parser: add a check for known vars in or block (#7094)

vlib/v/parser/parser.v

@@ -645,7 +645,7 @@ pub fn (mut p Parser) stmt(is_top_level bool) ast.Stmt {
 				} else if p.peek_tok.kind == .name {
 					p.error_with_pos('unexpected name `$p.peek_tok.lit`', p.peek_tok.position())
 				} else if !p.inside_if_expr && !p.inside_match_body && !p.inside_or_expr &&
-					p.peek_tok.kind in [.rcbr, .eof] {
+					p.peek_tok.kind in [.rcbr, .eof] && !p.mark_var_as_used(p.tok.lit) {
 					p.error_with_pos('`$p.tok.lit` evaluated but not used', p.tok.position())
 				}
 			}

vlib/v/tests/option_default_values_test.v

@@ -154,3 +154,13 @@ fn test_nested_optional_with_opt_fn_call_as_last_value() {
 	// }
 	// assert e == false
 }
+
+fn remove_suffix1(s string) string {
+    n := s.len
+    i := s.last_index('.') or { n }
+    return s[0..i]
+}
+
+fn test_var_inside_or_block() {
+	assert remove_suffix1('Vlang.foo') == 'Vlang'
+}