navigate from var in lambda parameter

java/java-psi-impl/src/com/intellij/psi/impl/source/PsiTypeElementImpl.java

@@ -163,6 +163,11 @@ public class PsiTypeElementImpl extends CompositePsiElement implements PsiTypeEl
         if (iteratedValue != null) {
           return JavaGenericsUtil.getCollectionItemType(iteratedValue);
         }
+        return null;
+      }
+
+      if (declarationScope instanceof PsiLambdaExpression) {
+        return ((PsiParameter)parent).getType();
       }
     }
     else {

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/advHighlighting11/GotoDeclarationOnLambdaVarParameter.java

@@ -0,0 +1,7 @@
+import java.util.function.Function;
+
+class Main {
+    public static void main(String[] args) {
+        Function<String, String> f = (final v<caret>ar a) -> a;
+    }
+}

java/java-tests/testSrc/com/intellij/java/codeInsight/daemon/LightAdvHighlightingJdk11Test.java

@@ -0,0 +1,39 @@
+// Copyright 2000-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+package com.intellij.java.codeInsight.daemon;
+
+import com.intellij.codeInsight.daemon.LightDaemonAnalyzerTestCase;
+import com.intellij.codeInsight.navigation.actions.GotoDeclarationAction;
+import com.intellij.openapi.projectRoots.JavaSdkVersion;
+import com.intellij.openapi.projectRoots.Sdk;
+import com.intellij.pom.java.LanguageLevel;
+import com.intellij.psi.CommonClassNames;
+import com.intellij.psi.PsiClass;
+import com.intellij.psi.PsiElement;
+import com.intellij.testFramework.IdeaTestUtil;
+
+public class LightAdvHighlightingJdk11Test extends LightDaemonAnalyzerTestCase {
+  private static final String BASE_PATH = "/codeInsight/daemonCodeAnalyzer/advHighlighting11";
+
+  @Override
+  protected void setUp() throws Exception {
+    super.setUp();
+    setLanguageLevel(LanguageLevel.JDK_X);
+    IdeaTestUtil.setTestVersion(JavaSdkVersion.JDK_10, getModule(), getTestRootDisposable());//todo
+  }
+
+  public void testGotoDeclarationOnLambdaVarParameter() {
+    configureByFile(BASE_PATH + "/" + getTestName(false) + ".java");
+    final int offset = getEditor().getCaretModel().getOffset();
+    final PsiElement[] elements =
+      GotoDeclarationAction.findAllTargetElements(getProject(), getEditor(), offset);
+    assertSize(1, elements);
+    PsiElement element = elements[0];
+    assertInstanceOf(element, PsiClass.class);
+    assertEquals(CommonClassNames.JAVA_LANG_STRING, ((PsiClass)element).getQualifiedName());
+  }
+
+  @Override
+  protected Sdk getProjectJDK() {
+    return IdeaTestUtil.getMockJdk9();
+  }
+}