[Merged by Bors] - fix(Data/Set/Image): simp confluence issues with image_subset_iff
#8683
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`image_subset_iff` is a questionable simp lemma because it converts an application of image into preimage unconditionally. This means that if any simp lemma applies to applications of images, there must be a corresponding lemma for applications of preimage. These lemmas are what I found missing after loogling.
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YaelDillies
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Co-authored-by: Yaël Dillies <yael.dillies@gmail.com>
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| @@ -654,6 +654,7 @@ theorem empty_ne_univ [Nonempty α] : (∅ : Set α) ≠ univ := fun e => | |||
| theorem subset_univ (s : Set α) : s ⊆ univ := fun _ _ => trivial | |||
| #align set.subset_univ Set.subset_univ | |||
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| @[simp] | |||
| theorem univ_subset_iff {s : Set α} : univ ⊆ s ↔ s = univ := | |||
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Would you mind adding the corresponding lemma for Finset?
Co-authored-by: Yaël Dillies <yael.dillies@gmail.com>
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I don't believe there is an analogous confluence issue for |
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🚀 Pull request has been placed on the maintainer queue by YaelDillies. |
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…8683) `image_subset_iff` is a questionable simp lemma because it converts an application of `Set.image` into an application of `Set.preimage` unconditionally. This means that if any simp lemma applies to images, there must be a corresponding lemma for preimages. These lemmas are what I found missing after loogling. I also added machine-checked examples of each confluence issue to a new file `tests/simp_confluence`.
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Pull request successfully merged into master. Build succeeded: |
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image_subset_iffimage_subset_iff
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…8683) `image_subset_iff` is a questionable simp lemma because it converts an application of `Set.image` into an application of `Set.preimage` unconditionally. This means that if any simp lemma applies to images, there must be a corresponding lemma for preimages. These lemmas are what I found missing after loogling. I also added machine-checked examples of each confluence issue to a new file `tests/simp_confluence`.
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image_subset_iffis a questionable simp lemma because it converts an application ofSet.imageinto an application ofSet.preimageunconditionally. This means that if any simp lemma applies to images, there must be a corresponding lemma for preimages. These lemmas are what I found missing after loogling.I also added machine-checked examples of each confluence issue to a new file
tests/simp_confluence.