Always treat all sources as parts of the module being compiled

If a path to the module-info.java file is passed as an argument, we
should treat all other source files passed as arguments (either as
individual source files or inside a source directory) as members of that
module. Previously we treated other source files as members of the
unnamed module, and this resulted in incorrect errors when using a
member exported with a qualification from another named module, for
example

 #KT-18598 In Fixed

compiler/tests/org/jetbrains/kotlin/jvm/compiler/Java9ModulesIntegrationTest.kt

@@ -54,12 +54,14 @@ class Java9ModulesIntegrationTest : AbstractKotlinCompilerIntegrationTest() {
                     }
                     KotlinTestUtils.compileJavaFilesExternallyWithJava9(javaFiles, javaOptions)
                 },
-                checkKotlinOutput = { actual ->
-                    KotlinTestUtils.assertEqualsToFile(File(testDataDirectory, "$name.txt"), actual)
-                }
+                checkKotlinOutput = checkKotlinOutput(name)
         )
     }
 
+    private fun checkKotlinOutput(moduleName: String): (String) -> Unit = { actual ->
+        KotlinTestUtils.assertEqualsToFile(File(testDataDirectory, "$moduleName.txt"), actual)
+    }
+
     fun testSimple() {
         val a = module("moduleA")
         module("moduleB", listOf(a))
@@ -130,4 +132,21 @@ class Java9ModulesIntegrationTest : AbstractKotlinCompilerIntegrationTest() {
         val c = module("moduleC", listOf(a, b))
         module("moduleD", listOf(c, b, a))
     }
+
+    fun testSpecifyPathToModuleInfoInArguments() {
+        val a = module("moduleA")
+
+        val jdk9Home = KotlinTestUtils.getJdk9HomeIfPossible() ?: return
+        val kotlinOptions = mutableListOf(
+                "$testDataDirectory/someOtherDirectoryWithTheActualModuleInfo/module-info.java",
+                "-jdk-home", jdk9Home.path,
+                "-Xmodule-path=${a.path}"
+        )
+        compileLibrary(
+                "moduleB",
+                additionalOptions = kotlinOptions,
+                compileJava = { _, _, _ -> error("No .java files in moduleB in this test") },
+                checkKotlinOutput = checkKotlinOutput("moduleB")
+        )
+    }
 }