PY-23057 Fixed: "Statement has no effect" inspection should ignore ellipsis operator

PyTypeCheckerInspection, PyStatementEffectInspection and PyUnusedLocalInspection consider `...` as `pass`.

python/src/com/jetbrains/python/inspections/PyStatementEffectInspection.java

@@ -157,6 +157,9 @@ public class PyStatementEffectInspection extends PyInspection {
         final PyPrefixExpression prefixExpr = (PyPrefixExpression)expression;
         return prefixExpr.getOperator() == PyTokenTypes.AWAIT_KEYWORD;
       }
+      else if (expression instanceof PyNoneLiteralExpression && ((PyNoneLiteralExpression)expression).isEllipsis()) {
+        return true;
+      }
       return false;
     }
   }

python/src/com/jetbrains/python/psi/PyUtil.java

@@ -1790,25 +1790,31 @@ public class PyUtil {
       return true;
     }
     else if (statements.length == 1) {
-      if (isStringLiteral(statements[0]) || isPassOrRaiseOrEmptyReturn(statements[0])) {
+      if (isStringLiteral(statements[0]) || isPassOrRaiseOrEmptyReturnOrEllipsis(statements[0])) {
         return true;
       }
     }
     else if (statements.length == 2) {
-      if (isStringLiteral(statements[0]) && (isPassOrRaiseOrEmptyReturn(statements[1]))) {
+      if (isStringLiteral(statements[0]) && (isPassOrRaiseOrEmptyReturnOrEllipsis(statements[1]))) {
         return true;
       }
     }
     return false;
   }
 
-  private static boolean isPassOrRaiseOrEmptyReturn(PyStatement stmt) {
+  private static boolean isPassOrRaiseOrEmptyReturnOrEllipsis(PyStatement stmt) {
     if (stmt instanceof PyPassStatement || stmt instanceof PyRaiseStatement) {
       return true;
     }
     if (stmt instanceof PyReturnStatement && ((PyReturnStatement)stmt).getExpression() == null) {
       return true;
     }
+    if (stmt instanceof PyExpressionStatement) {
+      final PyExpression expression = ((PyExpressionStatement)stmt).getExpression();
+      if (expression instanceof PyNoneLiteralExpression && ((PyNoneLiteralExpression)expression).isEllipsis()) {
+        return true;
+      }
+    }
     return false;
   }
 

python/testData/inspections/PyStatementEffectInspection/functionWithEllipsis.py

@@ -0,0 +1,2 @@
+def foo():
+    ...

python/testData/inspections/PyTypeCheckerInspection/EllipsisInFunctionWithSpecifiedReturnType.py

@@ -0,0 +1,2 @@
+def bar() -> int:
+    ...

python/testData/inspections/PyUnusedLocalInspection/parameterInMethodWithEllipsis.py

@@ -0,0 +1,3 @@
+class A:
+    def bar(self, p):
+        ...

python/testSrc/com/jetbrains/python/inspections/Py3TypeCheckerInspectionTest.java

@@ -32,7 +32,6 @@ public class Py3TypeCheckerInspectionTest extends PyTestCase {
 
   private void doTest() {
     runWithLanguageLevel(LanguageLevel.PYTHON36, () -> {
-      myFixture.copyDirectoryToProject("typing", "");
       myFixture.configureByFile(TEST_DIRECTORY + getTestName(false) + ".py");
       myFixture.enableInspections(PyTypeCheckerInspection.class);
       myFixture.checkHighlighting(true, false, true);
@@ -42,7 +41,6 @@ public class Py3TypeCheckerInspectionTest extends PyTestCase {
   private void doMultiFileTest() {
     runWithLanguageLevel(LanguageLevel.PYTHON36, () -> {
       myFixture.copyDirectoryToProject(TEST_DIRECTORY + getTestName(false), "");
-      myFixture.copyDirectoryToProject("typing", "");
       myFixture.configureFromTempProjectFile("a.py");
       myFixture.enableInspections(PyTypeCheckerInspection.class);
       myFixture.checkHighlighting(true, false, true);
@@ -237,4 +235,9 @@ public class Py3TypeCheckerInspectionTest extends PyTestCase {
   public void testTypingNamedTupleAsParameter() {
     doTest();
   }
+
+  // PY-23057
+  public void testEllipsisInFunctionWithSpecifiedReturnType() {
+    doTest();
+  }
 }

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

@@ -35,6 +35,11 @@ public class PyStatementEffectInspectionTest extends PyInspectionTestCase {
     doTest();
   }
 
+  // PY-23057
+  public void testFunctionWithEllipsis() {
+    doTest(LanguageLevel.PYTHON35);
+  }
+
   private void doTest(@NotNull LanguageLevel level) {
     runWithLanguageLevel(level, this::doTest);
   }

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

@@ -77,6 +77,11 @@ public class PyUnusedLocalInspectionTest extends PyTestCase {
     runWithLanguageLevel(LanguageLevel.PYTHON35, this::doTest);
   }
 
+  // PY-23057
+  public void testParameterInMethodWithEllipsis() {
+    runWithLanguageLevel(LanguageLevel.PYTHON35, this::doTest);
+  }
+
   private void doTest() {
     final String path = "inspections/PyUnusedLocalInspection/" + getTestName(true) + ".py";