Minor refactorings related to PackagePartProvider and implementations

- Document what exactly should findPackageParts return
- Make EMPTY a named object instead of a val in the companion
- Do not use JvmPackagePartProvider in tests where Empty works fine
- Add a couple default values to arguments of setupResolverForProject

compiler/tests-common/org/jetbrains/kotlin/codegen/GenerationUtils.java

@@ -53,7 +53,7 @@ public class GenerationUtils {
     @NotNull
     public static GenerationState compileFiles(@NotNull List<KtFile> files, @Nullable KotlinCoreEnvironment environment) {
         PackagePartProvider packagePartProvider =
-                environment == null ? PackagePartProvider.Companion.getEMPTY() : new JvmPackagePartProvider(environment);
+                environment == null ? PackagePartProvider.Empty.INSTANCE : new JvmPackagePartProvider(environment);
         CompilerConfiguration configuration =
                 environment == null ? KotlinTestUtils.newConfiguration() : environment.getConfiguration();
 

compiler/tests-common/org/jetbrains/kotlin/resolve/lazy/lazyResolveTestUtils.kt

@@ -20,12 +20,10 @@ import com.intellij.openapi.project.Project
 import com.intellij.psi.search.GlobalSearchScope
 import org.jetbrains.kotlin.analyzer.ModuleContent
 import org.jetbrains.kotlin.analyzer.ModuleInfo
-import org.jetbrains.kotlin.builtins.DefaultBuiltIns
 import org.jetbrains.kotlin.container.get
 import org.jetbrains.kotlin.context.ProjectContext
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.psi.KtFile
-import org.jetbrains.kotlin.resolve.CompilerEnvironment
 import org.jetbrains.kotlin.resolve.jvm.JvmAnalyzerFacade
 import org.jetbrains.kotlin.resolve.jvm.JvmPlatformParameters
 
@@ -40,9 +38,7 @@ fun createResolveSessionForFiles(
             "test",
             projectContext, listOf(testModule),
             { ModuleContent(syntheticFiles, GlobalSearchScope.allScope(project)) },
-            JvmPlatformParameters { testModule },
-            CompilerEnvironment,
-            DefaultBuiltIns.Instance
+            JvmPlatformParameters { testModule }
     )
     return resolverForProject.resolverForModule(testModule).componentProvider.get<ResolveSession>()
 }