Berry var allowed in with walrus operator := (arendst#19018)

* Berry `var` allowed in with walrus operator `:=`

* fix regression

CHANGELOG.md

@@ -9,6 +9,7 @@ All notable changes to this project will be documented in this file.
 - Matter add option to disable bridge mode (#18992)
 - Support for SGP41 TVOC/NOx Sensor (#18880)
 - Command ``BrRestart`` to restart the Berry VM (experimental)
+- Berry `var` allowed in with walrus operator `:=`
 
 ### Breaking Changed
 - Berry `bool( [] )` and `bool( {} )` now evaluate as `false` (#18986)

lib/libesp32/berry/src/be_parser.c

@@ -1135,8 +1135,22 @@ static void sub_expr(bparser *parser, bexpdesc *e, int prio)
 static void walrus_expr(bparser *parser, bexpdesc *e)
 {
     int line = parser->lexer.linenumber;
-    sub_expr(parser, e, ASSIGN_OP_PRIO);    /* left expression */
     btokentype op = next_type(parser);
+    if (op == KeyVar) {
+        /* 'var' ID ':=' expr */
+        scan_next_token(parser); /* skip 'var' */
+        bstring *name;
+        name = next_token(parser).u.s;
+        match_token(parser, TokenId); /* match and skip ID */
+        new_var(parser, name, e); /* new variable */         
+        op = next_type(parser);
+        if (op != OptWalrus) {
+            parser_error(parser, "'var' in expr must be followed by ':='");
+        }
+    } else {
+        sub_expr(parser, e, ASSIGN_OP_PRIO);    /* left expression */
+        op = next_type(parser);
+    }
     if (op == OptWalrus) {
         check_symbol(parser, e);
         bexpdesc e1 = *e;           /* copy var to e1, e will get the result of expression */
@@ -1149,8 +1163,7 @@ static void walrus_expr(bparser *parser, bexpdesc *e)
         }
         if (be_code_setvar(parser->finfo, &e1, e, btrue /* do not release register */ )) {
             parser->lexer.linenumber = line;
-            parser_error(parser,
-                "try to assign constant expressions.");
+            parser_error(parser, "try to assign constant expressions.");
         }
     }
 }