Auto merge of #8418 - dtolnay-contrib:transmuteundefinedrepr, r=llogiq

Downgrade transmute_undefined_repr to nursery

Reason: #8417. I am skeptical of this lint but maybe there is a narrower subset of types on which it is useful, so keeping it for now but moving to nursery for further development.

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*Please write a short comment explaining your change (or "none" for internal only changes)*

changelog: Remove [`transmute_undefined_repr`] from default set of enabled lints

Author: bors

clippy_lints/src/lib.register_all.rs

@@ -277,7 +277,6 @@ store.register_group(true, "clippy::all", Some("clippy_all"), vec![
     LintId::of(transmute::TRANSMUTE_INT_TO_FLOAT),
     LintId::of(transmute::TRANSMUTE_NUM_TO_BYTES),
     LintId::of(transmute::TRANSMUTE_PTR_TO_REF),
-    LintId::of(transmute::TRANSMUTE_UNDEFINED_REPR),
     LintId::of(transmute::UNSOUND_COLLECTION_TRANSMUTE),
     LintId::of(transmute::WRONG_TRANSMUTE),
     LintId::of(transmuting_null::TRANSMUTING_NULL),

clippy_lints/src/lib.register_correctness.rs

@@ -58,7 +58,6 @@ store.register_group(true, "clippy::correctness", Some("clippy_correctness"), ve
     LintId::of(size_of_in_element_count::SIZE_OF_IN_ELEMENT_COUNT),
     LintId::of(swap::ALMOST_SWAPPED),
     LintId::of(to_string_in_display::TO_STRING_IN_DISPLAY),
-    LintId::of(transmute::TRANSMUTE_UNDEFINED_REPR),
     LintId::of(transmute::UNSOUND_COLLECTION_TRANSMUTE),
     LintId::of(transmute::WRONG_TRANSMUTE),
     LintId::of(transmuting_null::TRANSMUTING_NULL),

clippy_lints/src/lib.register_nursery.rs

@@ -26,6 +26,7 @@ store.register_group(true, "clippy::nursery", Some("clippy_nursery"), vec![
     LintId::of(strings::STRING_LIT_AS_BYTES),
     LintId::of(suspicious_operation_groupings::SUSPICIOUS_OPERATION_GROUPINGS),
     LintId::of(trailing_empty_array::TRAILING_EMPTY_ARRAY),
+    LintId::of(transmute::TRANSMUTE_UNDEFINED_REPR),
     LintId::of(transmute::USELESS_TRANSMUTE),
     LintId::of(use_self::USE_SELF),
 ])

clippy_lints/src/transmute/mod.rs

@@ -376,7 +376,7 @@ declare_clippy_lint! {
     /// ```
     #[clippy::version = "1.60.0"]
     pub TRANSMUTE_UNDEFINED_REPR,
-    correctness,
+    nursery,
     "transmute to or from a type with an undefined representation"
 }