Types and Values
Specifying duplicate fields with conflicting values results in an error, denoted _|_.
Technically speaking, bottom is just a value like any other. But for all practical purposes it is okay to think of the bottom value as an error.
Note that an error is different from null: null is a valid JSON value, whereas _|_ is not.
a: 4 a: 5 l: [ 1, 2 ] l: [ 1, 3 ]
a: _|_ l: _|_