Filter pos by span not outer

Author: som-snytt

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

@@ -235,7 +235,7 @@ trait MessageRendering {
   def messageAndPos(dia: Diagnostic)(using Context): String = {
     import dia.*
     val pos1 = pos.nonInlined
-    val inlineStack = pos.inlinePosStack.filter(_ != pos1)
+    val inlineStack = pos.inlinePosStack.filterNot(pos1.coincidesWith(_))
     val maxLineNumber =
       if pos.exists then (pos1 :: inlineStack).map(_.endLine).max + 1
       else 0

compiler/src/dotty/tools/dotc/util/SourcePosition.scala

@@ -15,11 +15,16 @@ extends SrcPos, interfaces.SourcePosition, Showable:
 
   def sourcePos(using Context) = this
 
-  /** Is `that` a source position contained in this source position ?
+  /** Is `that` a source position contained in this source position?
    *  `outer` is not taken into account. */
   def contains(that: SourcePosition): Boolean =
     this.source == that.source && this.span.contains(that.span)
 
+  /** Is `that` a source position that coincides with this source position?
+   *  `outer` is not taken into account. */
+  def coincidesWith(that: SourcePosition): Boolean =
+    this.source == that.source && this.span == that.span
+
   def exists: Boolean = span.exists
 
   def lineContent: String = source.lineContent(point)