diff --git a/CHANGELOG.md b/CHANGELOG.md
index 64864c2e278..a91b7c64770 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1996,6 +1996,7 @@ Released 2018-09-13
[`inline_asm_x86_att_syntax`]: https://rust-lang.github.io/rust-clippy/master/index.html#inline_asm_x86_att_syntax
[`inline_asm_x86_intel_syntax`]: https://rust-lang.github.io/rust-clippy/master/index.html#inline_asm_x86_intel_syntax
[`inline_fn_without_body`]: https://rust-lang.github.io/rust-clippy/master/index.html#inline_fn_without_body
+[`inspect_for_each`]: https://rust-lang.github.io/rust-clippy/master/index.html#inspect_for_each
[`int_plus_one`]: https://rust-lang.github.io/rust-clippy/master/index.html#int_plus_one
[`integer_arithmetic`]: https://rust-lang.github.io/rust-clippy/master/index.html#integer_arithmetic
[`integer_division`]: https://rust-lang.github.io/rust-clippy/master/index.html#integer_division
diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs
index f12994c7a60..17662b81205 100644
--- a/clippy_lints/src/lib.rs
+++ b/clippy_lints/src/lib.rs
@@ -733,6 +733,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
&methods::FROM_ITER_INSTEAD_OF_COLLECT,
&methods::GET_UNWRAP,
&methods::INEFFICIENT_TO_STRING,
+ &methods::INSPECT_FOR_EACH,
&methods::INTO_ITER_ON_REF,
&methods::ITERATOR_STEP_BY_ZERO,
&methods::ITER_CLONED_COLLECT,
@@ -1507,6 +1508,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
LintId::of(&methods::FILTER_NEXT),
LintId::of(&methods::FLAT_MAP_IDENTITY),
LintId::of(&methods::FROM_ITER_INSTEAD_OF_COLLECT),
+ LintId::of(&methods::INSPECT_FOR_EACH),
LintId::of(&methods::INTO_ITER_ON_REF),
LintId::of(&methods::ITERATOR_STEP_BY_ZERO),
LintId::of(&methods::ITER_CLONED_COLLECT),
@@ -1807,6 +1809,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
LintId::of(&methods::CLONE_ON_COPY),
LintId::of(&methods::FILTER_NEXT),
LintId::of(&methods::FLAT_MAP_IDENTITY),
+ LintId::of(&methods::INSPECT_FOR_EACH),
LintId::of(&methods::OPTION_AS_REF_DEREF),
LintId::of(&methods::SEARCH_IS_SOME),
LintId::of(&methods::SKIP_WHILE_NEXT),
diff --git a/clippy_lints/src/methods/inspect_for_each.rs b/clippy_lints/src/methods/inspect_for_each.rs
new file mode 100644
index 00000000000..6d41ee38a27
--- /dev/null
+++ b/clippy_lints/src/methods/inspect_for_each.rs
@@ -0,0 +1,23 @@
+use rustc_hir as hir;
+use rustc_lint::LateContext;
+use rustc_span::source_map::Span;
+
+use crate::utils::{match_trait_method, paths, span_lint_and_help};
+
+use super::INSPECT_FOR_EACH;
+
+/// lint use of `inspect().for_each()` for `Iterators`
+pub(super) fn lint<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>, inspect_span: Span) {
+ if match_trait_method(cx, expr, &paths::ITERATOR) {
+ let msg = "called `inspect(..).for_each(..)` on an `Iterator`";
+ let hint = "move the code from `inspect(..)` to `for_each(..)` and remove the `inspect(..)`";
+ span_lint_and_help(
+ cx,
+ INSPECT_FOR_EACH,
+ inspect_span.with_hi(expr.span.hi()),
+ msg,
+ None,
+ hint,
+ );
+ }
+}
diff --git a/clippy_lints/src/methods/mod.rs b/clippy_lints/src/methods/mod.rs
index f13f2491d6e..018696ef0cf 100644
--- a/clippy_lints/src/methods/mod.rs
+++ b/clippy_lints/src/methods/mod.rs
@@ -1,5 +1,6 @@
mod bind_instead_of_map;
mod inefficient_to_string;
+mod inspect_for_each;
mod manual_saturating_arithmetic;
mod option_map_unwrap_or;
mod unnecessary_filter_map;
@@ -1405,6 +1406,36 @@ declare_clippy_lint! {
"use `.collect()` instead of `::from_iter()`"
}
+declare_clippy_lint! {
+ /// **What it does:** Checks for usage of `inspect().for_each()`.
+ ///
+ /// **Why is this bad?** It is the same as performing the computation
+ /// inside `inspect` at the beginning of the closure in `for_each`.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ ///
+ /// ```rust
+ /// [1,2,3,4,5].iter()
+ /// .inspect(|&x| println!("inspect the number: {}", x))
+ /// .for_each(|&x| {
+ /// assert!(x >= 0);
+ /// });
+ /// ```
+ /// Can be written as
+ /// ```rust
+ /// [1,2,3,4,5].iter()
+ /// .for_each(|&x| {
+ /// println!("inspect the number: {}", x);
+ /// assert!(x >= 0);
+ /// });
+ /// ```
+ pub INSPECT_FOR_EACH,
+ complexity,
+ "using `.inspect().for_each()`, which can be replaced with `.for_each()`"
+}
+
pub struct Methods {
msrv: Option<RustcVersion>,
}
@@ -1467,6 +1498,7 @@ impl_lint_pass!(Methods => [
UNNECESSARY_LAZY_EVALUATIONS,
MAP_COLLECT_RESULT_UNIT,
FROM_ITER_INSTEAD_OF_COLLECT,
+ INSPECT_FOR_EACH,
]);
impl<'tcx> LateLintPass<'tcx> for Methods {
@@ -1553,6 +1585,7 @@ impl<'tcx> LateLintPass<'tcx> for Methods {
["get_or_insert_with", ..] => unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], "get_or_insert"),
["ok_or_else", ..] => unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], "ok_or"),
["collect", "map"] => lint_map_collect(cx, expr, arg_lists[1], arg_lists[0]),
+ ["for_each", "inspect"] => inspect_for_each::lint(cx, expr, method_spans[1]),
_ => {},
}
diff --git a/tests/ui/inspect_for_each.rs b/tests/ui/inspect_for_each.rs
new file mode 100644
index 00000000000..7fe45c83bca
--- /dev/null
+++ b/tests/ui/inspect_for_each.rs
@@ -0,0 +1,22 @@
+#![warn(clippy::inspect_for_each)]
+
+fn main() {
+ let a: Vec<usize> = vec![1, 2, 3, 4, 5];
+
+ let mut b: Vec<usize> = Vec::new();
+ a.into_iter().inspect(|x| assert!(*x > 0)).for_each(|x| {
+ let y = do_some(x);
+ let z = do_more(y);
+ b.push(z);
+ });
+
+ assert_eq!(b, vec![4, 5, 6, 7, 8]);
+}
+
+fn do_some(a: usize) -> usize {
+ a + 1
+}
+
+fn do_more(a: usize) -> usize {
+ a + 2
+}
diff --git a/tests/ui/inspect_for_each.stderr b/tests/ui/inspect_for_each.stderr
new file mode 100644
index 00000000000..9f976bb7458
--- /dev/null
+++ b/tests/ui/inspect_for_each.stderr
@@ -0,0 +1,16 @@
+error: called `inspect(..).for_each(..)` on an `Iterator`
+ --> $DIR/inspect_for_each.rs:7:19
+ |
+LL | a.into_iter().inspect(|x| assert!(*x > 0)).for_each(|x| {
+ | ___________________^
+LL | | let y = do_some(x);
+LL | | let z = do_more(y);
+LL | | b.push(z);
+LL | | });
+ | |______^
+ |
+ = note: `-D clippy::inspect-for-each` implied by `-D warnings`
+ = help: move the code from `inspect(..)` to `for_each(..)` and remove the `inspect(..)`
+
+error: aborting due to previous error
+