Chapter 12 Language extensions

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.