warn when accessing static method of interfaces in language levels prior to 1.8 (IDEA-134814)

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

@@ -347,8 +347,10 @@ public class HighlightMethodUtil {
       TextRange fixRange = getFixRange(methodCall);
       highlightInfo = HighlightUtil.checkUnhandledExceptions(methodCall, fixRange);
       if (highlightInfo == null) {
-        if (!LambdaUtil.isValidQualifier4InterfaceStaticMethodCall((PsiMethod)resolved, methodCall.getMethodExpression(), resolveResult.getCurrentFileResolveScope(), languageLevel)) {
-          highlightInfo = HighlightInfo.newHighlightInfo(HighlightInfoType.ERROR).descriptionAndTooltip("Static method may be invoked on containing interface class only").range(fixRange).create();
+        final String invalidCallMessage = 
+          LambdaUtil.getInvalidQualifier4StaticInterfaceMethodMessage((PsiMethod)resolved, methodCall.getMethodExpression(), resolveResult.getCurrentFileResolveScope(), languageLevel);
+        if (invalidCallMessage != null) {
+          highlightInfo = HighlightInfo.newHighlightInfo(HighlightInfoType.ERROR).descriptionAndTooltip(invalidCallMessage).range(fixRange).create();
         } else {
           highlightInfo = GenericsHighlightUtil.checkInferredIntersections(substitutor, fixRange);
         }

java/java-psi-api/src/com/intellij/psi/LambdaUtil.java

@@ -457,15 +457,28 @@ public class LambdaUtil {
   public static boolean isValidQualifier4InterfaceStaticMethodCall(@NotNull PsiMethod method,
                                                                    @NotNull PsiReferenceExpression methodReferenceExpression,
                                                                    @Nullable PsiElement scope, @NotNull LanguageLevel languageLevel) {
-    if (languageLevel.isAtLeast(LanguageLevel.JDK_1_8)) {
-      final PsiExpression qualifierExpression = methodReferenceExpression.getQualifierExpression();
-      final PsiClass containingClass = method.getContainingClass();
-      if (containingClass != null && containingClass.isInterface() && method.hasModifierProperty(PsiModifier.STATIC)) {
-        return qualifierExpression == null && (scope instanceof PsiImportStaticStatement || PsiTreeUtil.isAncestor(containingClass, methodReferenceExpression, true))||
-               qualifierExpression instanceof PsiReferenceExpression && ((PsiReferenceExpression)qualifierExpression).resolve() == containingClass;
+    return getInvalidQualifier4StaticInterfaceMethodMessage(method, methodReferenceExpression, scope, languageLevel) == null;
+  }
+
+  @Nullable
+  public static String getInvalidQualifier4StaticInterfaceMethodMessage(@NotNull PsiMethod method,
+                                                                        @NotNull PsiReferenceExpression methodReferenceExpression,
+                                                                        @Nullable PsiElement scope, @NotNull LanguageLevel languageLevel) {
+    final PsiExpression qualifierExpression = methodReferenceExpression.getQualifierExpression();
+    final PsiClass containingClass = method.getContainingClass();
+    if (containingClass != null && containingClass.isInterface() && method.hasModifierProperty(PsiModifier.STATIC)) {
+      if (!languageLevel.isAtLeast(LanguageLevel.JDK_1_8)) {
+        return "Static interface method invocations are not supported at this language level";
       }
+
+      if (qualifierExpression == null && 
+          (scope instanceof PsiImportStaticStatement || PsiTreeUtil.isAncestor(containingClass, methodReferenceExpression, true)) || 
+          qualifierExpression instanceof PsiReferenceExpression && ((PsiReferenceExpression)qualifierExpression).resolve() == containingClass) {
+        return null;
+      }
+      return "Static method may be invoked on containing interface class only";
     }
-    return true;
+    return null;
   }
 
   //JLS 14.8 Expression Statements

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/advHighlighting7/AccessToStaticMethodsFromInterfaces.java

@@ -0,0 +1,14 @@
+class Test {
+  interface I {
+    <error descr="Extension methods are not supported at this language level">static void foo() {}</error>
+  }
+  
+  abstract class IImpl implements I {}
+  interface I2 extends I {}
+
+  {
+    <error descr="Static interface method invocations are not supported at this language level">I.foo();</error>
+    <error descr="Static interface method invocations are not supported at this language level">IImpl.foo();</error>
+    <error descr="Static interface method invocations are not supported at this language level">I2.foo();</error>
+  }
+}

java/java-tests/testSrc/com/intellij/codeInsight/daemon/LightAdvHighlightingJdk7Test.java

@@ -187,4 +187,5 @@ public class LightAdvHighlightingJdk7Test extends LightDaemonAnalyzerTestCase {
   public void testIDEA111420() { doTest(false, false); }
   public void testIDEA111450() { doTest(true, false); }
   public void testExternalizable() { doTest(true, false); }
+  public void testAccessToStaticMethodsFromInterfaces() { doTest(true, false); }
 }