In some languages, however, data constructors live in a separate namespace from variables and in some they do not. In ML and Rust, mistyping a a data construct

In some languages, however, data constructors live in a separate namespace from variables and in some they do not. In ML and Rust, mistyping a a data constructor's name produces a variable, and thus matches everything, whereas OCaml and Haskell require that constructors start with an uppercase name, and disallows variables to do so, so this cannot easily occur. But, since in Rust data constructors are typically qualified with a namespace except for some frequently used ones, this is not a problem in practice.