code: function warnTemplateSelectorNotFound (decl, result) {
    let rule = decl.parent
    let root = decl.root()
    let duplicatesFound = false
  
    // slice selector array. Remove the last part (for comparison)
    let slicedSelectorArr = list
      .space(rule.selector)
      .filter(str => str !== '>')
      .slice(0, -1)
  
    // we need to compare only if selector is complex.
    // e.g '.grid-cell' is simple, but '.parent > .grid-cell' is complex
    if (slicedSelectorArr.length > 0) {
      let gridTemplateFound = false
      let foundAreaSelector = null
  
      root.walkDecls(/grid-template(-areas)?$/, d => {
        let parent = d.parent
        let templateSelectors = parent.selectors
  
        let { areas } = parseTemplate({ decl: d, gap: getGridGap(d) })
        let hasArea = areas[decl.value]
  
        // find the the matching selectors
        for (let tplSelector of templateSelectors) {
          if (gridTemplateFound) {
            break
          }
          let tplSelectorArr = list
            .space(tplSelector)
            .filter(str => str !== '>')
  
          gridTemplateFound = tplSelectorArr.every(
            (item, idx) => item === slicedSelectorArr[idx]
          )
        }
  
        if (gridTemplateFound || !hasArea) {
          return true
        }
  
        if (!foundAreaSelector) {
          foundAreaSelector = parent.selector
        }
  
        // if we found the duplicate area with different selector
        if (foundAreaSelector && foundAreaSelector !== parent.selector) {
          duplicatesFound = true
        }
  
        return undefined
      })
  
      // warn user if we didn't find template
      if (!gridTemplateFound && duplicatesFound) {
        decl.warn(
          result,
          `Autoprefixer cannot find a grid-template ` +
          `containing the duplicate grid-area "${ decl.value }" ` +
          `with full selector matching: ${ slicedSelectorArr.join(' ') }`
        )
      }
    }
  }
docs: compare selectors with grid-area rule and grid-template rule
  show warning if grid-template selector is not found
  (this function used for grid-area rule)
  @param  {Declaration} decl
  @param  {Result} result
  @return {void}