From 3e792864055d720ec21a208e36a039fcd80f6712 Mon Sep 17 00:00:00 2001
From: Som Snytt <som.snytt@gmail.com>
Date: Sat, 1 Feb 2025 17:08:59 -0800
Subject: [PATCH 1/2] Status quo

---
 tests/warn/i21805.scala | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)
 create mode 100644 tests/warn/i21805.scala

diff --git a/tests/warn/i21805.scala b/tests/warn/i21805.scala
new file mode 100644
index 000000000000..f53b899c0176
--- /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.* // warn
+  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.* // warn
+    def test() = typeChecks("42 + 27")
+  package nok:
+    import scala.compiletime.testing.typeChecks // warn
+    def test() = typeChecks("42 + 27")
+
+@main def Test = println:
+  q.f(27)

From 2ac247ed32f3bcf6d6db79607069132616464817 Mon Sep 17 00:00:00 2001
From: Som Snytt <som.snytt@gmail.com>
Date: Mon, 22 Sep 2025 20:22:52 -0700
Subject: [PATCH 2/2] Ignore compiletime.testing for now

---
 compiler/src/dotty/tools/dotc/transform/CheckUnused.scala | 5 +++++
 tests/warn/i21805.scala                                   | 6 +++---
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/compiler/src/dotty/tools/dotc/transform/CheckUnused.scala b/compiler/src/dotty/tools/dotc/transform/CheckUnused.scala
index 1c6bae6b112a..913a2ad1829d 100644
--- a/compiler/src/dotty/tools/dotc/transform/CheckUnused.scala
+++ b/compiler/src/dotty/tools/dotc/transform/CheckUnused.scala
@@ -500,6 +500,7 @@ object CheckUnused:
         if inliners == 0
           && languageImport(imp.expr).isEmpty
           && !imp.isGeneratedByEnum
+          && !imp.isCompiletimeTesting
           && !ctx.owner.name.isReplWrapperName
         then
           imps.put(imp, ())
@@ -1031,6 +1032,10 @@ object CheckUnused:
     def isGeneratedByEnum: Boolean =
       imp.symbol.exists && imp.symbol.owner.is(Enum, butNot = Case)
 
+    /** 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
index f53b899c0176..4fdcae85910d 100644
--- a/tests/warn/i21805.scala
+++ b/tests/warn/i21805.scala
@@ -2,7 +2,7 @@
 
 def i23967: Boolean = {
   //import scala.compiletime.testing.typeCheckErrors
-  import scala.compiletime.testing.* // warn
+  import scala.compiletime.testing.* // nowarn
   typeChecks("2 + 2")
 }
 
@@ -21,10 +21,10 @@ package q:
 
 package i23967b:
   package ok:
-    import scala.compiletime.testing.* // warn
+    import scala.compiletime.testing.* // nowarn
     def test() = typeChecks("42 + 27")
   package nok:
-    import scala.compiletime.testing.typeChecks // warn
+    import scala.compiletime.testing.typeChecks // nowarn
     def test() = typeChecks("42 + 27")
 
 @main def Test = println: