add manual_pop_if lint

Add a lint to detect when the recently added Vec::pop_if,
VecDeque::pop_front_if, and VecDeque::pop_back_if are manually
implemented.

changelog: add [`manual_pop_if`] lint

Author: pbor

CHANGELOG.md

@@ -6705,6 +6705,7 @@ Released 2018-09-13
 [`manual_ok_or`]: https://rust-lang.github.io/rust-clippy/master/index.html#manual_ok_or
 [`manual_option_as_slice`]: https://rust-lang.github.io/rust-clippy/master/index.html#manual_option_as_slice
 [`manual_pattern_char_comparison`]: https://rust-lang.github.io/rust-clippy/master/index.html#manual_pattern_char_comparison
+[`manual_pop_if`]: https://rust-lang.github.io/rust-clippy/master/index.html#manual_pop_if
 [`manual_range_contains`]: https://rust-lang.github.io/rust-clippy/master/index.html#manual_range_contains
 [`manual_range_patterns`]: https://rust-lang.github.io/rust-clippy/master/index.html#manual_range_patterns
 [`manual_rem_euclid`]: https://rust-lang.github.io/rust-clippy/master/index.html#manual_rem_euclid

clippy_lints/src/declared_lints.rs

@@ -312,6 +312,7 @@ pub static LINTS: &[&::declare_clippy_lint::LintInfo] = &[
     crate::manual_main_separator_str::MANUAL_MAIN_SEPARATOR_STR_INFO,
     crate::manual_non_exhaustive::MANUAL_NON_EXHAUSTIVE_INFO,
     crate::manual_option_as_slice::MANUAL_OPTION_AS_SLICE_INFO,
+    crate::manual_pop_if::MANUAL_POP_IF_INFO,
     crate::manual_range_patterns::MANUAL_RANGE_PATTERNS_INFO,
     crate::manual_rem_euclid::MANUAL_REM_EUCLID_INFO,
     crate::manual_retain::MANUAL_RETAIN_INFO,

clippy_lints/src/lib.rs

@@ -211,6 +211,7 @@ mod manual_let_else;
 mod manual_main_separator_str;
 mod manual_non_exhaustive;
 mod manual_option_as_slice;
+mod manual_pop_if;
 mod manual_range_patterns;
 mod manual_rem_euclid;
 mod manual_retain;
@@ -864,6 +865,7 @@ pub fn register_lint_passes(store: &mut rustc_lint::LintStore, conf: &'static Co
         Box::new(move |tcx| Box::new(duration_suboptimal_units::DurationSuboptimalUnits::new(tcx, conf))),
         Box::new(move |_| Box::new(manual_take::ManualTake::new(conf))),
         Box::new(|_| Box::new(manual_checked_ops::ManualCheckedOps)),
+        Box::new(move |_| Box::new(manual_pop_if::ManualPopIf::new(conf))),
         // add late passes here, used by `cargo dev new_lint`
     ];
     store.late_passes.extend(late_lints);