Detect summon inline

Author: som-snytt

compiler/src/dotty/tools/dotc/reporting/Diagnostic.scala

@@ -112,5 +112,5 @@ class Diagnostic(
   override def diagnosticRelatedInformation: JList[interfaces.DiagnosticRelatedInformation] =
     Collections.emptyList()
 
-  override def toString: String = s"$getClass at $pos L${pos.line}: $message"
+  override def toString: String = s"$getClass at $pos L${pos.line+1}: $message"
 end Diagnostic

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

@@ -51,7 +51,12 @@ class CheckUnused private (phaseMode: PhaseMode, suffix: String) extends MiniPha
 
   override def transformIdent(tree: Ident)(using Context): tree.type =
     if tree.symbol.exists then
-      if !ignoreTree(tree) then
+      // resolve if inlined at the position of the call, or is zero extent summon
+      val resolving =
+           refInfos.inlined.isEmpty
+        || tree.srcPos.isZeroExtentSynthetic
+        || refInfos.inlined.exists(_.sourcePos.contains(tree.srcPos.sourcePos))
+      if resolving && !ignoreTree(tree) then
         resolveUsage(tree.symbol, tree.name, tree.typeOpt.importPrefix.skipPackageObject)
     else if tree.hasType then
       resolveUsage(tree.tpe.classSymbol, tree.name, tree.tpe.importPrefix.skipPackageObject)
@@ -108,8 +113,12 @@ class CheckUnused private (phaseMode: PhaseMode, suffix: String) extends MiniPha
     case _ =>
     tree
 
+  override def prepareForInlined(tree: Inlined)(using Context): Context =
+    refInfos.inlined.push(tree.call.srcPos)
+    ctx
   override def transformInlined(tree: Inlined)(using Context): tree.type =
-    if !tree.call.isEmpty then
+    val _ = refInfos.inlined.pop()
+    if !tree.call.isEmpty && phaseMode.eq(PhaseMode.Aggregate) then
       transformAllDeep(tree.call)
     tree
 
@@ -432,6 +441,7 @@ object CheckUnused:
           defs.addOne((tree.symbol, tree.srcPos))
 
     var isRepl = false // have we seen a REPL artifact? avoid import warning, for example
+    val inlined = Stack.empty[SrcPos] // enclosing call.srcPos of inlined code
   end RefInfos
 
   // Symbols already resolved in the given Context (with name and prefix of lookup)
@@ -809,6 +819,9 @@ object CheckUnused:
       || imp.expr.tpe.member(sel.name.toTermName).hasAltWith(_.symbol.isCanEqual)
     )
 
+  extension (pos: SrcPos)
+    def isZeroExtentSynthetic: Boolean = pos.span.isSynthetic && pos.span.start == pos.span.end
+
   // incredibly, there is no "sort in place" for array
   extension [A <: AnyRef](arr: Array[A])
     def sorta[B](f: A => B)(using ord: Ordering[B]): arr.type =

tests/warn/i15503kb/power.scala

@@ -0,0 +1,15 @@
+
+object Power:
+  import scala.concurrent.* // warn [taps mic]
+  import scala.math.pow as power
+  import scala.quoted.*
+  inline def powerMacro(x: Double, inline n: Int): Double = ${ powerCode('x, 'n) }
+  def powerCode(x: Expr[Double], n: Expr[Int])(using Quotes): Expr[Double] =
+    n match
+    case Expr(m) => unrolledPowerCode(x, m)
+    case _ => '{ power($x, $n.toDouble) }
+  def unrolledPowerCode(x: Expr[Double], n: Int)(using Quotes): Expr[Double] =
+    n match
+    case 0 => '{ 1.0 }
+    case 1 => x
+    case _ => '{ $x * ${ unrolledPowerCode(x, n - 1) } }

tests/warn/i15503kb/square.scala

@@ -0,0 +1,6 @@
+//> using options -Wunused:all
+
+object PowerUser:
+  import scala.concurrent.* // warn [taps mic]
+  import Power.*
+  def square(x: Double): Double = powerMacro(x, 2)