qapi: Move duplicate collision checks to schema check()

With the recent commit 'qapi: Detect collisions in C member
names', we have two different locations for detecting clashes -
one at parse time, and another at QAPISchema*.check() time.
Remove all of the ad hoc parser checks, and delete associated
code (for example, the global check_member_clash() method is
no longer needed).

Testing this showed that the test union-bad-branch wasn't adding
much: union-clash-branches also exposes the error message when
branches collide, and we've recently fixed things to avoid an
implicit collision with max. Likewise, the error for
enum-clash-member changes to report our new detection of
upper case in a value name, unless we modify the test to use
all lower case.

The wording of several error messages has changed, but the
change is generally an improvement rather than a regression.

No change to generated code.

Backports commit 01cfbaa4c36ecd9f1c7bcbad50c92758e1d147c4 from qemu

qemu/scripts/qapi.py

@@ -521,21 +521,6 @@ def check_type(expr_info, source, value, allow_array=False,
                                 'enum'])
 
 
-def check_member_clash(expr_info, base_name, data, source=""):
-    base = find_struct(base_name)
-    assert base
-    base_members = base['data']
-    for key in data.keys():
-        if key.startswith('*'):
-            key = key[1:]
-        if key in base_members or "*" + key in base_members:
-            raise QAPIExprError(expr_info,
-                                "Member name '%s'%s clashes with base '%s'"
-                                % (key, source, base_name))
-    if base.get('base'):
-        check_member_clash(expr_info, base['base'], data, source)
-
-
 def check_command(expr, expr_info):
     name = expr['command']
 
@@ -565,7 +550,6 @@ def check_union(expr, expr_info):
     base = expr.get('base')
     discriminator = expr.get('discriminator')
     members = expr['data']
-    values = {}
 
     # Two types of unions, determined by discriminator.
 
@@ -612,15 +596,9 @@ def check_union(expr, expr_info):
     for (key, value) in members.items():
         check_name(expr_info, "Member of union '%s'" % name, key)
 
-        # Each value must name a known type; furthermore, in flat unions,
-        # branches must be a struct with no overlapping member names
+        # Each value must name a known type
         check_type(expr_info, "Member '%s' of union '%s'" % (key, name),
                    value, allow_array=not base, allow_metas=allow_metas)
-        if base:
-            branch_struct = find_struct(value)
-            assert branch_struct
-            check_member_clash(expr_info, base, branch_struct['data'],
-                               " of branch '%s'" % key)
 
         # If the discriminator names an enum type, then all members
         # of 'data' must also be members of the enum type.
@@ -631,34 +609,16 @@ def check_union(expr, expr_info):
                                     "enum '%s'" %
                                     (key, enum_define["enum_name"]))
 
-        # Otherwise, check for conflicts in the generated enum
-        else:
-            c_key = camel_to_upper(key)
-            if c_key in values:
-                raise QAPIExprError(expr_info,
-                                    "Union '%s' member '%s' clashes with '%s'"
-                                    % (name, key, values[c_key]))
-            values[c_key] = key
-
 
 def check_alternate(expr, expr_info):
     name = expr['alternate']
     members = expr['data']
-    values = {}
     types_seen = {}
 
     # Check every branch
     for (key, value) in members.items():
         check_name(expr_info, "Member of alternate '%s'" % name, key)
 
-        # Check for conflicts in the branch names
-        c_key = c_name(key)
-        if c_key in values:
-            raise QAPIExprError(expr_info,
-                                "Alternate '%s' member '%s' clashes with '%s'"
-                                % (name, key, values[c_key]))
-        values[c_key] = key
-
         # Ensure alternates have no type conflicts.
         check_type(expr_info, "Member '%s' of alternate '%s'" % (key, name),
                    value,
@@ -677,7 +637,6 @@ def check_enum(expr, expr_info):
     name = expr['enum']
     members = expr.get('data')
     prefix = expr.get('prefix')
-    values = {}
 
     if not isinstance(members, list):
         raise QAPIExprError(expr_info,
@@ -688,12 +647,6 @@ def check_enum(expr, expr_info):
     for member in members:
         check_name(expr_info, "Member of enum '%s'" % name, member,
                    enum_member=True)
-        key = camel_to_upper(member)
-        if key in values:
-            raise QAPIExprError(expr_info,
-                                "Enum '%s' member '%s' clashes with '%s'"
-                                % (name, member, values[key]))
-        values[key] = member
 
 
 def check_struct(expr, expr_info):
@@ -704,8 +657,6 @@ def check_struct(expr, expr_info):
                allow_dict=True, allow_optional=True)
     check_type(expr_info, "'base' for struct '%s'" % name, expr.get('base'),
                allow_metas=['struct'])
-    if expr.get('base'):
-        check_member_clash(expr_info, expr['base'], expr['data'])
 
 
 def check_keys(expr_elem, meta, required, optional=[]):