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Reporting errors at macro-expansion time
Date: Tue, 12 Jul 88 16:53 EDT
From: DLA@jasper.scrc.symbolics.com (David L. Andre)
Date: Mon, 11 Jul 88 22:27 EDT
From: barmar@Think.COM (Barry Margolin)
Date: Mon, 11 Jul 88 13:34 EDT
From: email@example.com (Chris Lindblad)
What I do is use warn instead of error, and have the macro expand to something
safe, like nil.
NIL isn't safe. Expand into (PROGN) or (VALUES) instead. If the form
is in the body of a TAGBODY (or anything with an implicit tag body, such
as DO or PROG), NIL is treated as a tag, not a form, and if you have
multiple of them you will get a warning about duplicate tags.
Sorry. I was unaware that the body of a LET was an implicit tagbody.
The body of a LET is not an implicit tagbody. But who says that
macros are only used in the bodies of LET? Consider
If MY-MACRO expands into NIL, you get
nil (go foo))
which has duplicate NIL tags.