declare is a special macro which can be used to add “meta”
properties to a function or macro: for example, marking it as
obsolete, or giving its forms a special <TAB> indentation
convention in Emacs Lisp mode.
This macro ignores its arguments and evaluates to
nil; it has no run-time effect. However, when a
declareform occurs in the declare argument of a
defsubstfunction definition (see Defining Functions) or a
defmacromacro definition (see Defining Macros), it appends the properties specified by specs to the function or macro. This work is specially performed by
Each element in specs should have the form
...), which should not be quoted. These have the following effects:
- This acts like a call to
set-advertised-calling-convention(see Obsolete Functions); signature specifies the correct argument list for calling the function or macro, and when should be a string indicating when the old argument list was first made obsolete.
- This is valid for macros only. When stepping through the macro with Edebug, use edebug-form-spec. See Instrumenting Macro Calls.
- This is used when defining a function or macro which itself will be used to define entities like functions, macros, or variables. It indicates that the nth argument, if any, should be considered as a documentation string.
- Indent calls to this function or macro according to indent-spec. This is typically used for macros, though it works for functions too. See Indenting Macros.
- Mark the function or macro as obsolete, similar to a call to
make-obsolete(see Obsolete Functions). current-name should be a symbol (in which case the warning message says to use that instead), a string (specifying the warning message), or
nil(in which case the warning message gives no extra details). when should be a string indicating when the function or macro was first made obsolete.
- This can only be used for functions, and tells the compiler to use expander as an optimization function. When encountering a call to the function, of the form
...), the macro expander will call expander with that form as well as with args..., and expander can either return a new expression to use instead of the function call, or it can return just the form unchanged, to indicate that the function call should be left alone. expander can be a symbol, or it can be a form
)in which case arg will hold the original function call expression, and the (unevaluated) arguments to the function can be accessed using the function's formal arguments.
- Declare expander to be the function to handle calls to the macro (or function) as a generalized variable, similarly to
gv-define-expander. expander can be a symbol or it can be of the form
)in which case that function will additionally have access to the macro (or function)'s arguments.
- Declare setter to be the function to handle calls to the macro (or function) as a generalized variable. setter can be a symbol in which case it will be passed to
gv-define-simple-setter, or it can be of the form
)in which case that function will additionally have access to the macro (or function)'s arguments and it will passed to