PY-83047 False positive "This code is unreachable" after attribute assignment to None under an if

Merge-request: IJ-MR-173356
Merged-by: Aleksandr Govenko <aleksandr.govenko@jetbrains.com>

GitOrigin-RevId: 08669d49a831548c354096fbb5cbec1a155da4e2

python/testSrc/com/jetbrains/python/Py3ResolveTest.java

@@ -805,7 +805,7 @@ public class Py3ResolveTest extends PyResolveTestCase {
   public void testInstanceAttrOtherMethodAndAbove() {
     final PyTargetExpression target = assertResolvesTo(PyTargetExpression.class, "foo");
     final PyFunction function = assertInstanceOf(ScopeUtil.getScopeOwner(target), PyFunction.class);
-    assertEquals("f", function.getName());
+    assertEquals("g", function.getName());
   }
 
   public void testInstanceAttrBelowAndOtherMethodAbove() {

python/testSrc/com/jetbrains/python/Py3TypeTest.java

@@ -17,6 +17,108 @@ import java.util.Map;
 
 public class Py3TypeTest extends PyTestCase {
   public static final String TEST_DIRECTORY = "/types/";
+  
+  // See PyReferenceExpressionImpl.getQualifiedReferenceType for explanations.
+  public void testQualifiedNameResolution() {
+    doTest("str", """
+      class C:
+          def m(self):
+              self.t = 5
+      
+      def f(self: C, x: float):
+          self.t = "foo"
+          expr = self.t
+      """);
+
+    doTest("int", """
+      class C:
+          def m(self):
+              self.t: int = 5
+      
+      def f(self: C, x: float):
+          self.t = "foo"
+          expr = self.t
+      """);
+
+    doTest("int", """
+      class C:
+          def __init__(self):
+              self.t: int = 5
+      
+      def f(self: C, x: float):
+          self.t = "foo"
+          expr = self.t
+      """);
+  }
+  
+  // PY-83047
+  public void testQualifiedReferenceTypeNarrowing() {
+    doTest("int | None", """
+      class C:
+          def __init__(self):
+              self.t: int | None = 5
+      
+          def f(self, x: float):
+              if x < 0:
+                  self.t = None
+      
+              expr = self.t
+      """);
+
+    doTest("int", """
+      class C:
+          def __init__(self):
+              self.t: int | None = 5
+      
+          def f(self, x: float):
+              if self.t is not None:
+                  expr = self.t
+      """);
+
+    doTest("None", """
+      class C:
+          def __init__(self):
+              self.t: int | None = 5
+      
+          def f(self, x: float):
+              if self.t is None:
+                  expr = self.t
+      """);
+
+    // Same, but as a separate function
+    
+    doTest("int | None", """
+      class C:
+          def __init__(self):
+              self.t: int | None = 5
+      
+      def f(self: C, x: float):
+          if x < 0:
+              self.t = None
+  
+          expr = self.t
+      """);
+
+    doTest("int", """
+      class C:
+          def __init__(self):
+              self.t: int | None = 5
+      
+      def f(self: C, x: float):
+          if self.t is not None:
+              expr = self.t
+      """);
+
+    doTest("None", """
+      class C:
+          def __init__(self):
+              self.t: int | None = 5
+      
+      def f(self: C, x: float):
+          if self.t is None:
+              expr = self.t
+      """);
+  }
 
   /** 
   Overload signatures for dict.get and dict.pop in builtins.pyi differ slightly,

python/testSrc/com/jetbrains/python/inspections/PyFinalInspectionTest.java

@@ -353,7 +353,7 @@ public class PyFinalInspectionTest extends PyInspectionTestCase {
                                    self.a: Final[str] = "str"
 
                                def method(self):
-                                   <warning descr="'Final' attribute should be declared in class body or '__init__'">self.a</warning>: Final[int] = 10
+                                   <warning descr="'Final' attribute should be declared in class body or '__init__'"><warning descr="Already declared name could not be redefined as 'Final'">self.a</warning></warning>: Final[int] = 10
                                    <warning descr="'Final' attribute should be declared in class body or '__init__'">self.b</warning>: Final[int] = 10""")
     );
   }