ShowExpressionTypeAction: extension point & providers

java/java-impl/src/com/intellij/codeInsight/hint/JavaTypeProvider.java

@@ -0,0 +1,51 @@
+/*
+ * Copyright 2000-2015 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.intellij.codeInsight.hint;
+
+import com.intellij.lang.ExpressionTypeProvider;
+import com.intellij.openapi.util.text.StringUtil;
+import com.intellij.psi.PsiElement;
+import com.intellij.psi.PsiExpression;
+import com.intellij.psi.PsiType;
+import com.intellij.psi.SyntaxTraverser;
+import org.jetbrains.annotations.NotNull;
+
+import java.util.List;
+
+/**
+ * @author gregsh
+ */
+public class JavaTypeProvider extends ExpressionTypeProvider<PsiExpression> {
+  @NotNull
+  @Override
+  public String getInformationHint(@NotNull PsiExpression element) {
+    PsiType type = element.getType();
+    String text = type == null ? "<unknown>" : type.getCanonicalText();
+    return StringUtil.escapeXml(text);
+  }
+
+  @NotNull
+  @Override
+  public String getErrorHint() {
+    return "No expression found";
+  }
+
+  @NotNull
+  @Override
+  public List<PsiExpression> getExpressionsAt(@NotNull PsiElement elementAt) {
+    return SyntaxTraverser.psiTraverser().parents(elementAt).filter(PsiExpression.class).toList();
+  }
+}