Introduce KotlinMetadataFinder#hasMetadataPackage

Before creating a MetadataPackageFragment, check that the corresponding
directory (across the classpath) contains at least one .kotlin_metadata file.
Otherwise we're creating packages for every simple name queried during the
resolution and sometimes prefer a (empty) package to the existing class, for
example when the latter class is star-imported

core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/KotlinMetadataFinder.kt

@@ -27,6 +27,13 @@ interface KotlinMetadataFinder {
      */
     fun findMetadata(classId: ClassId): InputStream?
 
+    /**
+     * @return `true` iff this finder is able to locate the package with the given [fqName], containing .kotlin_metadata files.
+     * Note that returning `true` makes [MetadataPackageFragmentProvider] construct the package fragment for the package,
+     * and that fact can alter the qualified name expression resolution in the compiler front-end
+     */
+    fun hasMetadataPackage(fqName: FqName): Boolean
+
     /**
      * @return an [InputStream] which should be used to load the .kotlin_builtins file for package with the given [packageFqName].
      */

core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/MetadataPackageFragmentProvider.kt

@@ -60,7 +60,9 @@ class MetadataPackageFragmentProvider(
     }
 
     override fun findPackage(fqName: FqName): DeserializedPackageFragment? =
-            MetadataPackageFragment(fqName, storageManager, moduleDescriptor, packagePartProvider, finder)
+            if (finder.hasMetadataPackage(fqName))
+                MetadataPackageFragment(fqName, storageManager, moduleDescriptor, packagePartProvider, finder)
+            else null
 }
 
 class MetadataPackageFragment(