JS: report error when js() produces empty AST

compiler/testData/diagnostics/testsWithJsStdLib/jsCode/noJavaScriptProduced.kt

@@ -0,0 +1,16 @@
+fun test() {
+    js(<!JSCODE_NO_JAVASCRIPT_PRODUCED!>""<!>)
+    js(<!JSCODE_NO_JAVASCRIPT_PRODUCED!>" "<!>)
+    js(<!JSCODE_NO_JAVASCRIPT_PRODUCED!>"""
+               """<!>)
+
+    val empty = ""
+    js(<!JSCODE_NO_JAVASCRIPT_PRODUCED!>empty<!>)
+
+    val whitespace = "  "
+    js(<!JSCODE_NO_JAVASCRIPT_PRODUCED!>whitespace<!>)
+
+    val multiline = """
+    """
+    js(<!JSCODE_NO_JAVASCRIPT_PRODUCED!>multiline<!>)
+}

compiler/testData/diagnostics/testsWithJsStdLib/jsCode/noJavaScriptProduced.txt

@@ -0,0 +1,3 @@
+package
+
+internal fun test(): kotlin.Unit

compiler/tests/org/jetbrains/kotlin/checkers/JetDiagnosticsTestWithJsStdLibGenerated.java

@@ -257,6 +257,12 @@ public class JetDiagnosticsTestWithJsStdLibGenerated extends AbstractJetDiagnost
             doTest(fileName);
         }
 
+        @TestMetadata("noJavaScriptProduced.kt")
+        public void testNoJavaScriptProduced() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/testsWithJsStdLib/jsCode/noJavaScriptProduced.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("warning.kt")
         public void testWarning() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/testsWithJsStdLib/jsCode/warning.kt");