b7e220039f
This PR adds a hint to the "invalid projection" message suggesting the correct nested projection for expressions of the form `t.n` where `t` is a tuple and `n > 2`. This feature was originally proposed by @nomeata in #8986.
70 lines
2.5 KiB
Text
70 lines
2.5 KiB
Text
/-!
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# Hints for invalid tuple projections
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These tests assess hints for invalid projections that may be incorrectly attempting to project the
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`n`th element from a tuple where `n > 2`.
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-/
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def p : Nat × Nat × Nat := (3, 4, 5)
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/--
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error: Invalid projection: Index `3` is invalid for this structure; it must be between 1 and 2
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Note: The expression `p` has type `Nat × Nat × Nat` which has only 2 fields
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Hint: n-tuples in Lean are actually nested pairs. To access the 3rd component of this tuple, use the projection `.2.2` instead:
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3̵2̲.̲2̲
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-/
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#guard_msgs in
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#check p.3
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/--
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error: Invalid projection: Index `17` is invalid for this structure; it must be between 1 and 2
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Note: The expression `p` has type `Nat × Nat × Nat` which has only 2 fields
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Hint: n-tuples in Lean are actually nested pairs. For example, to access the "third" component of `(a, b, c)`, write `(a, b, c).2.2` instead of `(a, b, c).3`.
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-/
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#guard_msgs in
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#check p.17
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/--
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error: Invalid projection: Index `3` is invalid for this structure; it must be between 1 and 2
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Note: The expression `p` has type `Nat × Nat × Nat` which has only 2 fields
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Hint: n-tuples in Lean are actually nested pairs. To access the 3rd component of this tuple, use the projection `.2.2` instead:
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3̵2̲.̲2̲
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-/
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#guard_msgs in
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#check p.3.succ
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/-
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In prior versions of Lean, the below would erroneously produce two error messages: "structure type
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expected" on the first lval resolution iteration (prior to unfolding `MyProd`), then (correctly)
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"invalid index" on the second, post-unfolding iteration
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-/
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abbrev MyProd := Nat × Nat × Nat × Nat × Nat
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def mp : MyProd := (1, 2, 3, 4, 5)
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/--
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error: Invalid projection: Index `4` is invalid for this structure; it must be between 1 and 2
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Note: The expression `mp` has type `Nat × Nat × Nat × Nat × Nat` which has only 2 fields
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Hint: n-tuples in Lean are actually nested pairs. To access the 4th component of this tuple, use the projection `.2.2.2.1` instead:
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4̵2̲.̲2̲.̲2̲.̲1̲
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-/
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#guard_msgs in
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#eval mp.4
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-- Ensure we don't produce hints for synthetic syntax
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macro "illegally_project_from_a_tuple" : term => `((true, true, false).3)
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/--
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error: Invalid projection: Index `3` is invalid for this structure; it must be between 1 and 2
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Note: The expression `(true, true, false)` has type `Bool × Bool × Bool` which has only 2 fields
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Hint: n-tuples in Lean are actually nested pairs. For example, to access the "third" component of `(a, b, c)`, write `(a, b, c).2.2` instead of `(a, b, c).3`.
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-/
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#guard_msgs in
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#check illegally_project_from_a_tuple
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