c427fb4086
The new folder will contain the new parser, macro expander and compiler. This commit also renames the namespace for the old parser `lean3.parser`
88 lines
3.8 KiB
Text
88 lines
3.8 KiB
Text
/-
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Copyright (c) 2017 Microsoft Corporation. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Authors: Sebastian Ullrich
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Attribute that can automatically derive typeclass instances.
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-/
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prelude
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import init.meta.attribute
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import init.meta.interactive_base
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import init.meta.mk_has_reflect_instance
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open lean3
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open interactive.types
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open tactic
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/-- A handler that may or may not be able to implement the typeclass `cls` for `decl`.
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It should return `tt` if it was able to derive `cls` and `ff` if it does not know
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how to derive `cls`, in which case lower-priority handlers will be tried next. -/
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meta def derive_handler := Π (cls : pexpr) (decl : name), tactic bool
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@[user_attribute]
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meta def derive_handler_attr : user_attribute :=
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{ name := `derive_handler, descr := "register a definition of type `derive_handler` for use in the [derive] attribute" }
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private meta def try_handlers (p : pexpr) (n : name) : list derive_handler → tactic unit
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| [] := fail format!"failed to find a derive handler for '{p}'"
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| (h::hs) :=
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do success ← h p n,
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when (¬success) $
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try_handlers hs
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@[user_attribute] meta def derive_attr : user_attribute unit (list pexpr) :=
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{ name := `derive, descr := "automatically derive typeclass instances",
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parser := pexpr_list_or_texpr,
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after_set := some (λ n _ _,
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do ps ← derive_attr.get_param n,
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handlers ← attribute.get_instances `derive_handler,
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handlers ← handlers.mmap (λ n, eval_expr derive_handler (expr.const n [])),
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ps.mmap' (λ p, try_handlers p n handlers)) }
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/-- Given a tactic `tac` that can solve an application of `cls` in the right context,
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`instance_derive_handler` uses it to build an instance declaration of `cls n`. -/
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meta def instance_derive_handler (cls : name) (tac : tactic unit) (univ_poly := tt)
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(modify_target : name → list expr → expr → tactic expr := λ _ _, pure) : derive_handler :=
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λ p n,
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if p.is_constant_of cls then
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do decl ← get_decl n,
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cls_decl ← get_decl cls,
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env ← get_env,
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guard (env.is_inductive n) <|> fail format!"failed to derive '{cls}', '{n}' is not an inductive type",
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let ls := decl.univ_params.map $ λ n, if univ_poly then level.param n else level.zero,
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-- incrementally build up target expression `Π (hp : p) [cls hp] ..., cls (n.{ls} hp ...)`
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-- where `p ...` are the inductive parameter types of `n`
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let tgt : expr := expr.const n ls,
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⟨params, _⟩ ← mk_local_pis (decl.type.instantiate_univ_params (decl.univ_params.zip ls)),
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let tgt := tgt.mk_app params,
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tgt ← mk_app cls [tgt],
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tgt ← modify_target n params tgt,
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tgt ← params.enum.mfoldr (λ ⟨i, param⟩ tgt,
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do -- add typeclass hypothesis for each inductive parameter
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tgt ← do {
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guard $ i < env.inductive_num_params n,
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param_cls ← mk_app cls [param],
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-- TODO(sullrich): omit some typeclass parameters based on usage of `param`?
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pure $ expr.pi `a binder_info.inst_implicit param_cls tgt
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} <|> pure tgt,
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pure $ tgt.bind_pi param
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) tgt,
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(_, val) ← tactic.solve_aux tgt (intros >> tac),
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val ← instantiate_mvars val,
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let trusted := decl.is_trusted ∧ cls_decl.is_trusted,
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add_decl (declaration.defn (n ++ cls)
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(if univ_poly then decl.univ_params else [])
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tgt val reducibility_hints.abbrev trusted),
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set_basic_attribute `instance (n ++ cls) tt,
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pure true
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else pure false
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@[derive_handler] meta def has_reflect_derive_handler :=
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instance_derive_handler ``has_reflect mk_has_reflect_instance ff (λ n params tgt,
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-- add additional `reflected` assumption for each parameter
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params.mfoldr (λ param tgt,
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do param_cls ← mk_app `reflected [param],
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pure $ expr.pi `a binder_info.inst_implicit param_cls tgt
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) tgt)
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attribute [derive has_reflect] bool prod sum option interactive.loc pos
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