CLHS: Issue SYMBOL-MACROLET-DECLARE Writeup

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## Issue SYMBOL-MACROLET-DECLARE Writeup

    Issue:         SYMBOL-MACROLET-DECLARE

    References:    SYMBOL-MACROLET (88-002R page 2-81)
                   WITH-ACCESSORS (88-002R page 2-88)
                   WITH-SLOTS (88-002R page 2-92)

    Related Issues: SYMBOL-MACROLET-SEMANTICS
                   FLET-DECLARATIONS (passed)

    Category:      ADDITION

    Edit history:  Version 1, 12-Sep-88, Moon
                   Version 2,  9-Dec-88, Masinter
                     (add cross reference, discussion)

    Problem description:

    It would be both natural and nice to be able to write

      (with-slots (rho theta) point
        (declare (single-float rho theta))
        ...computation...)

    Proposal (SYMBOL-MACROLET-DECLARE:ALLOW):

    Allow declarations at the head of the body of SYMBOL-MACROLET, and hence
    in WITH-ACCESSORS and WITH-SLOTS.  Exactly the same declarations are
    allowed as for LET, with one exception: SYMBOL-MACROLET signals an error
    if a SPECIAL declaration names one of the symbols being defined as a
    symbol-macrolet.  A type declaration of one of these symbols is equivalent
    to wrapping a THE expression around the expansion of that symbol.

    Example:

    See problem description.

    Rationale:

    If SYMBOL-MACROLET is intended to resemble LET in syntax, it ought to
    allow declarations.  When writing a SYMBOL-MACROLET directly, the user
    could just as easily write a THE expression instead of a type
    declaration.  However, when invoking a macro such as WITH-SLOTS that
    expands into SYMBOL-MACROLET, the user does not have this option since
    the expansion is not supplied explicitly by the user.

    Current practice:

    SYMBOL-MACROLET was only tentatively added to Common Lisp 3 months ago.

    Cost to Implementors:

    Less than one man-hour.

    Cost to Users:

    None.

    Cost of non-adoption:

    Minor wart in the language.

    Benefits:

    More consistent language definition.

    Esthetics:

    More consistent language definition.

    Discussion:

    This issue is related to SYMBOL-MACROLET-SEMANTICS.

    "A macro-definition for SYMBOL-MACROLET would leave the issue of
    DECLARE open.  But the special-form version of SYMBOL-MACROLET
    really should address it."

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