Report nullable Map.get if map values are nullable

Part of IDEA-236740

GitOrigin-RevId: d507993271d302a7a5fb2e3d1aacb3274cea79b1

java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/DfaPsiUtil.java

@@ -104,7 +104,7 @@ public class DfaPsiUtil {
     }
 
     if (owner instanceof PsiMethod && isMapMethodWithUnknownNullity((PsiMethod)owner)) {
-      return Nullability.UNKNOWN;
+      return getTypeNullability(resultType) == Nullability.NULLABLE ? Nullability.NULLABLE : Nullability.UNKNOWN;
     }
 
     Nullability fromType = getTypeNullability(resultType);

java/java-tests/testData/inspection/dataFlow/fixture/MapGetWithValueNullability.java

@@ -8,6 +8,7 @@ class Test {
     if (value == null) {
       System.out.println("it's not contained");
     }
+    map.get("z").intValue();
 
     value = hashMap.get("y");
     if (value == null) {
@@ -15,6 +16,11 @@ class Test {
     }
   }
 
+  public void main1(Map<@NotNull String, @Nullable Integer> map, HashMap<@NotNull String, @Nullable Integer> hashMap) {
+    map.get("y").<warning descr="Method invocation 'intValue' may produce 'NullPointerException'">intValue</warning>();
+    hashMap.get("y").<warning descr="Method invocation 'intValue' may produce 'NullPointerException'">intValue</warning>();
+  }
+
   public void main2(Map<@NotNull String, @NotNull Integer> map, HashMap<@NotNull String, @NotNull Integer> hashMap) {
     Integer value = map.remove("y");
     if (value == null) {

java/java-tests/testSrc/com/intellij/java/codeInspection/DataFlowInspection8Test.java

@@ -197,7 +197,7 @@ public class DataFlowInspection8Test extends DataFlowInspectionTestCase {
   public void testStreamCustomSumMethod() { doTest(); }
   public void testStreamReduceLogicalAnd() { doTest(); }
   
-  public void testMapGetWithNotNullKeys() { doTestWithCustomAnnotations(); }
+  public void testMapGetWithValueNullability() { doTestWithCustomAnnotations(); }
   public void testInferNestedForeachNullability() { doTestWithCustomAnnotations(); }
 
   public void testMethodVsExpressionTypeAnnotationConflict() {