all the little dances required to have Find Usages working

idea/src/META-INF/plugin.xml

@@ -29,6 +29,7 @@
       <lang.psiStructureViewFactory language="jet" implementationClass="org.jetbrains.jet.plugin.structureView.JetStructureViewFactory"/>
       <lang.foldingBuilder language="jet" implementationClass="org.jetbrains.jet.plugin.JetFoldingBuilder"/>
       <lang.formatter language="jet" implementationClass="org.jetbrains.jet.plugin.formatter.JetFormattingModelBuilder"/>
+      <lang.findUsagesProvider language="jet" implementationClass="org.jetbrains.jet.plugin.findUsages.JetFindUsagesProvider"/>
       <annotator language="jet" implementationClass="org.jetbrains.jet.plugin.annotations.SoftKeywordsAnnotator"/>
       <annotator language="jet" implementationClass="org.jetbrains.jet.plugin.annotations.LabelsAnnotator"/>
       <annotator language="jet" implementationClass="org.jetbrains.jet.plugin.annotations.JetPsiChecker"/>
@@ -38,5 +39,6 @@
       <codeInsight.lineMarkerProvider language="jet" implementationClass="org.jetbrains.jet.plugin.annotations.JetLineMarkerProvider"/>
       <iconProvider implementation="org.jetbrains.jet.plugin.JetIconProvider"/>
       <fileTypeIndentOptionsProvider implementation="org.jetbrains.jet.plugin.formatter.JetIndentOptionsProvider"/>
+      <elementDescriptionProvider implementation="org.jetbrains.jet.plugin.findUsages.JetElementDescriptionProvider"/>
   </extensions>
 </idea-plugin>

idea/src/org/jetbrains/jet/plugin/findUsages/JetElementDescriptionProvider.java

+package org.jetbrains.jet.plugin.findUsages;
+
+import com.intellij.psi.ElementDescriptionLocation;
+import com.intellij.psi.ElementDescriptionProvider;
+import com.intellij.psi.PsiElement;
+import com.intellij.psi.PsiNamedElement;
+import com.intellij.usageView.UsageViewLongNameLocation;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.jet.lang.psi.JetElement;
+
+/**
+ * @author yole
+ */
+public class JetElementDescriptionProvider implements ElementDescriptionProvider {
+    @Override
+    public String getElementDescription(@NotNull PsiElement element, @NotNull ElementDescriptionLocation location) {
+        if (location instanceof UsageViewLongNameLocation) {
+          if (element instanceof PsiNamedElement && element instanceof JetElement) {
+            return ((PsiNamedElement)element).getName();
+          }
+        }
+        return null;
+    }
+}

idea/src/org/jetbrains/jet/plugin/findUsages/JetFindUsagesProvider.java

+package org.jetbrains.jet.plugin.findUsages;
+
+import com.intellij.lang.cacheBuilder.WordsScanner;
+import com.intellij.lang.findUsages.FindUsagesProvider;
+import com.intellij.psi.PsiElement;
+import com.intellij.psi.PsiNamedElement;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.jet.lang.psi.*;
+
+/**
+ * @author yole
+ */
+public class JetFindUsagesProvider implements FindUsagesProvider {
+    @Override
+    public boolean canFindUsagesFor(@NotNull PsiElement psiElement) {
+        return psiElement instanceof JetNamedDeclaration;
+    }
+
+    @Override
+    public WordsScanner getWordsScanner() {
+        return new JetWordsScanner();
+    }
+
+
+    @Override
+    public String getHelpId(@NotNull PsiElement psiElement) {
+        return null;
+    }
+
+    @NotNull
+    @Override
+    public String getType(@NotNull PsiElement psiElement) {
+        if (psiElement instanceof JetFunction) {
+            return "function";
+        }
+        if (psiElement instanceof JetClass) {
+            return "class";
+        }
+        if (psiElement instanceof JetParameter) {
+            return "parameter";
+        }
+        if (psiElement instanceof JetProperty) {
+            return "property";
+        }
+        return "";
+    }
+
+    @NotNull
+    @Override
+    public String getDescriptiveName(@NotNull PsiElement psiElement) {
+        if (psiElement instanceof PsiNamedElement) {
+          final String name = ((PsiNamedElement)psiElement).getName();
+          return name == null ? "<unnamed>" : name;
+        }
+        return "";
+    }
+
+    @NotNull
+    @Override
+    public String getNodeText(@NotNull PsiElement psiElement, boolean useFullName) {
+        return getDescriptiveName(psiElement);
+    }
+}

idea/src/org/jetbrains/jet/plugin/findUsages/JetWordsScanner.java

+package org.jetbrains.jet.plugin.findUsages;
+
+import com.intellij.lang.cacheBuilder.DefaultWordsScanner;
+import com.intellij.psi.tree.TokenSet;
+import org.jetbrains.jet.lexer.JetLexer;
+import org.jetbrains.jet.lexer.JetTokens;
+
+/**
+ * @author yole
+ */
+public class JetWordsScanner extends DefaultWordsScanner {
+    public JetWordsScanner() {
+        super(new JetLexer(),
+                TokenSet.create(JetTokens.IDENTIFIER),
+                JetTokens.COMMENTS,
+                JetTokens.STRINGS);
+    }
+}