[Ecls-list] Type propagator and "bogus" existing code

Juan Jose Garcia-Ripoll juanjose.garciaripoll at googlemail.com
Sat Jun 19 13:46:31 UTC 2010

I am greatly amazed at the improvements in type propagation -- which still
can not be called liked that, but which does some minimal type inference --,
probably because the stupid algorithm catches quite many problems already.

However, precisely due to the simplicity of the current algorithms, one
thing that may be a showstopper is that there is code around that looks like
   (when (stringp foo)
      (replace foo faa ...))

I am a bit lost here. On the one hand this is valid Lisp, even if FOO is
inferred to have, say, an integer type. However the compiler will see that
REPLACE gets arguments of the wrong type and will complain.

In a sense what the developer is asking from us here is that we not only
obey the type declarations but also ignore the unreachable code and probably
also keep branch-specific type information, which is too much asking for the
little infrastructure that is built right now.

- Emit an error as we did so far. Maxima and other programs will refuse to
- Emit a warning. Software having this problem built with ASDF will not
build because of the warnings.
- Emit a style-warning.
- Emit a compiler note.
- Somebody implements the remaining pieces in the compiler :-)

Which alternative do you feel more comfortable with?


Instituto de Física Fundamental, CSIC
c/ Serrano, 113b, Madrid 28006 (Spain)
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