Overriding a coroutine method does not add the "async" keyword (PY-19312)

python/src/com/jetbrains/python/codeInsight/override/PyOverrideImplementUtil.java

@@ -203,6 +203,9 @@ public class PyOverrideImplementUtil {
     if (anno != null && level.isAtLeast(LanguageLevel.PYTHON30)) {
       pyFunctionBuilder.annotation(anno.getText());
     }
+    if (baseFunction.isAsync()) {
+      pyFunctionBuilder.makeAsync();
+    }
     final TypeEvalContext context = TypeEvalContext.userInitiated(baseFunction.getProject(), baseFunction.getContainingFile());
     final List<PyCallableParameter> baseParams = baseFunction.getParameters(context);
     for (PyCallableParameter parameter : baseParams) {

python/testData/override/asyncMethod.py

@@ -0,0 +1,6 @@
+class A:
+    async def foo(self):
+        pass
+
+class B(A):
+    <caret>pass

python/testData/override/asyncMethod_after.py

@@ -0,0 +1,8 @@
+class A:
+    async def foo(self):
+        pass
+
+class B(A):
+    async def foo(self):
+        return super().foo()
+

python/testSrc/com/jetbrains/python/PyOverrideTest.java

@@ -188,4 +188,9 @@ public class PyOverrideTest extends PyTestCase {
     PyOverrideImplementUtil.overrideMethods(myFixture.getEditor(), cls, Collections.singletonList(new PyMethodMember(method)), false);
     myFixture.checkResultByFile("override/" + getTestName(true) + "_after.py", true);
   }
+
+  // PY-19312
+  public void testAsyncMethod() {
+    runWithLanguageLevel(LanguageLevel.PYTHON36, () -> doTest());
+  }
 }