Chapter 8  Language extensions

This chapter describes language extensions and convenience features that are implemented in OCaml, but not described in the OCaml reference manual.

9  Overriding in open statements

(Introduced in OCaml 4.01)

definition::= ...  
 ∣  open! module-path  
 
specification::= ...  
 ∣  open! module-path  
 
expr::= ...  
 ∣ let open! module-path in  expr  
 
class-body-type::= ...  
 ∣  let open! module-path in  class-body-type  
 
class-expr::= ...  
 ∣  let open! module-path in  class-expr  
 

Since OCaml 4.01, open statements shadowing an existing identifier (which is later used) trigger the warning 44. Adding a ! character after the open keyword indicates that such a shadowing is intentional and should not trigger the warning.

This is also available (since OCaml 4.06) for local opens in class expressions and class type expressions.

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