[PATCH v3 7/8] qapi/error: Add type hints

[John Snow <jsnow@redhat.com>]

No functional change.

Note: QAPISourceError's info parameter is Optional[] because schema.py
treats the info property of its various classes as Optional to
accommodate built-in types, which have no source. See prior commit
'qapi/error: assert QAPISourceInfo is not None'.

Signed-off-by: John Snow <jsnow@redhat.com>

---

Random aside: It may appear clunky to have to type __str__, but after I
mentioned it on the Python typing SIG list, it was noted that this is
actually one of very few magic methods that has a "known" type in
advance, so there wasn't much desire to special case the typing for it.

Signed-off-by: John Snow <jsnow@redhat.com>
---
 scripts/qapi/error.py | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/scripts/qapi/error.py b/scripts/qapi/error.py
index 6723c5a9d9a..e35e4ddb26a 100644
--- a/scripts/qapi/error.py
+++ b/scripts/qapi/error.py
@@ -17,6 +17,10 @@
 parser.py.
 """
 
+from typing import Optional
+
+from .source import QAPISourceInfo
+
 
 class QAPIError(Exception):
     """Base class for all exceptions from the QAPI package."""
@@ -24,13 +28,16 @@ class QAPIError(Exception):
 
 class QAPISourceError(QAPIError):
     """Error class for all exceptions identifying a source location."""
-    def __init__(self, info, msg, col=None):
+    def __init__(self,
+                 info: Optional[QAPISourceInfo],
+                 msg: str,
+                 col: Optional[int] = None):
         super().__init__()
         self.info = info
         self.msg = msg
         self.col = col
 
-    def __str__(self):
+    def __str__(self) -> str:
         assert self.info is not None
         loc = str(self.info)
         if self.col is not None:
-- 
2.30.2