Harden typedPackageDef

Author: odersky

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -1626,16 +1626,16 @@ class Typer extends Namer
   def typedPackageDef(tree: untpd.PackageDef)(implicit ctx: Context): Tree = track("typedPackageDef") {
     val pid1 = typedExpr(tree.pid, AnySelectionProto)(ctx.addMode(Mode.InPackageClauseName))
     val pkg = pid1.symbol
-
-    // Package will not exist if a duplicate type has already been entered, see
-    // `tests/neg/1708.scala`, else branch's error message should be supressed
-    if (pkg.exists) {
-      if (!pkg.is(Package)) ctx.error(PackageNameAlreadyDefined(pkg), tree.pos)
-      val packageCtx = ctx.packageContext(tree, pkg)
-      val stats1 = typedStats(tree.stats, pkg.moduleClass)(packageCtx)
-      cpy.PackageDef(tree)(pid1.asInstanceOf[RefTree], stats1) withType pkg.termRef
+    pid1 match {
+      case pid1: RefTree if pkg.exists =>
+        if (!pkg.is(Package)) ctx.error(PackageNameAlreadyDefined(pkg), tree.pos)
+        val packageCtx = ctx.packageContext(tree, pkg)
+        val stats1 = typedStats(tree.stats, pkg.moduleClass)(packageCtx)
+        cpy.PackageDef(tree)(pid1, stats1).withType(pkg.termRef)
+      case _ =>
+        // Package will not exist if a duplicate type has already been entered, see `tests/neg/1708.scala`
+        errorTree(tree, i"package ${tree.pid.name} does not exist")
     }
-    else errorTree(tree, i"package ${tree.pid.name} does not exist")
   }
 
   def typedAnnotated(tree: untpd.Annotated, pt: Type)(implicit ctx: Context): Tree = track("typedAnnotated") {

tests/neg/parser-stability-22.scala

@@ -0,0 +1,3 @@
+package x0.x0 {}
+object x0 {
+    def x0 (implicit  // error // error