Add examples for await-outside-async and fix activation of message

ChangeLog

@@ -26,6 +26,7 @@ Release date: TBA
 
   Closes #1555
 
+* Fix bug where specifically enabling just ``await-outside-async`` was not possible.
 
 ..
   Insert your changelog randomly, it will reduce merge conflicts

doc/data/messages/a/await-outside-async/bad.py

@@ -0,0 +1,5 @@
+import asyncio
+
+
+def main():
+    await asyncio.sleep(1)  # [await-outside-async]

doc/data/messages/a/await-outside-async/good.py

@@ -0,0 +1,5 @@
+import asyncio
+
+
+async def main():
+    await asyncio.sleep(1)

doc/data/messages/a/await-outside-async/related.rst

@@ -0,0 +1 @@
+- `PEP 492 <https://peps.python.org/pep-0492/#await-expression>`_

pylint/checkers/typecheck.py

@@ -1953,6 +1953,20 @@ def visit_for(self, node: nodes.For) -> None:
 
         self.add_message("dict-iter-missing-items", node=node)
 
+    @check_messages("await-outside-async")
+    def visit_await(self, node: nodes.Await) -> None:
+        self._check_await_outside_coroutine(node)
+
+    def _check_await_outside_coroutine(self, node: nodes.Await) -> None:
+        node_scope = node.scope()
+        while not isinstance(node_scope, nodes.Module):
+            if isinstance(node_scope, nodes.AsyncFunctionDef):
+                return
+            if isinstance(node_scope, nodes.FunctionDef):
+                break
+            node_scope = node_scope.parent.scope()
+        self.add_message("await-outside-async", node=node)
+
 
 class IterableChecker(BaseChecker):
     """Checks for non-iterables used in an iterable context.
@@ -2064,20 +2078,6 @@ def visit_generatorexp(self, node: nodes.GeneratorExp) -> None:
         for gen in node.generators:
             self._check_iterable(gen.iter, check_async=gen.is_async)
 
-    @check_messages("await-outside-async")
-    def visit_await(self, node: nodes.Await) -> None:
-        self._check_await_outside_coroutine(node)
-
-    def _check_await_outside_coroutine(self, node: nodes.Await) -> None:
-        node_scope = node.scope()
-        while not isinstance(node_scope, nodes.Module):
-            if isinstance(node_scope, nodes.AsyncFunctionDef):
-                return
-            if isinstance(node_scope, nodes.FunctionDef):
-                break
-            node_scope = node_scope.parent.scope()
-        self.add_message("await-outside-async", node=node)
-
 
 def register(linter: "PyLinter") -> None:
     linter.register_checker(TypeChecker(linter))