diff --git a/CHANGELOG.md b/CHANGELOG.md
index d86414a87f4..0e131ed02af 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2822,6 +2822,7 @@ Released 2018-09-13
[`needless_doctest_main`]: https://rust-lang.github.io/rust-clippy/master/index.html#needless_doctest_main
[`needless_for_each`]: https://rust-lang.github.io/rust-clippy/master/index.html#needless_for_each
[`needless_lifetimes`]: https://rust-lang.github.io/rust-clippy/master/index.html#needless_lifetimes
+[`needless_option_as_deref`]: https://rust-lang.github.io/rust-clippy/master/index.html#needless_option_as_deref
[`needless_pass_by_value`]: https://rust-lang.github.io/rust-clippy/master/index.html#needless_pass_by_value
[`needless_question_mark`]: https://rust-lang.github.io/rust-clippy/master/index.html#needless_question_mark
[`needless_range_loop`]: https://rust-lang.github.io/rust-clippy/master/index.html#needless_range_loop
diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs
index 2b76eacb7d6..64b7ff199be 100644
--- a/clippy_lints/src/lib.rs
+++ b/clippy_lints/src/lib.rs
@@ -289,6 +289,7 @@ mod needless_borrow;
mod needless_borrowed_ref;
mod needless_continue;
mod needless_for_each;
+mod needless_option_as_deref;
mod needless_pass_by_value;
mod needless_question_mark;
mod needless_update;
@@ -847,6 +848,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
needless_borrowed_ref::NEEDLESS_BORROWED_REFERENCE,
needless_continue::NEEDLESS_CONTINUE,
needless_for_each::NEEDLESS_FOR_EACH,
+ needless_option_as_deref::NEEDLESS_OPTION_AS_DEREF,
needless_pass_by_value::NEEDLESS_PASS_BY_VALUE,
needless_question_mark::NEEDLESS_QUESTION_MARK,
needless_update::NEEDLESS_UPDATE,
@@ -1374,6 +1376,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
LintId::of(needless_bool::NEEDLESS_BOOL),
LintId::of(needless_borrow::NEEDLESS_BORROW),
LintId::of(needless_borrowed_ref::NEEDLESS_BORROWED_REFERENCE),
+ LintId::of(needless_option_as_deref::NEEDLESS_OPTION_AS_DEREF),
LintId::of(needless_question_mark::NEEDLESS_QUESTION_MARK),
LintId::of(needless_update::NEEDLESS_UPDATE),
LintId::of(neg_cmp_op_on_partial_ord::NEG_CMP_OP_ON_PARTIAL_ORD),
@@ -1636,6 +1639,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
LintId::of(needless_bool::BOOL_COMPARISON),
LintId::of(needless_bool::NEEDLESS_BOOL),
LintId::of(needless_borrowed_ref::NEEDLESS_BORROWED_REFERENCE),
+ LintId::of(needless_option_as_deref::NEEDLESS_OPTION_AS_DEREF),
LintId::of(needless_question_mark::NEEDLESS_QUESTION_MARK),
LintId::of(needless_update::NEEDLESS_UPDATE),
LintId::of(neg_cmp_op_on_partial_ord::NEG_CMP_OP_ON_PARTIAL_ORD),
@@ -1863,6 +1867,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
store.register_late_pass(|| Box::new(ptr::Ptr));
store.register_late_pass(|| Box::new(ptr_eq::PtrEq));
store.register_late_pass(|| Box::new(needless_bool::NeedlessBool));
+ store.register_late_pass(|| Box::new(needless_option_as_deref::OptionNeedlessDeref));
store.register_late_pass(|| Box::new(needless_bool::BoolComparison));
store.register_late_pass(|| Box::new(needless_for_each::NeedlessForEach));
store.register_late_pass(|| Box::new(approx_const::ApproxConstant));
diff --git a/clippy_lints/src/loops/never_loop.rs b/clippy_lints/src/loops/never_loop.rs
index 2c46971d5f7..41956650c9f 100644
--- a/clippy_lints/src/loops/never_loop.rs
+++ b/clippy_lints/src/loops/never_loop.rs
@@ -87,7 +87,7 @@ fn combine_branches(b1: NeverLoopResult, b2: NeverLoopResult) -> NeverLoopResult
fn never_loop_block(block: &Block<'_>, main_loop_id: HirId) -> NeverLoopResult {
let stmts = block.stmts.iter().map(stmt_to_expr);
- let expr = once(block.expr.as_deref());
+ let expr = once(block.expr);
let mut iter = stmts.chain(expr).flatten();
never_loop_expr_seq(&mut iter, main_loop_id)
}
@@ -100,7 +100,7 @@ fn never_loop_expr_seq<'a, T: Iterator<Item = &'a Expr<'a>>>(es: &mut T, main_lo
fn stmt_to_expr<'tcx>(stmt: &Stmt<'tcx>) -> Option<&'tcx Expr<'tcx>> {
match stmt.kind {
StmtKind::Semi(e, ..) | StmtKind::Expr(e, ..) => Some(e),
- StmtKind::Local(local) => local.init.as_deref(),
+ StmtKind::Local(local) => local.init,
StmtKind::Item(..) => None,
}
}
diff --git a/clippy_lints/src/needless_option_as_deref.rs b/clippy_lints/src/needless_option_as_deref.rs
new file mode 100644
index 00000000000..67c697da04f
--- /dev/null
+++ b/clippy_lints/src/needless_option_as_deref.rs
@@ -0,0 +1,69 @@
+use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::in_macro;
+use clippy_utils::source::snippet_opt;
+use clippy_utils::ty::is_type_diagnostic_item;
+use rustc_errors::Applicability;
+use rustc_hir::{Expr, ExprKind};
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_middle::ty::TyS;
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::symbol::sym;
+
+declare_clippy_lint! {
+ /// ### What it does
+ /// Checks for no-op uses of Option::{as_deref,as_deref_mut},
+ /// for example, `Option<&T>::as_deref()` returns the same type.
+ ///
+ /// ### Why is this bad?
+ /// Redundant code and improving readability.
+ ///
+ /// ### Example
+ /// ```rust
+ /// let a = Some(&1);
+ /// let b = a.as_deref(); // goes from Option<&i32> to Option<&i32>
+ /// ```
+ /// Could be written as:
+ /// ```rust
+ /// let a = Some(&1);
+ /// let b = a;
+ /// ```
+ pub NEEDLESS_OPTION_AS_DEREF,
+ complexity,
+ "no-op use of `deref` or `deref_mut` method to `Option`."
+}
+
+declare_lint_pass!(OptionNeedlessDeref=> [
+ NEEDLESS_OPTION_AS_DEREF,
+]);
+
+impl<'tcx> LateLintPass<'tcx> for OptionNeedlessDeref {
+ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
+ if expr.span.from_expansion() {
+ return;
+ }
+ if in_macro(expr.span) {
+ return;
+ }
+ let typeck = cx.typeck_results();
+ let outer_ty = typeck.expr_ty(expr);
+
+ if_chain! {
+ if is_type_diagnostic_item(cx,outer_ty,sym::option_type);
+ if let ExprKind::MethodCall(path, _, [sub_expr], _) = expr.kind;
+ let symbol = path.ident.as_str();
+ if symbol=="as_deref" || symbol=="as_deref_mut";
+ if TyS::same_type( outer_ty, typeck.expr_ty(sub_expr) );
+ then{
+ span_lint_and_sugg(
+ cx,
+ NEEDLESS_OPTION_AS_DEREF,
+ expr.span,
+ "derefed type is same as origin",
+ "try this",
+ snippet_opt(cx,sub_expr.span).unwrap(),
+ Applicability::MachineApplicable
+ );
+ }
+ }
+ }
+}
diff --git a/tests/ui/needless_option_as_deref.fixed b/tests/ui/needless_option_as_deref.fixed
new file mode 100644
index 00000000000..d721452ae88
--- /dev/null
+++ b/tests/ui/needless_option_as_deref.fixed
@@ -0,0 +1,13 @@
+// run-rustfix
+
+#[warn(clippy::needless_option_as_deref)]
+
+fn main() {
+ // should lint
+ let _: Option<&usize> = Some(&1);
+ let _: Option<&mut usize> = Some(&mut 1);
+
+ // should not lint
+ let _ = Some(Box::new(1)).as_deref();
+ let _ = Some(Box::new(1)).as_deref_mut();
+}
diff --git a/tests/ui/needless_option_as_deref.rs b/tests/ui/needless_option_as_deref.rs
new file mode 100644
index 00000000000..bb15512adf6
--- /dev/null
+++ b/tests/ui/needless_option_as_deref.rs
@@ -0,0 +1,13 @@
+// run-rustfix
+
+#[warn(clippy::needless_option_as_deref)]
+
+fn main() {
+ // should lint
+ let _: Option<&usize> = Some(&1).as_deref();
+ let _: Option<&mut usize> = Some(&mut 1).as_deref_mut();
+
+ // should not lint
+ let _ = Some(Box::new(1)).as_deref();
+ let _ = Some(Box::new(1)).as_deref_mut();
+}
diff --git a/tests/ui/needless_option_as_deref.stderr b/tests/ui/needless_option_as_deref.stderr
new file mode 100644
index 00000000000..5dd507b4a71
--- /dev/null
+++ b/tests/ui/needless_option_as_deref.stderr
@@ -0,0 +1,16 @@
+error: derefed type is same as origin
+ --> $DIR/needless_option_as_deref.rs:7:29
+ |
+LL | let _: Option<&usize> = Some(&1).as_deref();
+ | ^^^^^^^^^^^^^^^^^^^ help: try this: `Some(&1)`
+ |
+ = note: `-D clippy::needless-option-as-deref` implied by `-D warnings`
+
+error: derefed type is same as origin
+ --> $DIR/needless_option_as_deref.rs:8:33
+ |
+LL | let _: Option<&mut usize> = Some(&mut 1).as_deref_mut();
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `Some(&mut 1)`
+
+error: aborting due to 2 previous errors
+