anonym -> lambda: expression lambda should be used with care due to void/value ambiguity (IDEA-125951)

java/java-analysis-impl/src/com/intellij/codeInspection/AnonymousCanBeLambdaInspection.java

@@ -211,8 +211,11 @@ public class AnonymousCanBeLambdaInspection extends BaseJavaBatchLocalInspection
       if (element instanceof PsiNewExpression) {
         if (!FileModificationService.getInstance().preparePsiElementForWrite(element)) return;
         final PsiAnonymousClass anonymousClass = ((PsiNewExpression)element).getAnonymousClass();
-        
+
         LOG.assertTrue(anonymousClass != null);
+
+        final boolean voidCompatible = PsiType.VOID.equals(LambdaUtil.getFunctionalInterfaceReturnType(anonymousClass.getBaseClassType()));
+
         ChangeContextUtil.encodeContextInfo(anonymousClass, true);
         final PsiElement lambdaContext = anonymousClass.getParent().getParent();
         boolean validContext = LambdaUtil.isValidLambdaContext(lambdaContext);
@@ -254,7 +257,7 @@ public class AnonymousCanBeLambdaInspection extends BaseJavaBatchLocalInspection
             if (value != null) {
               copy = value.copy();
             }
-          } else if (statements[0] instanceof PsiExpressionStatement) {
+          } else if (statements[0] instanceof PsiExpressionStatement && !(voidCompatible && lambdaContext instanceof PsiExpressionList)) {
             copy = ((PsiExpressionStatement)statements[0]).getExpression().copy();
           }
         }

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/anonymous2lambda/afterValueVoidCompatibleAmbiguity.java

@@ -0,0 +1,27 @@
+// "Replace with lambda" "true"
+import java.util.HashSet;
+import java.util.Set;
+
+class Test {
+  public static void main(String[] args) {
+    Set<String> strings = new HashSet<>();
+    new Test().query((ResultSet var1) -> strings.add("Col1"));
+  }
+
+  public void query(RowCallbackHandler rch){
+    System.out.println();
+  }
+
+  public Object query( final ResultSetExtractor rse) {
+    return null;
+  }
+}
+
+interface RowCallbackHandler {
+  void processRow(ResultSet var1);
+}
+
+interface ResultSetExtractor {
+  Object extractData(ResultSet var1);
+}
+class ResultSet {}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/anonymous2lambda/afterVoidValueCompatibleAmbiguity.java

@@ -0,0 +1,29 @@
+// "Replace with lambda" "true"
+import java.util.HashSet;
+import java.util.Set;
+
+class Test {
+  public static void main(String[] args) {
+    Set<String> strings = new HashSet<>();
+    new Test().query(pResultSet -> {
+      strings.add("Col1");
+    });
+  }
+
+  public void query(RowCallbackHandler rch){
+    System.out.println();
+  }
+
+  public Object query( final ResultSetExtractor rse) {
+    return null;
+  }
+}
+
+interface RowCallbackHandler {
+  void processRow(ResultSet var1);
+}
+
+interface ResultSetExtractor {
+  Object extractData(ResultSet var1);
+}
+class ResultSet {}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/anonymous2lambda/beforeValueVoidCompatibleAmbiguity.java

@@ -0,0 +1,32 @@
+// "Replace with lambda" "true"
+import java.util.HashSet;
+import java.util.Set;
+
+class Test {
+  public static void main(String[] args) {
+    Set<String> strings = new HashSet<>();
+    new Test().query(new Res<caret>ultSetExtractor() {
+      @Override
+      public Object extractData(ResultSet var1) {
+        return strings.add("Col1");
+      }
+    });
+  }
+
+  public void query(RowCallbackHandler rch){
+    System.out.println();
+  }
+
+  public Object query( final ResultSetExtractor rse) {
+    return null;
+  }
+}
+
+interface RowCallbackHandler {
+  void processRow(ResultSet var1);
+}
+
+interface ResultSetExtractor {
+  Object extractData(ResultSet var1);
+}
+class ResultSet {}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/anonymous2lambda/beforeVoidValueCompatibleAmbiguity.java

@@ -0,0 +1,32 @@
+// "Replace with lambda" "true"
+import java.util.HashSet;
+import java.util.Set;
+
+class Test {
+  public static void main(String[] args) {
+    Set<String> strings = new HashSet<>();
+    new Test().query(new RowCa<caret>llbackHandler() {
+      @Override
+      public void processRow(ResultSet pResultSet) {
+        strings.add("Col1");
+      }
+    });
+  }
+
+  public void query(RowCallbackHandler rch){
+    System.out.println();
+  }
+
+  public Object query( final ResultSetExtractor rse) {
+    return null;
+  }
+}
+
+interface RowCallbackHandler {
+  void processRow(ResultSet var1);
+}
+
+interface ResultSetExtractor {
+  Object extractData(ResultSet var1);
+}
+class ResultSet {}