Span-level controls are recognized after the initial set of Rho inline
elements, just before the generic `emitNormal` method.
function(walk) {
        if (this.emitText(walk)) return;
        if (this.tryInputText(walk)) return;
        if (this.tryInputRegex(walk)) return;
        if (this.tryInputTextWithDefault(walk)) return;
        if (this.trySelectMenu(walk)) return;
        var _super = InlineCompiler.prototype.emitNormal.bind(this);
        return _super(walk);
      }