From 44a746c2d5e0eb3ff725e8188aaa2ec8dc28be8c Mon Sep 17 00:00:00 2001
From: odersky <odersky@gmail.com>
Date: Sun, 9 Oct 2022 21:25:42 +0200
Subject: [PATCH 1/2] Don't propagate imports into inlined code

Imports are supposed to be resolved already, so they need not and should not
be copied into inlined code.

Fixes #16156, unfortuntely in the sense that it will not work.
---
 .../dotty/tools/dotc/inlines/Inliner.scala    |  3 +++
 tests/neg/i16156/Defs_1.scala                 | 25 +++++++++++++++++++
 tests/neg/i16156/Use_2.scala                  |  4 +++
 3 files changed, 32 insertions(+)
 create mode 100644 tests/neg/i16156/Defs_1.scala
 create mode 100644 tests/neg/i16156/Use_2.scala

diff --git a/compiler/src/dotty/tools/dotc/inlines/Inliner.scala b/compiler/src/dotty/tools/dotc/inlines/Inliner.scala
index bea42e82ce6f..c2a4f1d7aeb4 100644
--- a/compiler/src/dotty/tools/dotc/inlines/Inliner.scala
+++ b/compiler/src/dotty/tools/dotc/inlines/Inliner.scala
@@ -596,6 +596,9 @@ class Inliner(val call: tpd.Tree)(using Context):
           // reference to a private method is kept at runtime.
           cpy.Select(tree)(qual.asInstance(qual.tpe.widen), name)
 
+        case tree: ImportOrExport =>
+          EmptyTree
+
         case tree => tree
       },
       oldOwners = inlinedMethod :: Nil,
diff --git a/tests/neg/i16156/Defs_1.scala b/tests/neg/i16156/Defs_1.scala
new file mode 100644
index 000000000000..81a9d35f6461
--- /dev/null
+++ b/tests/neg/i16156/Defs_1.scala
@@ -0,0 +1,25 @@
+//import quotes.reflect._
+
+trait MyEncoder[T]:
+  def encode: String
+class Context:
+  inline def summonMyEncoder[T]: String =
+    ${ SummonEncoder.impl[T] }
+  implicit val encoderInstance: MyEncoder[String] =
+    new MyEncoder[String] { def encode = "blah" }
+end Context
+
+import scala.quoted._
+
+object SummonEncoder:
+  def impl[T: Type](using Quotes) =
+    import quotes.reflect._
+    Expr.summon[MyEncoder[T]] match
+      case Some(enc) => '{ $enc.encode }
+      case None      => report.throwError("can't do it")
+
+class Repo[T]:
+  val ctx = new Context
+  inline def summonEncoder = { import ctx._ // change to: import ctx.{given, _} for the given example
+    ctx.summonMyEncoder[T]
+  }
diff --git a/tests/neg/i16156/Use_2.scala b/tests/neg/i16156/Use_2.scala
new file mode 100644
index 000000000000..fe39d2423aa4
--- /dev/null
+++ b/tests/neg/i16156/Use_2.scala
@@ -0,0 +1,4 @@
+
+object Use:
+  val repo = new Repo[String]
+  val v = repo.summonEncoder // error happens here!

From 501dfcf04ee8775edb3984b29b0a142884e9cc51 Mon Sep 17 00:00:00 2001
From: odersky <odersky@gmail.com>
Date: Mon, 10 Oct 2022 20:58:30 +0200
Subject: [PATCH 2/2] Eliminate imports after cross version checks

... except for language imports. It looks this does not change the underlying issue
but it's good housekeeping anyway. The problem is that imports would not be transformed
in a phase like ExplicitOuter since Import is not by default handled in MegaPhase's
transform. As long as no-one checks this might not matter, but it's still weird. So
better to get rid of them before.
---
 .../dotty/tools/dotc/typer/CrossVersionChecks.scala    | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/compiler/src/dotty/tools/dotc/typer/CrossVersionChecks.scala b/compiler/src/dotty/tools/dotc/typer/CrossVersionChecks.scala
index 044dd7bb8528..da3608ae1cbc 100644
--- a/compiler/src/dotty/tools/dotc/typer/CrossVersionChecks.scala
+++ b/compiler/src/dotty/tools/dotc/typer/CrossVersionChecks.scala
@@ -8,7 +8,7 @@ import util.SrcPos
 import config.{ScalaVersion, NoScalaVersion, Feature, ScalaRelease}
 import MegaPhase.MiniPhase
 import scala.util.{Failure, Success}
-import ast.tpd
+import ast.{tpd, untpd}
 
 class CrossVersionChecks extends MiniPhase:
   import tpd.*
@@ -21,6 +21,11 @@ class CrossVersionChecks extends MiniPhase:
   override def runsAfterGroupsOf: Set[String] = Set(FirstTransform.name)
     // We assume all type trees except TypeTree have been eliminated
 
+  override def checkPostCondition(tree: Tree)(using Context): Unit = tree match
+    case tree: Import =>
+      assert(untpd.languageImport(tree.expr).nonEmpty, i"illegal tree: $tree")
+    case _ =>
+
   // Note: if a symbol has both @deprecated and @migration annotations and both
   // warnings are enabled, only the first one checked here will be emitted.
   // I assume that's a consequence of some code trying to avoid noise by suppressing
@@ -182,7 +187,8 @@ class CrossVersionChecks extends MiniPhase:
         case t: RefTree => checkUndesiredProperties(t.symbol, t.srcPos)
         case _ =>
       }
-      tree
+      if untpd.languageImport(tree.expr).isEmpty then EmptyTree
+      else tree
     case _ => tree
 
 end CrossVersionChecks