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(.module:
lux
(lux (control [monad #+ do]
["ex" exception #+ exception:])
(data [maybe]
[text]
text/format
(coll [list "list/" Functor<List>]))
[macro "macro/" Monad<Meta>]
(lang [type]
(type ["tc" check])))
(luxc ["&" lang]
(lang ["la" analysis #+ Analysis]
(analysis ["&." common]))))
(exception: #export Cannot-Infer)
(def: (cannot-infer type args)
(-> Type (List Code) Text)
(format " Type: " (%type type) "\n"
"Arguments:"
(|> args
list.enumerate
(list/map (function [[idx argC]]
(format "\n " (%n idx) " " (%code argC))))
(text.join-with ""))))
(exception: #export Cannot-Infer-Argument)
(exception: #export Smaller-Variant-Than-Expected)
(exception: #export Invalid-Type-Application)
(exception: #export Not-A-Record-Type)
(exception: #export Not-A-Variant-Type)
(def: (replace-bound bound-idx replacementT type)
(-> Nat Type Type Type)
(case type
(#.Primitive name params)
(#.Primitive name (list/map (replace-bound bound-idx replacementT) params))
(^template [<tag>]
(<tag> left right)
(<tag> (replace-bound bound-idx replacementT left)
(replace-bound bound-idx replacementT right)))
([#.Sum]
[#.Product]
[#.Function]
[#.Apply])
(#.Bound idx)
(if (n/= bound-idx idx)
replacementT
type)
(^template [<tag>]
(<tag> env quantified)
(<tag> (list/map (replace-bound bound-idx replacementT) env)
(replace-bound (n/+ +2 bound-idx) replacementT quantified)))
([#.UnivQ]
[#.ExQ])
_
type))
## Type-inference works by applying some (potentially quantified) type
## to a sequence of values.
## Function types are used for this, although inference is not always
## done for function application (alternative uses may be records and
## tagged variants).
## But, so long as the type being used for the inference can be treated
## as a function type, this method of inference should work.
(def: #export (general analyse inferT args)
(-> &.Analyser Type (List Code) (Meta [Type (List Analysis)]))
(case args
#.Nil
(do macro.Monad<Meta>
[_ (&.infer inferT)]
(wrap [inferT (list)]))
(#.Cons argC args')
(case inferT
(#.Named name unnamedT)
(general analyse unnamedT args)
(#.UnivQ _)
(do macro.Monad<Meta>
[[var-id varT] (&.with-type-env tc.var)]
(general analyse (maybe.assume (type.apply (list varT) inferT)) args))
(#.ExQ _)
(do macro.Monad<Meta>
[[ex-id exT] (&.with-type-env
tc.existential)]
(general analyse (maybe.assume (type.apply (list exT) inferT)) args))
(#.Apply inputT transT)
(case (type.apply (list inputT) transT)
(#.Some outputT)
(general analyse outputT args)
#.None
(&.throw Invalid-Type-Application (%type inferT)))
## Arguments are inferred back-to-front because, by convention,
## Lux functions take the most important arguments *last*, which
## means that the most information for doing proper inference is
## located in the last arguments to a function call.
## By inferring back-to-front, a lot of type-annotations can be
## avoided in Lux code, since the inference algorithm can piece
## things together more easily.
(#.Function inputT outputT)
(do macro.Monad<Meta>
[[outputT' args'A] (general analyse outputT args')
argA (&.with-stacked-errors
(function [_] (Cannot-Infer-Argument
(format "Inferred Type: " (%type inputT) "\n"
" Argument: " (%code argC))))
(&.with-type inputT
(analyse argC)))]
(wrap [outputT' (list& argA args'A)]))
(#.Var infer-id)
(do macro.Monad<Meta>
[?inferT' (&.with-type-env (tc.read infer-id))]
(case ?inferT'
(#.Some inferT')
(general analyse inferT' args)
_
(&.throw Cannot-Infer (cannot-infer inferT args))))
_
(&.throw Cannot-Infer (cannot-infer inferT args)))
))
## Turns a record type into the kind of function type suitable for inference.
(def: #export (record inferT)
(-> Type (Meta Type))
(case inferT
(#.Named name unnamedT)
(record unnamedT)
(^template [<tag>]
(<tag> env bodyT)
(do macro.Monad<Meta>
[bodyT+ (record bodyT)]
(wrap (<tag> env bodyT+))))
([#.UnivQ]
[#.ExQ])
(#.Apply inputT funcT)
(case (type.apply (list inputT) funcT)
(#.Some outputT)
(record outputT)
#.None
(&.throw Invalid-Type-Application (%type inferT)))
(#.Product _)
(macro/wrap (type.function (type.flatten-tuple inferT) inferT))
_
(&.throw Not-A-Record-Type (%type inferT))))
## Turns a variant type into the kind of function type suitable for inference.
(def: #export (variant tag expected-size inferT)
(-> Nat Nat Type (Meta Type))
(loop [depth +0
currentT inferT]
(case currentT
(#.Named name unnamedT)
(do macro.Monad<Meta>
[unnamedT+ (recur depth unnamedT)]
(wrap unnamedT+))
(^template [<tag>]
(<tag> env bodyT)
(do macro.Monad<Meta>
[bodyT+ (recur (n/inc depth) bodyT)]
(wrap (<tag> env bodyT+))))
([#.UnivQ]
[#.ExQ])
(#.Sum _)
(let [cases (type.flatten-variant currentT)
actual-size (list.size cases)
boundary (n/dec expected-size)]
(cond (or (n/= expected-size actual-size)
(and (n/> expected-size actual-size)
(n/< boundary tag)))
(case (list.nth tag cases)
(#.Some caseT)
(macro/wrap (if (n/= +0 depth)
(type.function (list caseT) currentT)
(let [replace! (replace-bound (|> depth n/dec (n/* +2)) inferT)]
(type.function (list (replace! caseT))
(replace! currentT)))))
#.None
(&common.variant-out-of-bounds-error inferT expected-size tag))
(n/< expected-size actual-size)
(&.throw Smaller-Variant-Than-Expected
(format "Expected: " (%i (nat-to-int expected-size)) "\n"
" Actual: " (%i (nat-to-int actual-size))))
(n/= boundary tag)
(let [caseT (type.variant (list.drop boundary cases))]
(macro/wrap (if (n/= +0 depth)
(type.function (list caseT) currentT)
(let [replace! (replace-bound (|> depth n/dec (n/* +2)) inferT)]
(type.function (list (replace! caseT))
(replace! currentT))))))
## else
(&common.variant-out-of-bounds-error inferT expected-size tag)))
(#.Apply inputT funcT)
(case (type.apply (list inputT) funcT)
(#.Some outputT)
(variant tag expected-size outputT)
#.None
(&.throw Invalid-Type-Application (%type inferT)))
_
(&.throw Not-A-Variant-Type (%type inferT)))))
|
