The major change in this patch is to add a new type of 'WordValue'
which is always used to represent finite sequences of bits. A word
value is either a packed word, or a sequence of lazy bits. The 'VSeq'
constructor, in constrast, is now never used for a finite sequence of
bits.
This avoids certain thorny problems that arise when trying to faithfully
implement the lazy semantics of Cryptol. We now do not have to commit
to a value at type '[n]' being represented as a packed word or as an
unpacked word until relatively late. This allows us to perform type-directed
eta-expansion at every recursive call before we know how words will be represented.
This patch fixes all the outstanding strictness bugs that I know of.
Unfortunately, we seem to lose some ground on performance. The new evaluator
is now about 5% slower than the old one on the AES benchmark, and quite a bit
slower on the SHA1 benchmark. Fortunately, the use if LRU caches for memoization
of sequences seems to keep heap usage to manageable levels; so programs generally
complete, even if they take a long time.
Cryptol.Eval.Type now provides three evaluation functions
for types:
evalType :: EvalEnv -> Type -> Either Nat' TValue
evalValType :: EvalEnv -> Type -> TValue
evalNumType :: EvalEnv -> Type -> Nat'
evalValType requires the type to have kind *.
evalNumType requires the type to have kind #.
evalType works on a Cryptol types of either kind.
This mostly takes care of issue #343, but some problems
remain:
- There is no TValue representation for newtypes
- Many incomplete pattern warnings in Symbolic/Prims.hs
* The MultipleSyms error should only show up when the import environment
contains duplicate symbols, and should be triggered lazily.
* Environments that have had errors reported should be rewritten to no longer
produce those errors during renameVar/renameType
Fixes#337
The local type bindings from type annotations in patterns were not being
processed correctly, and built-in type/type-functions were getting shadowed in
binders.
