Fix #2429: fix true exhaustivity warnings

Author: liufengyun

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

@@ -351,15 +351,17 @@ class PatternMatcher extends MiniPhaseTransform with DenotTransformer {
       /* (Nil, body) means that `body` is the default case
        * It's a bit hacky but it simplifies manipulations.
        */
-      def extractSwitchCase(treeMakers: List[TreeMaker]): (List[Int], BodyTreeMaker) = treeMakers match {
+      def extractSwitchCase(treeMakers: List[TreeMaker]): (List[Int], BodyTreeMaker) = (treeMakers: @unchecked) match {
         // case 5 =>
         case List(IntEqualityTestTreeMaker(intValue), body: BodyTreeMaker) =>
           (List(intValue), body)
 
         // case 5 | 6 =>
         case List(AlternativesTreeMaker(_, alts, _), body: BodyTreeMaker) =>
-          val intValues = alts.map {
-            case List(IntEqualityTestTreeMaker(intValue)) => intValue
+          val intValues = alts.map { alt =>
+            (alt: @unchecked) match {
+              case List(IntEqualityTestTreeMaker(intValue)) => intValue
+            }
           }
           (intValues, body)
 

doc-tool/src/dotty/tools/dottydoc/model/comment/BodyEntities.scala

@@ -64,7 +64,7 @@ final case class Text(text: String) extends Inline
 abstract class EntityLink(val title: Inline) extends Inline { def link: LinkTo }
 object EntityLink {
   def apply(title: Inline, linkTo: LinkTo) = new EntityLink(title) { def link: LinkTo = linkTo }
-  def unapply(el: EntityLink): Option[(Inline, LinkTo)] = Some((el.title, el.link))
+  def unapply(el: EntityLink): Some[(Inline, LinkTo)] = Some((el.title, el.link))
 }
 final case class HtmlTag(data: String) extends Inline {
   private val Pattern = """(?ms)\A<(/?)(.*?)[\s>].*\z""".r

doc-tool/src/dotty/tools/dottydoc/staticsite/tags.scala

@@ -104,6 +104,10 @@ object tags {
         title
 
       case ConstantReference(title) => title
+
+      case _ =>  // EmptyReference
+        ctx.docbase.error(s"invalid reference: $ref")
+        null
     }
     override def render(tctx: TemplateContext, nodes: LNode*): AnyRef = nodes(0).render(tctx) match {
       case map: JMap[String, AnyRef] @unchecked =>

doc-tool/src/dotty/tools/dottydoc/util/MemberLookup.scala

@@ -77,6 +77,7 @@ trait MemberLookup {
       case (x :: xs, _) =>
         if (xs.nonEmpty) globalLookup
         else lookup(entity, packages, "scala." + query)
+      case (Nil, _) => ??? // impossible as long as query is not empty
     }
   }