From 1ad36b0e7aed48f237a9a411053e2135e415f15f Mon Sep 17 00:00:00 2001
From: Tagir Valeev <tagir.valeev@jetbrains.com>
Date: Tue, 25 Feb 2025 18:26:16 +0100
Subject: [PATCH] [java-dfa] IDEA-365459 "Treat non-annotated members and
 parameters as @Nullable" inspections makes constructors @Nullable

GitOrigin-RevId: b4c0234154171b658451e9628fd1bbc873e4699f
---
 .../java/inst/MethodReferenceInstruction.java | 15 +++++++++-
 .../NewMethodReferenceMustBeNonNull.java      | 28 +++++++++++++++++++
 .../DataFlowInspection8Test.java              |  3 ++
 3 files changed, 45 insertions(+), 1 deletion(-)
 create mode 100644 java/java-tests/testData/inspection/dataFlow/fixture/NewMethodReferenceMustBeNonNull.java

diff --git a/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/java/inst/MethodReferenceInstruction.java b/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/java/inst/MethodReferenceInstruction.java
index cb8d53f21fb5..fe6512b06c9a 100644
--- a/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/java/inst/MethodReferenceInstruction.java
+++ b/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/java/inst/MethodReferenceInstruction.java
@@ -10,6 +10,8 @@ import com.intellij.codeInspection.dataFlow.java.anchor.JavaMethodReferenceRetur
 import com.intellij.codeInspection.dataFlow.lang.ir.DfaInstructionState;
 import com.intellij.codeInspection.dataFlow.lang.ir.ExpressionPushingInstruction;
 import com.intellij.codeInspection.dataFlow.memory.DfaMemoryState;
+import com.intellij.codeInspection.dataFlow.types.DfType;
+import com.intellij.codeInspection.dataFlow.types.DfTypes;
 import com.intellij.codeInspection.dataFlow.value.DfaValue;
 import com.intellij.psi.*;
 import com.intellij.psi.util.TypeConversionUtil;
@@ -63,7 +65,18 @@ public class MethodReferenceInstruction extends ExpressionPushingInstruction {
     }
     List<? extends MethodContract> contracts = JavaMethodContractUtil.getMethodCallContracts(method, null);
     PsiType returnType = substitutor.substitute(method.getReturnType());
-    DfaValue defaultResult = interpreter.getFactory().fromDfType(typedObject(returnType, DfaPsiUtil.getElementNullability(returnType, method)));
+    DfType dfType;
+    if (method.isConstructor()) {
+      PsiClass containingClass = method.getContainingClass();
+      if (containingClass != null) {
+        dfType = TypeConstraints.exactClass(containingClass).asDfType().meet(DfTypes.NOT_NULL_OBJECT);
+      } else {
+        dfType = DfTypes.NOT_NULL_OBJECT;
+      }
+    } else {
+      dfType = typedObject(returnType, DfaPsiUtil.getElementNullability(returnType, method));
+    }
+    DfaValue defaultResult = interpreter.getFactory().fromDfType(dfType);
     Nullability expectedNullability = DfaPsiUtil.getTypeNullability(LambdaUtil.getFunctionalInterfaceReturnType(methodRef));
     if (expectedNullability == Nullability.NOT_NULL) {
       CheckNotNullInstruction.checkNotNullable(interpreter, state, defaultResult, 
diff --git a/java/java-tests/testData/inspection/dataFlow/fixture/NewMethodReferenceMustBeNonNull.java b/java/java-tests/testData/inspection/dataFlow/fixture/NewMethodReferenceMustBeNonNull.java
new file mode 100644
index 000000000000..db738d9e5b2e
--- /dev/null
+++ b/java/java-tests/testData/inspection/dataFlow/fixture/NewMethodReferenceMustBeNonNull.java
@@ -0,0 +1,28 @@
+import org.jetbrains.annotations.NotNull;
+import java.util.function.Function;
+import java.util.function.Supplier;
+
+class Main {
+  public static void main(String[] args) {
+    System.out.println("Hello, World!");
+
+    useConstructorAsFunction(InnerClass::new);
+    useConstructorAsSupplier(InnerClass::new);
+  }
+
+  public static void useConstructorAsFunction(@NotNull Function<@NotNull String, @NotNull InnerClass> function) {
+
+  }
+
+  public static void useConstructorAsSupplier(@NotNull Supplier<@NotNull InnerClass> supplier) {
+
+  }
+
+  public static class InnerClass {
+    public InnerClass(@NotNull String name) {
+    }
+
+    public InnerClass() {
+    }
+  }
+}
\ No newline at end of file
diff --git a/java/java-tests/testSrc/com/intellij/java/codeInspection/DataFlowInspection8Test.java b/java/java-tests/testSrc/com/intellij/java/codeInspection/DataFlowInspection8Test.java
index 4e1fc870fa29..b022e0f4ab6d 100644
--- a/java/java-tests/testSrc/com/intellij/java/codeInspection/DataFlowInspection8Test.java
+++ b/java/java-tests/testSrc/com/intellij/java/codeInspection/DataFlowInspection8Test.java
@@ -381,4 +381,7 @@ public class DataFlowInspection8Test extends DataFlowInspectionTestCase {
     doTest();
   }
   public void testFieldWriteInLambda() { doTest(); }
+  public void testNewMethodReferenceMustBeNonNull() {
+    doTestWith((insp, __) -> insp.TREAT_UNKNOWN_MEMBERS_AS_NULLABLE = true); 
+  }
 }
\ No newline at end of file