Unlink type when entering clashing package

Here we unlink the existing type that clashes with the package to be
entered into the symbol table, issue an error and the proceed to enter
the rest of the symbols.

My concern with this approach is what happens during typechecking
if other things reference the unlinked type.

1 files changed, 13 insertions, 2 deletions

diff --git a/src/dotty/tools/dotc/typer/Namer.scala b/src/dotty/tools/dotc/typer/Namer.scala
index 687de1e7a..22b5517dd 100644
--- a/src/dotty/tools/dotc/typer/Namer.scala
+++ b/src/dotty/tools/dotc/typer/Namer.scala
@@ -21,6 +21,7 @@ import Inferencing._
 import transform.ValueClasses._
 import TypeApplications._
 import language.implicitConversions
+import reporting.diagnostic.messages._
 
 trait NamerContextOps { this: Context =>
 
@@ -264,7 +265,7 @@ class Namer { typer: Typer =>
       def preExisting = ctx.effectiveScope.lookup(name)
       if (ctx.owner is PackageClass)
         if (preExisting.isDefinedInCurrentRun)
-          errorName(s"${preExisting.showLocated} is compiled twice")
+          errorName(s"${preExisting.showLocated} has already been compiled\nonce during this run")
         else name
       else
         if ((!ctx.owner.isClass || name.isTypeName) && preExisting.exists)
@@ -343,8 +344,18 @@ class Namer { typer: Typer =>
       case Select(qual: RefTree, _) => createPackageSymbol(qual).moduleClass
     }
     val existing = pkgOwner.info.decls.lookup(pid.name)
+
     if ((existing is Package) && (pkgOwner eq existing.owner)) existing
-    else ctx.newCompletePackageSymbol(pkgOwner, pid.name.asTermName).entered
+    else {
+      // If the name exists as type we should unlink the existing name from the
+      // scope, issue an error and continue, as usual:
+      val existingTpe = pkgOwner.info.decls.lookup(pid.name.toTypeName)
+      if (existingTpe != NoSymbol) {
+        ctx.error(PkgDuplicateSymbol(existingTpe), pid.pos)
+        pkgOwner.info.decls.openForMutations.unlink(existingTpe)
+      }
+      ctx.newCompletePackageSymbol(pkgOwner, pid.name.asTermName).entered
+    }
   }
 
   /** Expand tree and store in `expandedTree` */