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>
70 lines
1.4 KiB
Text
70 lines
1.4 KiB
Text
/-!
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# Tests for issue #6400
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https://github.com/leanprover/lean4/issues/6400
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Nested field notation was not resolving correctly if there was generalized field notation coming first
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and the target wasn't the first explicit argument.
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-/
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/-!
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Example from issue #6400
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-/
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namespace Ex1
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structure S where
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x : Nat
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class Class where
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s : S
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def Class.foo [c : Class] : S := c.s
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-- Always worked
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example [c : Class] : S := c.foo
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-- Parens made it work
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example [c : Class] : Nat := (c.foo).x
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-- Formerly, "function expected at Class.foo"
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example [c : Class] : Nat := c.foo.x
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end Ex1
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/-!
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Fixed recursive calls too, which had the same problem.
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-/
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def Nat.f {n : Nat} : Nat :=
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match n with
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| 0 => 0
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| n + 1 => n.f.succ
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/-!
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Now instances are unfolded when searching for a relevant argument.
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-/
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namespace Ex2
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class Friend (α : Type) where
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friend : Type
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instance : Friend Nat where
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friend := Bool
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def _root_.Bool.f (b : Friend.friend Nat) := !b
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variable (a : Bool)
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/-- info: a.f : Bool -/
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#guard_msgs in #check a.f
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-- Semireducible definitions are not unfolded however.
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def semifriend (α : Type) [Friend α] := Friend.friend α
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def _root_.Bool.g (b : semifriend Nat) := !b
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/--
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error: Invalid field notation: Function `Bool.g` does not have a usable parameter of type `Bool` for which to substitute `a`
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Note: Such a parameter must be explicit, or implicit with a unique name, to be used by field notation
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-/
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#guard_msgs in #check a.g
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end Ex2
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