JS backend: report diagonstic message for unsupported element instead of throw exception.

#KT-6507 Fixed

js/js.frontend/src/org/jetbrains/kotlin/js/resolve/diagnostics/DefaultErrorMessagesJs.kt

@@ -34,6 +34,8 @@ private val DIAGNOSTIC_FACTORY_TO_RENDERER by Delegates.lazy {
         put(ErrorsJs.JSCODE_ERROR, "JavaScript: {0}", JsCallDataTextRenderer)
         put(ErrorsJs.JSCODE_WARNING, "JavaScript: {0}", JsCallDataTextRenderer)
         put(ErrorsJs.JSCODE_ARGUMENT_SHOULD_BE_CONSTANT, "Argument must be string constant")
+        put(ErrorsJs.NOT_SUPPORTED, "Cannot translate (not supported yet): ''{0}''", RenderFirstLineOfElementText)
+
 
         this
     }

js/js.frontend/src/org/jetbrains/kotlin/js/resolve/diagnostics/ErrorsJs.java

@@ -39,6 +39,7 @@ public interface ErrorsJs {
     DiagnosticFactory1<JetExpression, JsCallData> JSCODE_ERROR = DiagnosticFactory1.create(ERROR, JsCodePositioningStrategy.INSTANCE$);
     DiagnosticFactory1<JetExpression, JsCallData> JSCODE_WARNING = DiagnosticFactory1.create(WARNING, JsCodePositioningStrategy.INSTANCE$);
     DiagnosticFactory0<JetExpression> JSCODE_ARGUMENT_SHOULD_BE_CONSTANT = DiagnosticFactory0.create(ERROR, DEFAULT);
+    DiagnosticFactory1<JetElement, JetElement> NOT_SUPPORTED = DiagnosticFactory1.create(ERROR, DEFAULT);
 
     @SuppressWarnings("UnusedDeclaration")
     Object _initializer = new Object() {

js/js.frontend/src/org/jetbrains/kotlin/js/resolve/diagnostics/jsRenderers.kt

@@ -16,10 +16,17 @@
 
 package org.jetbrains.kotlin.js.resolve.diagnostics
 
-import org.jetbrains.kotlin.renderer.Renderer
-import org.jetbrains.kotlin.js.resolve.diagnostics.JsCallData
-import org.jetbrains.kotlin.js.resolve.diagnostics.JsCallDataWithCode
 import com.google.gwt.dev.js.rhino.Utils.isEndOfLine
+import com.intellij.psi.PsiElement
+import org.jetbrains.kotlin.renderer.Renderer
+
+object RenderFirstLineOfElementText : Renderer<PsiElement> {
+    override fun render(element: PsiElement): String {
+        val text = element.getText()
+        val index = text.indexOf('\n')
+        return if (index == -1) text else text.substring(0, index) + "..."
+    }
+}
 
 abstract class JsCallDataRenderer : Renderer<JsCallData> {
     protected abstract fun format(data: JsCallDataWithCode): String