Revert rust-lang#6796: Downgrade manual_map to nursery

Author: Jarcho

clippy_lints/src/lib.rs

@@ -1540,6 +1540,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(&loops::WHILE_LET_ON_ITERATOR),
         LintId::of(&main_recursion::MAIN_RECURSION),
         LintId::of(&manual_async_fn::MANUAL_ASYNC_FN),
+        LintId::of(&manual_map::MANUAL_MAP),
         LintId::of(&manual_non_exhaustive::MANUAL_NON_EXHAUSTIVE),
         LintId::of(&manual_strip::MANUAL_STRIP),
         LintId::of(&manual_unwrap_or::MANUAL_UNWRAP_OR),
@@ -1770,6 +1771,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(&loops::WHILE_LET_ON_ITERATOR),
         LintId::of(&main_recursion::MAIN_RECURSION),
         LintId::of(&manual_async_fn::MANUAL_ASYNC_FN),
+        LintId::of(&manual_map::MANUAL_MAP),
         LintId::of(&manual_non_exhaustive::MANUAL_NON_EXHAUSTIVE),
         LintId::of(&map_clone::MAP_CLONE),
         LintId::of(&matches::INFALLIBLE_DESTRUCTURING_MATCH),
@@ -2045,7 +2047,6 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(&floating_point_arithmetic::SUBOPTIMAL_FLOPS),
         LintId::of(&future_not_send::FUTURE_NOT_SEND),
         LintId::of(&let_if_seq::USELESS_LET_IF_SEQ),
-        LintId::of(&manual_map::MANUAL_MAP),
         LintId::of(&missing_const_for_fn::MISSING_CONST_FOR_FN),
         LintId::of(&mutable_debug_assertion::DEBUG_ASSERT_WITH_MUT_CALL),
         LintId::of(&mutex_atomic::MUTEX_INTEGER),

clippy_lints/src/manual_map.rs

@@ -23,7 +23,7 @@ declare_clippy_lint! {
     ///
     /// **Why is this bad?** Using the `map` method is clearer and more concise.
     ///
-    /// **Known problems:** `map` is not capable of representing some control flow which works fine in `match`.
+    /// **Known problems:** None.
     ///
     /// **Example:**
     ///
@@ -38,7 +38,7 @@ declare_clippy_lint! {
     /// Some(0).map(|x| x + 1);
     /// ```
     pub MANUAL_MAP,
-    nursery,
+    style,
     "reimplementation of `map`"
 }