[PATCH v3 10/20] qapi: use schema.resolve_type instead of schema.lookup_type

[John Snow <jsnow@redhat.com>]

the function lookup_type() is capable of returning None, but some
callers aren't prepared for that and assume it will always succeed. For
static type analysis purposes, this creates problems at those callsites.

Modify resolve_type() - which already cannot ever return None - to allow
'info' and 'what' parameters to be elided, which infers that the type
lookup is a built-in type lookup.

Change several callsites to use the new form of resolve_type to avoid
the more laborious strictly-typed error-checking scaffolding:

  ret = lookup_type("foo")
  assert ret is not None
  typ: QAPISchemaType = ret

which can be replaced with the simpler:

  typ = resolve_type("foo")

Signed-off-by: John Snow <jsnow@redhat.com>
---
 scripts/qapi/introspect.py | 4 ++--
 scripts/qapi/schema.py     | 5 ++---
 2 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/scripts/qapi/introspect.py b/scripts/qapi/introspect.py
index 67c7d89aae0..c38df61a6d5 100644
--- a/scripts/qapi/introspect.py
+++ b/scripts/qapi/introspect.py
@@ -227,10 +227,10 @@ def _use_type(self, typ: QAPISchemaType) -> str:
 
         # Map the various integer types to plain int
         if typ.json_type() == 'int':
-            typ = self._schema.lookup_type('int')
+            typ = self._schema.resolve_type('int')
         elif (isinstance(typ, QAPISchemaArrayType) and
               typ.element_type.json_type() == 'int'):
-            typ = self._schema.lookup_type('intList')
+            typ = self._schema.resolve_type('intList')
         # Add type to work queue if new
         if typ not in self._used_types:
             self._used_types.append(typ)
diff --git a/scripts/qapi/schema.py b/scripts/qapi/schema.py
index 573be7275a6..074897ee4fb 100644
--- a/scripts/qapi/schema.py
+++ b/scripts/qapi/schema.py
@@ -650,8 +650,7 @@ def check(self, schema, seen):
                     "discriminator '%s' is not a member of %s"
                     % (self._tag_name, base))
             # Here we do:
-            base_type = schema.lookup_type(self.tag_member.defined_in)
-            assert base_type
+            base_type = schema.resolve_type(self.tag_member.defined_in)
             if not base_type.is_implicit():
                 base = "base type '%s'" % self.tag_member.defined_in
             if not isinstance(self.tag_member.type, QAPISchemaEnumType):
@@ -1001,7 +1000,7 @@ def lookup_type(self, name):
         assert typ is None or isinstance(typ, QAPISchemaType)
         return typ
 
-    def resolve_type(self, name, info, what):
+    def resolve_type(self, name, info=None, what=None):
         typ = self.lookup_type(name)
         if not typ:
             assert info and what  # built-in types must not fail lookup
-- 
2.43.0