407a59d697
This PR modifies the pretty printing of pi types. Now `∀` will be preferred over `→` for propositions if the domain is not a proposition. For example, `∀ (n : Nat), True` pretty prints as `∀ (n : Nat), True` rather than as `Nat → True`. There is also now an option `pp.foralls` (default true) that when false disables using `∀` at all, for pedagogical purposes. This PR also adjusts instance implicit binder pretty printing — nondependent pi types won't show the instance binder name. Closes #1834. The linked RFC also suggests using `_` for binder names in case of non-dependance. We're tabling that idea. Potentially it is useful for hygienic names; this could improve how `Nat → True` pretty prints as `∀ (a : Nat), True`, with this `a` that's chosen by implication notation elaboration. Relatedly, this PR exposes even further the issue where binder names are reused in a confusing way. Consider: `Nat → Nat → (a : Nat) → a = a` pretty prints as `∀ (a a a : Nat), a = a`.
21 lines
942 B
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21 lines
942 B
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synthorder.lean:4:0-4:40: error: instance does not provide concrete values for (semi-)out-params
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Foo A (B × ?C)
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synthorder.lean:7:0-7:38: error: cannot find synthesization order for instance @instFooNat with type
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{A : Type} → [Foo A Nat] → Foo Nat A
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all remaining arguments have metavariables:
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Foo ?A Nat
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[Meta.synthOrder] synthesizing the arguments of @instFoo in the order [3, 4]:
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Foo A B
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Foo B C
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[Meta.synthOrder] synthesizing the arguments of @instFoo_1 in the order [4, 3]:
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Foo A B
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Foo B C
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[Meta.synthOrder] synthesizing the arguments of @instFooOption in the order []:
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[Meta.synthOrder] synthesizing the arguments of @TwoHalf.toTwo in the order [2]:
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TwoHalf α
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[Meta.synthOrder] synthesizing the arguments of @Four.toThree in the order [4]:
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Four α β
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[Meta.synthOrder] synthesizing the arguments of @instFourOfThree in the order [4, 2, 3]:
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Three α β
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One β
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TwoHalf β
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