xo-tokenizer: (clang 15) compiler nits

include/xo/tokenizer/span.hpp

@@ -71,7 +71,7 @@ namespace xo {
 
             /** @brief create span with first @p z members of this span removed **/
             span after_prefix(size_type z) const {
-                if (z > hi_ - lo_)
+                if (lo_ + z > hi_)
                     z = hi_ - lo_;
 
                 return span(lo_ + z, hi_);

include/xo/tokenizer/tokenizer.hpp

@@ -646,6 +646,8 @@ namespace xo {
             } else if (is_2char_punctuation(*ix)) {
                 CharT ch1 = *ix;
 
+                (void)ch1;
+
                 ++ix;
 
                 if (ix == input.hi()) {

utest/tokenizer.test.cpp

@@ -111,6 +111,8 @@ namespace xo {
                 {"let", false, token::let(), true},
                 {"in", false, token::in(), true},
                 {"end", false, token::end(), true},
+
+                {"*", false, token::star_token(), true},
             };
         }