793cd14b38
This PR improves the message of `unusedVariables` linter, by replacing potentially confusing "unused variable `x`" message with "Variable name `x` is not explicitly referenced. The binding can be removed (if unused) or named `_` (if used implicitly)." Related issue: https://github.com/leanprover/lean4/issues/13269
68 lines
2.3 KiB
Text
68 lines
2.3 KiB
Text
/-
|
||
This is an example posted by Wrenna Robson on Zulip.
|
||
-/
|
||
|
||
-- Reference
|
||
def idxToCount [BEq α] (xs : List α) (i : Nat) (hi : i < xs.length) : Nat := go xs i hi 0 where
|
||
@[specialize] go : (xs : List α) → (i : Nat) → i < xs.length → Nat → Nat
|
||
| _ :: _, 0, _, acc => acc
|
||
| x :: xs, i + 1, hi, acc =>
|
||
haveI hi := Nat.lt_of_succ_lt_succ hi
|
||
bif x == xs[i] then go xs i hi (acc + 1) else go xs i hi acc
|
||
|
||
-- `go` does not depend on the outer `xs` as expected.
|
||
/--
|
||
info: idxToCount.go.{u_1} {α : Type u_1} [BEq α] (xs : List α) (i : Nat) : i < xs.length → Nat → Nat
|
||
-/
|
||
#guard_msgs in
|
||
#check idxToCount.go
|
||
|
||
|
||
def idxToCount' [BEq α] (xs : List α) (i : Nat) (hi : i < xs.length) : Nat := go xs i hi 0 where
|
||
@[specialize] go : (xs : List α) → (i : Nat) → i < xs.length → Nat → Nat
|
||
| _ :: _, 0, _, acc => acc
|
||
| x :: xs, i + 1, hi, acc =>
|
||
bif x == xs[i]'(by grind) then go xs i (by grind) (acc + 1) else go xs i (by grind) acc
|
||
|
||
/-
|
||
`grind +revert` was the default behavior until v4.25.1
|
||
Thus, `go` used to depend on the outer `xs`. This is not the case anymore.
|
||
-/
|
||
/--
|
||
info: idxToCount'.go.{u_1} {α : Type u_1} [BEq α] (xs : List α) (i : Nat) : i < xs.length → Nat → Nat
|
||
-/
|
||
#guard_msgs in
|
||
#check idxToCount'.go
|
||
|
||
/-
|
||
We can reproduce the behavior of v4.25.1 using `grind +revert`.
|
||
-/
|
||
def idxToCount'' [BEq α] (xs : List α) (i : Nat) (hi : i < xs.length) : Nat := go xs i hi 0 where
|
||
@[specialize] go : (xs : List α) → (i : Nat) → i < xs.length → Nat → Nat
|
||
| _ :: _, 0, _, acc => acc
|
||
| x :: xs, i + 1, hi, acc =>
|
||
bif x == xs[i]'(by grind +revert) then go xs i (by grind +revert) (acc + 1) else go xs i (by grind +revert) acc
|
||
|
||
/--
|
||
info: idxToCount''.go.{u_1} {α : Type u_1} [BEq α] (xs : List α) (i : Nat) (hi : i < xs.length) (xs✝ : List α) (i✝ : Nat) :
|
||
i✝ < xs✝.length → Nat → Nat
|
||
-/
|
||
#guard_msgs in
|
||
#check idxToCount''.go
|
||
|
||
set_option linter.unusedVariables true
|
||
-- Another example from the Zulip thread
|
||
/--
|
||
warning: Variable name `hi` is not explicitly referenced.
|
||
|
||
The binding can be removed (if unused) or named `_` (if used implicitly).
|
||
|
||
Note: This linter can be disabled with `set_option linter.unusedVariables false`
|
||
-/
|
||
#guard_msgs in
|
||
def oops (oh_no : List Nat) (hi : 0 < oh_no.length) : True := go where
|
||
go : True := by grind
|
||
|
||
/-- info: oops.go : True -/
|
||
#guard_msgs in
|
||
#check oops.go
|