null argument checker: filter out unused parameters

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

@@ -18,6 +18,7 @@ package com.intellij.codeInspection.dataFlow;
 import com.intellij.codeInsight.NullableNotNullManager;
 import com.intellij.codeInspection.dataFlow.instructions.AssignInstruction;
 import com.intellij.codeInspection.dataFlow.instructions.Instruction;
+import com.intellij.codeInspection.dataFlow.instructions.PushInstruction;
 import com.intellij.codeInspection.dataFlow.instructions.ReturnInstruction;
 import com.intellij.codeInspection.dataFlow.value.DfaValue;
 import com.intellij.codeInspection.dataFlow.value.DfaValueFactory;
@@ -47,10 +48,12 @@ import java.util.Set;
  */
 class NullParameterConstraintChecker extends DataFlowRunner {
   private final Set<PsiParameter> myPossiblyViolatedParameters;
+  private final Set<PsiParameter> myUsedParameters;
 
   private NullParameterConstraintChecker(Collection<PsiParameter> parameters, boolean isOnTheFly) {
     super(false, true, isOnTheFly);
     myPossiblyViolatedParameters = new THashSet<>(parameters);
+    myUsedParameters = new THashSet<>();
   }
 
   @NotNull
@@ -73,7 +76,7 @@ class NullParameterConstraintChecker extends DataFlowRunner {
     final NullParameterConstraintChecker checker = new NullParameterConstraintChecker(nullableParameters, true);
     checker.analyzeMethod(method.getBody(), new StandardInstructionVisitor());
 
-    return checker.myPossiblyViolatedParameters.toArray(new PsiParameter[checker.myPossiblyViolatedParameters.size()]);
+    return checker.myPossiblyViolatedParameters.stream().filter(checker.myUsedParameters::contains).toArray(PsiParameter[]::new);
   }
 
   @NotNull
@@ -81,6 +84,16 @@ class NullParameterConstraintChecker extends DataFlowRunner {
   protected DfaInstructionState[] acceptInstruction(@NotNull InstructionVisitor visitor, @NotNull DfaInstructionState instructionState) {
     Instruction instruction = instructionState.getInstruction();
 
+    if (instruction instanceof PushInstruction) {
+      final DfaValue var = ((PushInstruction)instruction).getValue();
+      if (var instanceof DfaVariableValue) {
+        final PsiModifierListOwner psiVar = ((DfaVariableValue)var).getPsiVariable();
+        if (psiVar instanceof PsiParameter) {
+          myUsedParameters.add((PsiParameter)psiVar);
+        }
+      }
+    }
+
     if (instruction instanceof AssignInstruction) {
       final DfaValue value = ((AssignInstruction)instruction).getAssignedValue();
       if (value instanceof DfaVariableValue) {

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

@@ -0,0 +1,10 @@
+class Test {
+
+  void m() {
+    throwAnException(<warning descr="Passing 'null' argument to non annotated parameter">null</warning>);
+  }
+
+  static void throwAnException(String arg) {
+    throw new RuntimeException();
+  }
+}

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

@@ -405,4 +405,5 @@ public class DataFlowInspectionTest extends DataFlowInspectionTestCase {
   public void testNullLiteralAndInferredMethodContract() {
     doTest();
   }
+  public void testNullLiteralArgumentDoesntReportedWhenMethodOnlyThrowAnException() { doTest(); }
 }