 18f1a570a0e9c9b2220da238183ca4f422d63bc7 Mon Sep 17 00:00:00 2001
From: Wojciech Mazur <wmazur@virtuslab.com>
Date: Wed, 22 Oct 2025 14:42:47 +0200
Subject: [PATCH 2/2] Import of compiletime.testing nullifies unused lint

[Cherry-picked b3256812e6da4cba643a2685ce606ded40374acf][modified]