code: function() {
      var tok = this.advance();
      var tag = {
        type: 'InterpolatedTag',
        expr: tok.val,
        selfClosing: false,
        block: this.emptyBlock(tok.line),
        attrs: [],
        attributeBlocks: [],
        isInline: false,
        line: tok.line,
        filename: this.filename
      };
  
      return this.tag(tag, {selfClosingAllowed: true});
    }
docs: interpolation (attrs | class | id)* (text | code | ':')? newline* block?