[Merged by Bors] - fix(NumberTheory/LegendreSymbol/AddCharacter): Disentangle coercion mess for AddChar
#8803
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There are two things going on here: * `AddChar G R` has two syntactically different coercions to function `G → R`: * `FunLike.coe` via `AddChar.monoidHomClass` * `AddChar.toFun` via `AddChar.hasCoeToFun` * `AddChar.hasCoeToFun` and `AddChar.monoidHomClass` together create a diamond for the typeclass problem `FunLike (AddChar G R) _ _` This PR fixes both problems by * removing the `HasCoeToFun` instance and the corresponding `AddChar.toFun` * changing `MonoidHomClass (AddChar G R) (Multiplicative G) R` to `FunLike (AddChar G R) G fun _ ↦ R` (isn't the whole point of `AddChar` to go from an additive group to a multiplicative one anyway?) This PR isn't meant to be perfect. It is a stopgag to an issue that has completely startled progress on LeanAPAP. Once it is fixed, a much more thorough refactor will follow.
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Co-authored-by: Eric Wieser <wieser.eric@gmail.com>
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…ess for `AddChar` (#8803) There are two things going on here: * `AddChar G R` has two syntactically different coercions to function `G → R`: * `FunLike.coe` via `AddChar.monoidHomClass` * `AddChar.toFun` via `AddChar.hasCoeToFun` * `AddChar.hasCoeToFun` and `AddChar.monoidHomClass` together create a diamond for the typeclass problem `FunLike (AddChar G R) _ _` This PR fixes both problems by * removing the `HasCoeToFun` instance and the corresponding `AddChar.toFun` * changing `MonoidHomClass (AddChar G R) (Multiplicative G) R` to `FunLike (AddChar G R) G fun _ ↦ R` (isn't the whole point of `AddChar` to go from an additive group to a multiplicative one anyway?) This PR isn't meant to be perfect. It is a stopgag to an issue that has completely startled progress on LeanAPAP. Once it is fixed, a much more thorough refactor will follow. This breaks a rewrite downstream that now unifies to some defeq but not syntactically equal type. This is more an indication of fragility in the original proof.
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…ess for `AddChar` (#8803) There are two things going on here: * `AddChar G R` has two syntactically different coercions to function `G → R`: * `FunLike.coe` via `AddChar.monoidHomClass` * `AddChar.toFun` via `AddChar.hasCoeToFun` * `AddChar.hasCoeToFun` and `AddChar.monoidHomClass` together create a diamond for the typeclass problem `FunLike (AddChar G R) _ _` This PR fixes both problems by * removing the `HasCoeToFun` instance and the corresponding `AddChar.toFun` * changing `MonoidHomClass (AddChar G R) (Multiplicative G) R` to `FunLike (AddChar G R) G fun _ ↦ R` (isn't the whole point of `AddChar` to go from an additive group to a multiplicative one anyway?) This PR isn't meant to be perfect. It is a stopgag to an issue that has completely startled progress on LeanAPAP. Once it is fixed, a much more thorough refactor will follow. This breaks a rewrite downstream that now unifies to some defeq but not syntactically equal type. This is more an indication of fragility in the original proof.
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…ess for `AddChar` (#8803) There are two things going on here: * `AddChar G R` has two syntactically different coercions to function `G → R`: * `FunLike.coe` via `AddChar.monoidHomClass` * `AddChar.toFun` via `AddChar.hasCoeToFun` * `AddChar.hasCoeToFun` and `AddChar.monoidHomClass` together create a diamond for the typeclass problem `FunLike (AddChar G R) _ _` This PR fixes both problems by * removing the `HasCoeToFun` instance and the corresponding `AddChar.toFun` * changing `MonoidHomClass (AddChar G R) (Multiplicative G) R` to `FunLike (AddChar G R) G fun _ ↦ R` (isn't the whole point of `AddChar` to go from an additive group to a multiplicative one anyway?) This PR isn't meant to be perfect. It is a stopgag to an issue that has completely startled progress on LeanAPAP. Once it is fixed, a much more thorough refactor will follow. This breaks a rewrite downstream that now unifies to some defeq but not syntactically equal type. This is more an indication of fragility in the original proof.
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There are two things going on here:
AddChar G Rhas two syntactically different coercions to functionG → R:FunLike.coeviaAddChar.monoidHomClassAddChar.toFunviaAddChar.hasCoeToFunAddChar.hasCoeToFunandAddChar.monoidHomClasstogether create a diamond for the typeclass problemFunLike (AddChar G R) _ _This PR fixes both problems by
HasCoeToFuninstance and the correspondingAddChar.toFunMonoidHomClass (AddChar G R) (Multiplicative G) RtoFunLike (AddChar G R) G fun _ ↦ R(isn't the whole point ofAddCharto go from an additive group to a multiplicative one anyway?)This PR isn't meant to be perfect. It is a stopgag to an issue that has completely startled progress on LeanAPAP. Once it is fixed, a much more thorough refactor will follow.
This breaks a rewrite downstream that now unifies to some defeq but not syntactically equal type.
This is more an indication of fragility in the original proof.