Fix #7876: Hold off with uniqueness checking for imports

Hold off checking uniqueness of imports with checkNewOrShadowed until
we have verified that there is no outer package level definition that
trumps the conflicting imports.

Author: odersky

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

@@ -173,6 +173,16 @@ class Typer extends Namer
           previous
         }
 
+      /** Recurse in outer context. If final result is same as `previous`, check that it
+       *  is new or shadowed. This order of checking is necessary since an
+       *  outer package-level definition might trump two conflicting inner
+       *  imports, so no error should be issued in that case. See i7876.scala.
+       */
+      def recurAndCheckNewOrShadowed(previous: Type, prevPrec: BindingPrec, prevCtx: Context)(given Context): Type =
+        val found = findRefRecur(previous, prevPrec, prevCtx)
+        if found eq previous then checkNewOrShadowed(found, prevPrec)
+        else found
+
       def selection(imp: ImportInfo, name: Name, checkBounds: Boolean) =
         if imp.sym.isCompleting then
           ctx.warning(i"cyclic ${imp.sym}, ignored", posd.sourcePos)
@@ -322,11 +332,11 @@ class Typer extends Namer
             else if (isPossibleImport(NamedImport) && (curImport ne outer.importInfo)) {
               val namedImp = namedImportRef(curImport)
               if (namedImp.exists)
-                findRefRecur(checkNewOrShadowed(namedImp, NamedImport), NamedImport, ctx)(outer)
+                recurAndCheckNewOrShadowed(namedImp, NamedImport, ctx)(given outer)
               else if (isPossibleImport(WildImport) && !curImport.sym.isCompleting) {
                 val wildImp = wildImportRef(curImport)
                 if (wildImp.exists)
-                  findRefRecur(checkNewOrShadowed(wildImp, WildImport), WildImport, ctx)(outer)
+                  recurAndCheckNewOrShadowed(wildImp, WildImport, ctx)(given outer)
                 else {
                   updateUnimported()
                   loop(ctx)(outer)

tests/pos/i7876.scala

@@ -0,0 +1,6 @@
+object foo
+object bar
+
+import foo._, bar._
+
+object eq