null types (IDEA-146740)

java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/InferenceVariable.java

@@ -72,6 +72,11 @@ public class InferenceVariable extends LightTypeParameter {
       list = new ArrayList<PsiType>();
       myBounds.put(inferenceBound, list);
     }
+
+    if (classType == null) {
+      classType = PsiType.NULL;
+    }
+
     final int idx = list.indexOf(classType);
     if (idx < 0) {
       list.add(classType);

java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/TypeEqualityConstraint.java

@@ -72,8 +72,8 @@ public class TypeEqualityConstraint implements ConstraintFormula {
     }
 
     if (session.isProperType(myT) && session.isProperType(myS)) {
-      if (myT == null) return myS == null || myS.equalsToText(CommonClassNames.JAVA_LANG_OBJECT);
-      if (myS == null) return true;
+      if (myT == null || myT == PsiType.NULL) return myS == null || myS == PsiType.NULL || myS.equalsToText(CommonClassNames.JAVA_LANG_OBJECT);
+      if (myS == null || myS == PsiType.NULL) return true;
       return Comparing.equal(myT, myS);
     }
     InferenceVariable inferenceVariable = session.getInferenceVariable(myS);

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/lambda/diamond/NullTypesInDiamondsInference.java

@@ -0,0 +1,14 @@
+
+import java.util.List;
+import java.util.Set;
+
+class Test {
+  void foo(List<Set<String>> dictSeqs) {
+    final Dict<String> dict = new Dict<>(dictSeqs.toArray(new Set[dictSeqs.size()]));
+    final Dict<String> dict1 = new Dict<String>(dictSeqs.toArray(new Set[dictSeqs.size()]));
+  }
+
+  static class Dict<K extends Comparable<K>> {
+    public Dict(final Set<K>... sex) {}
+  }
+}

java/java-tests/testSrc/com/intellij/codeInsight/daemon/lambda/Diamond8HighlightingTest.java

@@ -55,6 +55,10 @@ public class Diamond8HighlightingTest extends LightDaemonAnalyzerTestCase {
     doTest();
   }
 
+  public void testNullTypesInDiamondsInference() throws Exception {
+    doTest();
+  }
+
   private void doTest() throws Exception {
     doTest(BASE_PATH + "/" + getTestName(false) + ".java", false, false);
   }