widget binding: Properly escape widget names at definition.

Re-Fixes zsh-users/zsh-syntax-highlighting#278.

zsh-syntax-highlighting.zsh

@@ -224,19 +224,22 @@ _zsh_highlight_bind_widgets()
 
       # The "eval"'s are required to make $cur_widget a closure: the value of the parameter at function
       # definition time is used.
+      #
+      # We can't use ${0/_zsh_highlight_widget_} because these widgets are always invoked with
+      # NO_function_argzero, regardless of the option's setting here.
 
       # User defined widget: override and rebind old one with prefix "orig-".
       user:*) zle -N orig-$cur_widget ${widgets[$cur_widget]#*:}
-              eval "_zsh_highlight_widget_$cur_widget() { _zsh_highlight_call_widget orig-$cur_widget -- \"\$@\" }"
+              eval "_zsh_highlight_widget_${(q)cur_widget}() { _zsh_highlight_call_widget orig-${(q)cur_widget} -- \"\$@\" }"
               zle -N $cur_widget _zsh_highlight_widget_$cur_widget;;
 
       # Completion widget: override and rebind old one with prefix "orig-".
       completion:*) zle -C orig-$cur_widget ${${widgets[$cur_widget]#*:}/:/ }
-                    eval "_zsh_highlight_widget_$cur_widget() { _zsh_highlight_call_widget orig-$cur_widget -- \"\$@\" }"
+                    eval "_zsh_highlight_widget_${(q)cur_widget}() { _zsh_highlight_call_widget orig-${(q)cur_widget} -- \"\$@\" }"
                     zle -N $cur_widget _zsh_highlight_widget_$cur_widget;;
 
       # Builtin widget: override and make it call the builtin ".widget".
-      builtin) eval "_zsh_highlight_widget_$cur_widget() { _zsh_highlight_call_widget .$cur_widget -- \"\$@\" }"
+      builtin) eval "_zsh_highlight_widget_${(q)cur_widget}() { _zsh_highlight_call_widget .${(q)cur_widget} -- \"\$@\" }"
                zle -N $cur_widget _zsh_highlight_widget_$cur_widget;;
 
       # Default: unhandled case.