IDEA-123301 Show a warning if 'List<@Nullable X>' is passed to a place where 'List<@NotNull X'> is expected

java/java-analysis-impl/src/com/intellij/codeInspection/nullable/NullableStuffInspectionBase.java

@@ -25,6 +25,7 @@ import com.intellij.codeInsight.intention.impl.AddNotNullAnnotationFix;
 import com.intellij.codeInspection.*;
 import com.intellij.codeInspection.dataFlow.DfaPsiUtil;
 import com.intellij.codeInspection.dataFlow.Nullness;
+import com.intellij.codeInspection.dataFlow.instructions.MethodCallInstruction;
 import com.intellij.openapi.diagnostic.Logger;
 import com.intellij.openapi.project.Project;
 import com.intellij.openapi.util.WriteExternalException;
@@ -158,6 +159,51 @@ public class NullableStuffInspectionBase extends BaseJavaBatchLocalInspectionToo
         }
         return false;
       }
+
+      @Override
+      public void visitAssignmentExpression(PsiAssignmentExpression expression) {
+        checkCollectionNullityOnAssignment(expression.getOperationSign(), expression.getLExpression().getType(), expression.getRExpression());
+      }
+
+      @Override
+      public void visitLocalVariable(PsiLocalVariable variable) {
+        PsiIdentifier identifier = variable.getNameIdentifier();
+        if (identifier != null) {
+          checkCollectionNullityOnAssignment(identifier, variable.getType(), variable.getInitializer());
+        }
+      }
+
+      @Override
+      public void visitCallExpression(PsiCallExpression callExpression) {
+        PsiExpressionList argList = callExpression.getArgumentList();
+        JavaResolveResult result = callExpression.resolveMethodGenerics();
+        PsiMethod method = (PsiMethod)result.getElement();
+        if (method == null || argList == null) return;
+
+        PsiSubstitutor substitutor = result.getSubstitutor();
+        PsiParameter[] parameters = method.getParameterList().getParameters();
+        PsiExpression[] arguments = argList.getExpressions();
+        for (int i = 0; i < arguments.length; i++) {
+          PsiExpression argument = arguments[i];
+          if (i < parameters.length &&
+              (i < parameters.length - 1 || !MethodCallInstruction.isVarArgCall(method, substitutor, arguments, parameters))) {
+            checkCollectionNullityOnAssignment(argument, substitutor.substitute(parameters[i].getType()), argument);
+          }
+        }
+      }
+
+      private void checkCollectionNullityOnAssignment(@NotNull PsiElement errorElement, PsiType expectedType, PsiExpression assignedExpression) {
+        PsiType lItemType = JavaGenericsUtil.getCollectionItemType(expectedType, errorElement.getResolveScope());
+        PsiType rItemType = assignedExpression == null ? null : JavaGenericsUtil.getCollectionItemType(assignedExpression);
+
+        if (DfaPsiUtil.getTypeNullability(lItemType) == Nullness.NOT_NULL &&
+            DfaPsiUtil.getTypeNullability(rItemType) == Nullness.NULLABLE) {
+          holder.registerProblem(errorElement,
+                                 "Assigning a collection of nullable elements into a collection of non-null elements",
+                                 ProblemHighlightType.GENERIC_ERROR_OR_WARNING);
+
+        }
+      }
     };
   }
 

java/java-tests/testData/inspection/nullableProblems/PassingNullableCollectionWhereNotNullIsExpected.java

@@ -0,0 +1,21 @@
+import typeUse.*;
+import java.util.*;
+
+class JC {
+
+  public static void main(String[] args) {
+    List<@Nullable String> list = new ArrayList<>();
+    print(<warning descr="Assigning a collection of nullable elements into a collection of non-null elements">list</warning>);
+
+    List<@NotNull String> <warning descr="Assigning a collection of nullable elements into a collection of non-null elements">list2</warning> = list;
+
+    List<@NotNull String> list3;
+    list2 <warning descr="Assigning a collection of nullable elements into a collection of non-null elements">=</warning> list;
+  }
+
+  private static void print(List<@NotNull String> list) {
+    for (String s : list) {
+      System.out.println(s.length());
+    }
+  }
+}

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

@@ -207,4 +207,9 @@ public class NullableStuffInspectionTest extends LightCodeInsightFixtureTestCase
     doTest();
   }
 
+  public void testPassingNullableCollectionWhereNotNullIsExpected() {
+    DataFlowInspection8Test.setupTypeUseAnnotations("typeUse", myFixture);
+    doTest();
+  }
+
 }