Auto merge of #7568 - dtolnay-contrib:ifletelse, r=llogiq

Downgrade option_if_let_else to nursery

I believe that this lint's loose understanding of ownership (#5822, #6737) makes it unsuitable to be enabled by default in its current state, even as a pedantic lint.

Additionally the lint has known problems with type inference (#6137), though I may be willing to consider this a non-blocker in isolation if it weren't for the ownership false positives.

A fourth false positive involving const fn: #7567.

But on top of these, for me the biggest issue is I basically fully agree with https://github.com/rust-lang/rust-clippy/issues/6137#issuecomment-705605688. In my experience this lint universally makes code worse even when the resulting code does compile.

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changelog: remove [`option_if_let_else`] from default set of enabled lints

clippy_lints/src/lib.rs

@@ -1125,7 +1125,6 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(needless_for_each::NEEDLESS_FOR_EACH),
         LintId::of(needless_pass_by_value::NEEDLESS_PASS_BY_VALUE),
         LintId::of(non_expressive_names::SIMILAR_NAMES),
-        LintId::of(option_if_let_else::OPTION_IF_LET_ELSE),
         LintId::of(pass_by_ref_or_value::LARGE_TYPES_PASSED_BY_VALUE),
         LintId::of(pass_by_ref_or_value::TRIVIALLY_COPY_PASS_BY_REF),
         LintId::of(ranges::RANGE_MINUS_ONE),
@@ -1802,6 +1801,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(mutable_debug_assertion::DEBUG_ASSERT_WITH_MUT_CALL),
         LintId::of(mutex_atomic::MUTEX_INTEGER),
         LintId::of(nonstandard_macro_braces::NONSTANDARD_MACRO_BRACES),
+        LintId::of(option_if_let_else::OPTION_IF_LET_ELSE),
         LintId::of(path_buf_push_overwrite::PATH_BUF_PUSH_OVERWRITE),
         LintId::of(redundant_pub_crate::REDUNDANT_PUB_CRATE),
         LintId::of(regex::TRIVIAL_REGEX),

clippy_lints/src/option_if_let_else.rs

@@ -57,7 +57,7 @@ declare_clippy_lint! {
     /// }, |foo| foo);
     /// ```
     pub OPTION_IF_LET_ELSE,
-    pedantic,
+    nursery,
     "reimplementation of Option::map_or"
 }