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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)))))
|
