Use enclosing enclosingInlineds for empty call (#24281)

Fixes #24248 Adjust enclosing inlineds for inlined parameter, and do look-up in imports if tree position is enclosed by any enclosing inlined position (any intermediate position, not just outermost).

Author: som-snytt

compiler/src/dotty/tools/dotc/transform/CheckUnused.scala

@@ -55,7 +55,7 @@ class CheckUnused private (phaseMode: PhaseMode, suffix: String) extends MiniPha
  if tree.symbol.exists then
  // if in an inline expansion, resolve at summonInline (synthetic pos) or in an enclosing call site
  val resolving =
- tree.srcPos.isUserCode
+ tree.srcPos.isUserCode(using if tree.hasAttachment(InlinedParameter) then ctx.outer else ctx)
  || tree.srcPos.isZeroExtentSynthetic // take as summonInline
  if !ignoreTree(tree) then
  def loopOverPrefixes(prefix: Type, depth: Int): Unit =
@@ -156,6 +156,10 @@ class CheckUnused private (phaseMode: PhaseMode, suffix: String) extends MiniPha
  case _ =>
  tree
 
+ override def prepareForInlined(tree: Inlined)(using Context): Context =
+ if tree.inlinedFromOuterScope then
+ tree.expansion.putAttachment(InlinedParameter, ())
+ ctx
  override def transformInlined(tree: Inlined)(using Context): tree.type =
  transformAllDeep(tree.call)
  tree
@@ -495,6 +499,9 @@ object CheckUnused:
  /** Tree is LHS of Assign. */
  val AssignmentTarget = Property.StickyKey[Unit]
 
+ /** Tree is an inlined parameter. */
+ val InlinedParameter = Property.StickyKey[Unit]
+
  class PostTyper extends CheckUnused(PhaseMode.Aggregate, "PostTyper")
 
  class PostInlining extends CheckUnused(PhaseMode.Report, "PostInlining")
@@ -1063,7 +1070,7 @@ object CheckUnused:
  def isUserCode(using Context): Boolean =
  val inlineds = enclosingInlineds // per current context
  inlineds.isEmpty
- || inlineds.last.srcPos.sourcePos.contains(pos.sourcePos)
+ || inlineds.exists(_.srcPos.sourcePos.contains(pos.sourcePos)) // include intermediate inlinings or quotes
 
  extension [A <: AnyRef](arr: Array[A])
  // returns `until` if not satisfied

tests/warn/i24248/lib.scala

@@ -0,0 +1,18 @@
+
+import scala.quoted.*
+
+trait Thing
+object Stuff:
+ given Thing()
+
+object lib:
+ inline def m: Thing = ${ mImpl[Thing] }
+
+ def mImpl[T](using Quotes, Type[T]): Expr[T] =
+ import quotes.reflect.*
+ val thing = Implicits.search(TypeRepr.of[T]) match
+ case iss: ImplicitSearchSuccess => iss.tree.asExprOf[T]
+ '{
+ val res = $thing
+ res
+ }

tests/warn/i24248/test.scala

@@ -0,0 +1,6 @@
+//> using options -Werror -Wunused:all
+
+import Stuff.given
+
+@main def test = println:
+ lib.m