#124 hygenic renaming incorrect for implicit module import

[Andrew Wilcox]

The following

(module m (a b)
(module ((a x))
(define x 10)
(define (a) x))
(module ((b x))
(define x 20)
(define (b) x)))
(import m)
(display (a))

displays 10 in Petite Chez Scheme but 20 in SISC 1.9.6.

Looking at the output of sc-expand:

...
(#%begin
(#%set! |@m::x| 10)
(#%set! |@m::a| (#%lambda () |@m::x|))
(#%set! |@m::x| 20)
(#%set! |@m::b| (#%lambda () |@m::x|)))

I suspect that SISC's feature of naming module exports
with the name of the module ("@m::a") to support
independant compilation of modules is being incorrectly
applied in the case of implicit imports. Since the two
definitions of "x" are in separate syntactic scopes,
the identifier should be hygenically given different names.

Thank you,

Andrew

[Scott G. Miller]

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The difference is that Chez doesn't support independent
compilation, but we do. This is a bug, but it may not be
easily fixable. Is this occuring in real code?

[Andrew Wilcox]

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> Is this occuring in real code?

Yes, this bug causes my proposed reference implementation
for SRFI-65 (see
http://srfi.schemers.org/srfi-65/srfi-65.html\) to not work
in SISC.

However, I believe that for SISC a working implementation of
the SRFI can be made by constructing a unique identifier for
the normally hidden, but exported, "promise" variable.

[Scott G. Miller]

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Fixed in CVS. Hopefully this fix will be general enough to
cover all cases. Testing need to be sure.