Modules with different language levels can't be analyzed together

"Supports additional builtIn members" setting
    is basically adding members to some types
If we analyze them toghether other modules would leak types
    that have those members (or don't) into other modules scopes
    leading to code that has erroneous highlighting

See KT-17357

#KT-17357 Fixed

idea/tests/org/jetbrains/kotlin/idea/caches/resolve/MultiModuleHighlightingTest.kt

@@ -16,15 +16,21 @@
 
 package org.jetbrains.kotlin.idea.caches.resolve
 
+import com.intellij.facet.FacetManager
 import com.intellij.openapi.module.Module
 import com.intellij.openapi.roots.DependencyScope
 import com.intellij.openapi.vfs.newvfs.impl.VfsRootAccess
 import org.jetbrains.kotlin.analyzer.ModuleInfo
 import org.jetbrains.kotlin.analyzer.ResolverForModuleComputationTracker
+import org.jetbrains.kotlin.cli.common.arguments.K2JVMCompilerArguments
 import org.jetbrains.kotlin.codegen.forTestCompile.ForTestCompileRuntime
 import org.jetbrains.kotlin.config.JvmTarget
+import org.jetbrains.kotlin.config.LanguageVersion
 import org.jetbrains.kotlin.config.TargetPlatformKind
 import org.jetbrains.kotlin.idea.completion.test.withServiceRegistered
+import org.jetbrains.kotlin.idea.facet.KotlinFacetConfiguration
+import org.jetbrains.kotlin.idea.facet.KotlinFacetType
+import org.jetbrains.kotlin.idea.util.application.runWriteAction
 import org.jetbrains.kotlin.test.KotlinTestUtils
 
 class MultiModuleHighlightingTest : AbstractMultiModuleHighlightingTest() {
@@ -107,6 +113,34 @@ class MultiModuleHighlightingTest : AbstractMultiModuleHighlightingTest() {
         checkHighlightingInAllFiles()
     }
 
+    fun testLanguageVersionsViaFacets() {
+        val m1 = module("m1", useFullJdk = true).setupKotlinFacet {
+            settings.languageLevel = LanguageVersion.KOTLIN_1_1
+        }
+        val m2 = module("m2", useFullJdk = true).setupKotlinFacet {
+            settings.languageLevel = LanguageVersion.KOTLIN_1_0
+        }
+
+        m1.addDependency(m2)
+        m2.addDependency(m1)
+
+        checkHighlightingInAllFiles()
+    }
+
+    private fun Module.setupKotlinFacet(configure: KotlinFacetConfiguration.() -> Unit) = apply {
+        runWriteAction {
+            val facet = FacetManager.getInstance(this).addFacet(KotlinFacetType.INSTANCE, KotlinFacetType.NAME, null)
+            val configuration = facet.configuration
+
+            // this is actually needed so facet settings object is in a valid state
+            configuration.settings.compilerArguments = K2JVMCompilerArguments()
+            // make sure module-specific settings are used
+            configuration.settings.useProjectSettings = false
+
+            configuration.configure()
+        }
+    }
+
     class MultiPlatform : AbstractMultiModuleHighlightingTest() {
         override val testPath get() = super.testPath + "multiplatform/"