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qapi/expr.py: Add casts in a few select cases

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Casts are instructions to the type checker only, they aren't "safe" and
should probably be avoided in general. In this case, when we perform
type checking on a nested structure, the type of each field does not
"stick".

(See PEP 647 for an example of "type narrowing" that does "stick".
 It is available in Python 3.10, so we can't use it yet.)

We don't need to assert that something is a str if we've already checked
or asserted that it is -- use a cast instead for these cases.

Signed-off-by: John Snow <jsnow@redhat.com>
Message-Id: <20210421182032.3521476-9-jsnow@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
This commit is contained in:
John Snow 2021-04-21 14:20:23 -04:00 committed by Markus Armbruster
parent 4918bb7def
commit 7a783ce5b5
1 changed files with 5 additions and 5 deletions
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10
scripts/qapi/expr.py
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@ -15,7 +15,7 @@
# See the COPYING file in the top-level directory.
import re
from typing import Dict, Optional
from typing import Dict, Optional, cast
from .common import c_name
from .error import QAPISemError
@ -261,7 +261,7 @@ def check_enum(expr, info):
def check_struct(expr, info):
name = expr['struct']
name = cast(str, expr['struct']) # Checked in check_exprs
members = expr['data']
check_type(members, info, "'data'", allow_dict=name)
@ -269,7 +269,7 @@ def check_struct(expr, info):
def check_union(expr, info):
name = expr['union']
name = cast(str, expr['union']) # Checked in check_exprs
base = expr.get('base')
discriminator = expr.get('discriminator')
members = expr['data']
@ -368,8 +368,8 @@ def check_exprs(exprs):
else:
raise QAPISemError(info, "expression is missing metatype")
name = expr[meta]
check_name_is_str(name, info, "'%s'" % meta)
check_name_is_str(expr[meta], info, "'%s'" % meta)
name = cast(str, expr[meta])
info.set_defn(meta, name)
check_defn_name_str(name, info, meta)