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bug#19670: 24.4; pcase-let bug?

From: Stefan Monnier
Subject: bug#19670: 24.4; pcase-let bug?
Date: Mon, 26 Jan 2015 17:59:09 -0500
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/25.0.50 (gnu/linux)

> It seems to make more sense for pcase-let to signal an error or bind X
> to nil. WDYT?

Signaling an error would be fine.  But it significantly increases the
macro-expanded code size (i.e. it's a lot less efficient).
Defaulting to binding all vars to nil in case of match failure seems
like an even more surprising behavior than what we have now.

The current pcase-let (and pcase-dolist) is meant as a "destructuring"
operation: it doesn't *check* anything, it just accesses subelements of
a structure.


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