suggest to increase language level for unresolved var references

IDEA-188912

java/java-impl/src/com/intellij/codeInsight/daemon/impl/analysis/LocalVariableTypeInferenceUnresolvedFixProvider.java

@@ -0,0 +1,53 @@
+// 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.codeInsight.daemon.impl.analysis;
+
+import com.intellij.codeInsight.daemon.QuickFixActionRegistrar;
+import com.intellij.codeInsight.intention.QuickFixFactory;
+import com.intellij.codeInsight.quickfix.UnresolvedReferenceQuickFixProvider;
+import com.intellij.openapi.application.ApplicationManager;
+import com.intellij.pom.java.LanguageLevel;
+import com.intellij.psi.*;
+import com.intellij.psi.util.PsiUtil;
+import org.jetbrains.annotations.NotNull;
+
+public class LocalVariableTypeInferenceUnresolvedFixProvider extends UnresolvedReferenceQuickFixProvider<PsiJavaCodeReferenceElement> {
+  @Override
+  public void registerFixes(@NotNull PsiJavaCodeReferenceElement ref, @NotNull QuickFixActionRegistrar registrar) {
+    PsiElement typeElement = ref.getParent();
+    PsiElement parent = typeElement instanceof PsiTypeElement ? typeElement.getParent() : null;
+    boolean increaseLanguageLevel = true;
+    LanguageLevel targetLanguageLevel;
+    if (parent instanceof PsiParameter && ((PsiParameter)parent).getDeclarationScope() instanceof PsiLambdaExpression) {
+      //early-draft specification support to be enabled after release
+      if (LanguageLevel.HIGHEST.isAtLeast(LanguageLevel.JDK_X)) {
+        targetLanguageLevel = LanguageLevel.JDK_X;
+      }
+      else if (ApplicationManager.getApplication().isEAP()) {
+        targetLanguageLevel = LanguageLevel.JDK_X;
+
+        //show module options with ability to explicitly agree with legal notice
+        increaseLanguageLevel = false;
+      }
+      else {
+        return;
+      }
+    }
+    else {
+      targetLanguageLevel = LanguageLevel.JDK_10;
+    }
+
+    if (PsiUtil.getLanguageLevel(ref).isAtLeast(targetLanguageLevel)) return;
+    if (!PsiKeyword.VAR.equals(ref.getReferenceName())) return;
+
+    if (increaseLanguageLevel) {
+      registrar.register(QuickFixFactory.getInstance().createIncreaseLanguageLevelFix(targetLanguageLevel));
+    }
+    registrar.register(QuickFixFactory.getInstance().createShowModulePropertiesFix(ref));
+  }
+
+  @NotNull
+  @Override
+  public Class<PsiJavaCodeReferenceElement> getReferenceClass() {
+    return PsiJavaCodeReferenceElement.class;
+  }
+}

plugins/InspectionGadgets/src/META-INF/InspectionGadgets.xml

@@ -2798,6 +2798,7 @@
                      bundle="com.siyeh.InspectionGadgetsBundle" key="inspection.constant.expression.display.name"
                      groupBundle="messages.InspectionsBundle" groupKey="group.names.code.style.issues"
                      implementationClass="com.siyeh.ig.style.ConstantExpressionInspection"/>
+    <codeInsight.unresolvedReferenceQuickFixProvider implementation="com.intellij.codeInsight.daemon.impl.analysis.LocalVariableTypeInferenceUnresolvedFixProvider"/>
   </extensions>
 
 </idea-plugin>