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### Description of the problem
`Opaque ` gives the error "cannot set an inductive type or a constructor as transparent", which makes no sense. Maybe the message should say "You cannot set the opac…
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### Prerequisites
Please put an X between the brackets as you perform the following steps:
* [X] Check that your issue is not already filed:
https://github.com/leanprover/lean4/issues
* …
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This is to raise some thoughts on the possibility of having higher inductive types in the future, even just for paths to begin with (so in the Standard HoTT sense).
For example, having [pushouts](htt…
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### Description
Today, Lean accepts all of the following:
```
inductive DogSound
| woof
| grr
```
```
inductive DogSound :=
| woof
| grr
```
```
inductive DogSound where…
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### Prerequisites
Please put an X between the brackets as you perform the following steps:
* [X] Check that your issue is not already filed:
https://github.com/leanprover/lean4/issues
* …
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**Describe the bug**
This came up on Zulip:
> at the explanation for the [requirements for inductive types](https://lean-lang.org/doc/reference/latest/The-Lean-Language/The-Type-System/#well-formed-…
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When defining new objects and inductive types in one ```MetaCoq Run``` call from their ```term``` AST, if your definitions are dependent, it can lead to a universe level error not present when definin…
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We now always fail with ambiguity on inductive cycles, even in the old solver https://github.com/rust-lang/rust/pull/118649
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The old solver returns `EvaluatedToRecur` on inductive cycles whic…
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Currently the theory supports one main recursive type, the natural numbers. This type is treated in a somewhat ad hoc way: modalities can contain a special function *nr* that is used in one usage rule…
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Lately, I have written a Coq file to verify a data structure.
This data structure is called catenable deques, a queue supporting push, pop, inject (push at the end), eject (pop at the end) and con…