Guts of trait reform: Reimplement trait matching algorithm #17197
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nikomatsakis
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Argh. I just merged this this morning, but I already see merge conflicts! Probably best to do review now and I'll patch it up afterwards. |
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Note: see doc.rs for an intro to the trait matching code. |
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Very excited to see this close to landing! |
nikomatsakis
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rebased so that it is mergable |
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rebased: correct typos |
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Address nits and refactor the trait resolution that is specific to trans into trans. |
see the lang-items for Sized etc. @acrichto and @thestinger had no objections.
- Unify the "well-formedness" checking that typeck was already doing with what was taking place in kind. - Move requirements that things be sized into typeck. - I left the checking on upvars in kind, though I think it should eventually be refactored into regionck (which would perhaps be renamed). This reflects a general plan to convert typeck so that it registers obligations or other pending things for conditions it cannot check eventually. This makes it easier to identify all the conditions that apply to an AST expression, but can also influence inference in somec cases (e.g., `Send` implies `'static`, so I already had to promote a lot of the checking that `kind.rs` was doing into typeck, this branch just continues the process).
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Rebased. |
bors
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Sep 16, 2014
…sited, r=pcwalton This patch does not make many functional changes, but does a lot of restructuring towards the goals of #5527. This is the biggest patch, basically, that should enable most of the other patches in a relatively straightforward way. Major changes: - Do not track impls through trans, instead recompute as needed. - Isolate trait matching code into its own module, carefully structure to distinguish various phases (selection vs confirmation vs fulfillment) - Consider where clauses in their more general form - Integrate checking of builtin bounds into the trait matching process, rather than doing it separately in kind.rs (important for opt-in builtin bounds) What is not included: - Where clauses are still not generalized. This should be a straightforward follow-up patch. - Caching. I did not include much caching. I have plans for various kinds of caching we can do. Should be straightforward. Preliminary perf measurements suggested that this branch keeps compilation times roughly what they are. - Method resolution. The initial algorithm I proposed for #5527 does not work as well as I hoped. I have a revised plan which is much more similar to what we do today. - Deref vs deref-mut. The initial fix I had worked great for autoderef, but not for explicit deref. - Permitting blanket impls to overlap with specific impls. Initial plan to consider all nested obligations before considering an impl to match caused many compilation errors. We have a revised plan but it is not implemented here, should be a relatively straightforward extension.
bors
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Sep 16, 2014
…sited, r=pcwalton This patch does not make many functional changes, but does a lot of restructuring towards the goals of #5527. This is the biggest patch, basically, that should enable most of the other patches in a relatively straightforward way. Major changes: - Do not track impls through trans, instead recompute as needed. - Isolate trait matching code into its own module, carefully structure to distinguish various phases (selection vs confirmation vs fulfillment) - Consider where clauses in their more general form - Integrate checking of builtin bounds into the trait matching process, rather than doing it separately in kind.rs (important for opt-in builtin bounds) What is not included: - Where clauses are still not generalized. This should be a straightforward follow-up patch. - Caching. I did not include much caching. I have plans for various kinds of caching we can do. Should be straightforward. Preliminary perf measurements suggested that this branch keeps compilation times roughly what they are. - Method resolution. The initial algorithm I proposed for #5527 does not work as well as I hoped. I have a revised plan which is much more similar to what we do today. - Deref vs deref-mut. The initial fix I had worked great for autoderef, but not for explicit deref. - Permitting blanket impls to overlap with specific impls. Initial plan to consider all nested obligations before considering an impl to match caused many compilation errors. We have a revised plan but it is not implemented here, should be a relatively straightforward extension.
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This patch does not make many functional changes, but does a lot of restructuring towards the goals of #5527. This is the biggest patch, basically, that should enable most of the other patches in a relatively straightforward way.
Major changes:
What is not included: