sb-simple-streams:open silently ignores unknown stream class

[Kambiz Darabi]

Calling open with a non-existent or non-stream :class argument

(sb-simple-streams:open "/etc/hosts" :class 'class-which-does-not-exist)

returns NIL without any error.

I have attached a patch which changes the cond form in open to signal
an error in that case. Two test cases are included.

This is the thread on the sbcl-devel mailing list:

http://sf.net/mailarchive/message.php?msg_id=28629268

I'm using SBCL 1.0.53.39 on Ubuntu Oneiric

Linux 3.0.0-12-generic #20-Ubuntu SMP Fri Oct 7 14:50:42 UTC 2011 i686 i686 i386 GNU/Linux

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 :IEEE-FLOATING-POINT :X86 :UNIX :ELF :LINUX :SB-THREAD :SB-FUTEX :LARGEFILE :GENCGC :STACK-GROWS-DOWNWARD-NOT-UPWARD :C-STACK-IS-CONTROL-STACK
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[Nikodemus Siivola (nikodemus)]

commit ac28b4bc430e89db490c9bb23ec7aa8d7cfe318a
Author: Kambiz Darabi <email address hidden>
Date: Fri Jan 6 09:11:36 2012 +0100

    sb-simple-streams: signal an error for bad stream classes in OPEN

      Instead of silently returning NIL, signal an error if the class does not
      exist (if argument :class is a symbol) or is not a stream class.

      lp#969352