Properly reject higher-rank types during promotion/singling #406
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`singletons` can't handle higher-rank types. You might think that these sorts of types would naturally be rejected when promoting or singling them, but that actually turns out not to be the case! (See #401 for examples of higher-rank types that squeeze through the cracks.) Luckily, the additional machinery that `th-desuguar` adds in goldfirere/th-desugar#125 makes it much easier to detect these. Instead of using `unravelDType` to decompose a function type (which permits all sorts of higher-rank gubbins), we use a restricted version called `unravelVanillaDType`, which throws an error if anything higher-rank is detected. See `Note [Vanilla-type validity checking during promotion]` in `D.S.Promote.Type` for a full explanation of what a "vanilla" type is. Fixes #401.
goldfirere
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Sep 3, 2019
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Ship it! |
RyanGlScott
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Nov 2, 2019
There was one place where #406 forgot to check for higher-rank types: the types of data constructors. Easily fixed.
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singletonscan't handle higher-rank types. You might think that these sorts of types would naturally be rejected when promoting or singling them, but that actually turns out not to be the case! (See #401 for examples of higher-rank types that squeeze through the cracks.)Luckily, the additional machinery that
th-desuguaradds in goldfirere/th-desugar#125 makes it much easier to detect these. Instead of usingunravelDTypeto decompose a function type (which permits all sorts of higher-rank gubbins), we use a restricted version calledunravelVanillaDType, which throws an error if anything higher-rank is detected. SeeNote [Vanilla-type validity checking during promotion]inD.S.Promote.Typefor a full explanation of what a "vanilla" type is.Fixes #401.