github.com/solo-io/cue@v0.4.7/doc/tutorial/basics/2_types/20_bottom.txt (about)

     1  cue eval -i bottom.cue
     2  cmp stdout expect-stdout-cue
     3  
     4  -- frontmatter.toml --
     5  title = "Bottom / Error"
     6  description = ""
     7  
     8  -- text.md --
     9  Specifying duplicate fields with conflicting values results in an error
    10  or bottom.
    11  _Bottom_ is a special value in CUE, denoted `_|_`, that indicates an
    12  error such as conflicting values.
    13  Any error in CUE results in `_|_`.
    14  Logically all errors are equal, although errors may be associated with
    15  metadata such as an error message.
    16  
    17  Note that an error is different from `null`: `null` is a valid value,
    18  whereas `_|_` is not.
    19  
    20  -- bottom.cue --
    21  a: 4
    22  a: 5
    23  
    24  l: [ 1, 2 ]
    25  l: [ 1, 3 ]
    26  
    27  list: [0, 1, 2]
    28  val: list[3]
    29  
    30  -- expect-stdout-cue --
    31  list: [0, 1, 2]
    32  a: _|_ // conflicting values 4 and 5
    33  l: [1, _|_, // conflicting values 2 and 3
    34  ]
    35  val: _|_ // index 3 out of bounds