7ed716f904
This PR improves the error messages produced by invalid projections and field notation. It also adds a hint to the "function expected" error message noting the argument to which the term is being applied, which can be helpful for debugging spurious "function expected" messages actually caused by syntax errors. --------- Co-authored-by: Joachim Breitner <mail@joachim-breitner.de>
80 lines
2 KiB
Text
80 lines
2 KiB
Text
/-!
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# Regression test for autoparam panic in `inductive` parameters
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In the issue https://github.com/leanprover/lean4/issues/7788
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there's an error that appears in these circumstances:
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Given an `inductive` command whose header induces an autoparam,
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and that autoparam has a metavariable in its type,
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then there is a panic in `Expr.fvarId!`.
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The problem came from not properly handling metavariables that appear in the parameter list,
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which is how autoparams handle metavariables in their types (allowing them to be specialized later,
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rather than committing to a free variable).
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The fix was to be sure to abstract the parameters to create the type constructor types
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(which incidentally simplified the handling of mutual inductives).
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-/
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set_option pp.mvars false
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namespace Ex1
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def const (a : A) (_ : B) := a
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/-!
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Here, `A` has an underdetermined type.
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This results in two autoimplicits, one for `A` and one for its type.
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-/
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inductive X (h : const Unit A) where
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| a
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/-- info: Ex1.X.{u_1} {x✝ : Sort u_1} {A : x✝} (h : const Unit A) : Type -/
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#guard_msgs in #check X
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/-!
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Because `A` and its type are abstracted at header elaboration time,
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it is too late to be able to specialize its type from within the constructor.
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-/
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/--
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error: type expected, got
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(A : x✝)
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-/
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#guard_msgs in
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inductive X' (h : const Unit A) where
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| a (x : A)
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end Ex1
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namespace Ex2
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def const (a : A) (_ : B) := a
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/-!
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Make sure that `structure` can handle setting all the parameters to implicit
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when processing default values.
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(There used to be code that was conditional on a parameter being an fvar.)
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-/
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structure S (a : const Unit A) where
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x := a
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/-- info: Ex2.S.x._default.{u_1} {x✝ : Sort u_1} {A : x✝} {a : const Unit A} : const Unit A -/
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#guard_msgs in #check S.x._default
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end Ex2
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namespace Ex3
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/-!
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Example from issue #7788. Used to panic.
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-/
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/--
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error: Function expected at
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A
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but this term has type
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?_
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Note: Expected a function because this term is being applied to the argument
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1
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-/
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#guard_msgs in inductive X (h : A 1) where
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end Ex3
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