Fix version brackets in CHOICE

Quote from Rec. ITU-T X.691 (02/2021) end of section 23:
"NOTE – Version brackets in the definition of choice extension
additions have no effect on how "ExtensionAdditionAlternatives"
are encoded."

In other words elements inside version brackets should not be grouped
together for CHOICE (as opposed to how its done for SEQUENCE).

libasn1compiler/asn1c_C.c

@@ -973,7 +973,6 @@ asn1c_lang_C_type_CHOICE(arg_t *arg) {
 	asn1p_expr_t *expr = arg->expr;
 	asn1p_expr_t *v;
 	int saved_target = arg->target->target;
-	int ext_num = 1;
 
 	DEPENDENCIES;
 
@@ -994,13 +993,6 @@ asn1c_lang_C_type_CHOICE(arg_t *arg) {
 				continue;
 			}
 
-			if((v->expr_type == ASN_CONSTR_SEQUENCE) &&
-				(v->marker.flags & EM_OPTIONAL) &&
-				(v->Identifier == NULL)) {
-				char ext_name[20];
-				sprintf(ext_name, "ext%d", ext_num++);
-				v->Identifier = strdup(ext_name);
-			}
 			OUT("%s", c_presence_name(arg, v));
 		}
 		OUT("\n");

libasn1parser/asn1p_y.y

@@ -1097,10 +1097,8 @@ AlternativeTypeLists:
 	}
 	| AlternativeTypeLists ',' TOK_VBracketLeft AlternativeTypeLists TOK_VBracketRight {
 		$$ = $1;
-		$4->meta_type = AMT_TYPE;
-		$4->expr_type = ASN_CONSTR_SEQUENCE;
-		$4->marker.flags |= EM_OPTIONAL;
-		asn1p_expr_add($$, $4);
+		asn1p_expr_add_many($$, $4);
+		asn1p_expr_free($4);
 	}
 	;
 

tests/tests-asn1c-compiler/165-choice-extended-group-OK.asn1

@@ -0,0 +1,31 @@
+
+-- OK: Everything is fine
+
+-- iso.org.dod.internet.private.enterprise (1.3.6.1.4.1)
+-- .spelio.software.asn1c.test (9363.1.5.1)
+-- .165
+
+ModuleTestExtensibleChoice
+	{ iso org(3) dod(6) internet(1) private(4) enterprise(1)
+		spelio(9363) software(1) asn1c(5) test(1) 165 }
+	DEFINITIONS AUTOMATIC TAGS ::=
+BEGIN
+
+	Choice ::= CHOICE {
+		a	INTEGER,
+		...,
+		b	INTEGER,
+		[[
+		c	INTEGER
+		]],
+		[[
+		d	INTEGER,
+		e	INTEGER
+		]],
+		[[
+		f	INTEGER,
+		g	INTEGER
+		]]
+	}
+
+END