if len(p.goBuild) > 0 && p.goBuild[0] < insert {
		insert = p.goBuild[0]
	} else if len(p.plusBuild) > 0 && p.plusBuild[0] < insert {
		insert = p.plusBuild[0]
	}

	var x constraint.Expr
	switch len(p.goBuild) {
	case 0:
		// Synthesize //go:build expression from // +build lines.
		for _, pos := range p.plusBuild {
			y, err := constraint.Parse(p.commentTextAt(pos))
			if err != nil {
				x = nil
				break
			}

			// Even so, report.
			check.pass.Reportf(pos, "%v", err)
			check.crossCheck = false
			return
		}
		if check.plusBuild == nil {
			check.plusBuild = y
		} else {
			check.plusBuild = &constraint.AndExpr{X: check.plusBuild, Y: y}
		}
	}
}

func (check *checker) finish() {
	if !check.crossCheck || check.plusBuildPos == token.NoPos || check.goBuildPos == token.NoPos {