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option_needless_deref
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‎CHANGELOG.md

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@@ -2848,6 +2848,7 @@ Released 2018-09-13
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[`option_if_let_else`]: https://rust-lang.github.io/rust-clippy/master/index.html#option_if_let_else
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[`option_map_or_none`]: https://rust-lang.github.io/rust-clippy/master/index.html#option_map_or_none
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[`option_map_unit_fn`]: https://rust-lang.github.io/rust-clippy/master/index.html#option_map_unit_fn
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[`option_needless_deref`]: https://rust-lang.github.io/rust-clippy/master/index.html#option_needless_deref
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[`option_option`]: https://rust-lang.github.io/rust-clippy/master/index.html#option_option
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[`or_fun_call`]: https://rust-lang.github.io/rust-clippy/master/index.html#or_fun_call
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[`out_of_bounds_indexing`]: https://rust-lang.github.io/rust-clippy/master/index.html#out_of_bounds_indexing

‎clippy_lints/src/lib.rs

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@@ -304,6 +304,7 @@ mod nonstandard_macro_braces;
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mod open_options;
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mod option_env_unwrap;
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mod option_if_let_else;
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mod option_needless_deref;
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mod overflow_check_conditional;
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mod panic_in_result_fn;
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mod panic_unimplemented;
@@ -865,6 +866,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
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open_options::NONSENSICAL_OPEN_OPTIONS,
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option_env_unwrap::OPTION_ENV_UNWRAP,
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option_if_let_else::OPTION_IF_LET_ELSE,
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option_needless_deref::OPTION_NEEDLESS_DEREF,
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overflow_check_conditional::OVERFLOW_CHECK_CONDITIONAL,
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panic_in_result_fn::PANIC_IN_RESULT_FN,
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panic_unimplemented::PANIC,
@@ -1387,6 +1389,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
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LintId::of(non_octal_unix_permissions::NON_OCTAL_UNIX_PERMISSIONS),
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LintId::of(open_options::NONSENSICAL_OPEN_OPTIONS),
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LintId::of(option_env_unwrap::OPTION_ENV_UNWRAP),
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LintId::of(option_needless_deref::OPTION_NEEDLESS_DEREF),
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LintId::of(overflow_check_conditional::OVERFLOW_CHECK_CONDITIONAL),
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LintId::of(partialeq_ne_impl::PARTIALEQ_NE_IMPL),
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LintId::of(precedence::PRECEDENCE),
@@ -1640,6 +1643,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
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LintId::of(neg_cmp_op_on_partial_ord::NEG_CMP_OP_ON_PARTIAL_ORD),
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LintId::of(no_effect::NO_EFFECT),
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LintId::of(no_effect::UNNECESSARY_OPERATION),
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LintId::of(option_needless_deref::OPTION_NEEDLESS_DEREF),
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LintId::of(overflow_check_conditional::OVERFLOW_CHECK_CONDITIONAL),
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LintId::of(partialeq_ne_impl::PARTIALEQ_NE_IMPL),
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LintId::of(precedence::PRECEDENCE),
@@ -1863,6 +1867,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
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store.register_late_pass(|| box ptr::Ptr);
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store.register_late_pass(|| box ptr_eq::PtrEq);
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store.register_late_pass(|| box needless_bool::NeedlessBool);
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store.register_late_pass(|| box option_needless_deref::OptionNeedlessDeref);
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store.register_late_pass(|| box needless_bool::BoolComparison);
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store.register_late_pass(|| box needless_for_each::NeedlessForEach);
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store.register_late_pass(|| box approx_const::ApproxConstant);

‎clippy_lints/src/loops/never_loop.rs

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@@ -87,7 +87,7 @@ fn combine_branches(b1: NeverLoopResult, b2: NeverLoopResult) -> NeverLoopResult
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fn never_loop_block(block: &Block<'_>, main_loop_id: HirId) -> NeverLoopResult {
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let stmts = block.stmts.iter().map(stmt_to_expr);
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let expr = once(block.expr.as_deref());
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let expr = once(block.expr);
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let mut iter = stmts.chain(expr).flatten();
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never_loop_expr_seq(&mut iter, main_loop_id)
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}
@@ -100,7 +100,7 @@ fn never_loop_expr_seq<'a, T: Iterator<Item = &'a Expr<'a>>>(es: &mut T, main_lo
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fn stmt_to_expr<'tcx>(stmt: &Stmt<'tcx>) -> Option<&'tcx Expr<'tcx>> {
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match stmt.kind {
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StmtKind::Semi(e, ..) | StmtKind::Expr(e, ..) => Some(e),
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StmtKind::Local(local) => local.init.as_deref(),
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StmtKind::Local(local) => local.init,
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StmtKind::Item(..) => None,
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}
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}

‎clippy_lints/src/option_needless_deref.rs

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@@ -0,0 +1,71 @@
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use clippy_utils::diagnostics::span_lint_and_sugg;
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use clippy_utils::in_macro;
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use clippy_utils::source::snippet_opt;
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use clippy_utils::ty::is_type_diagnostic_item;
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use rustc_errors::Applicability;
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use rustc_hir::{Expr, ExprKind};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_middle::ty::TyS;
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use rustc_span::symbol::sym;
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for no-op uses of {Option,Result}::{as_deref,as_deref_mut}.
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///
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/// ### Why is this bad?
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/// Removes useless code, removing clutter and improving readability.
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///
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/// ### Example
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/// ```rust
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/// let a = Some(&1);
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/// let b = a.as_deref(); // goes from Option<&i32> to Option<&i32>
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/// ```
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/// Could be written as:
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/// ```rust
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/// let a = Some(&1);
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/// let b = a;
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/// ```
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pub OPTION_NEEDLESS_DEREF,
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complexity,
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"Explicit use of deref or deref_mut method while not in a method chain."
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}
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declare_lint_pass!(OptionNeedlessDeref=> [
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OPTION_NEEDLESS_DEREF,
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]);
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impl<'tcx> LateLintPass<'tcx> for OptionNeedlessDeref {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
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if expr.span.from_expansion() {
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return;
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}
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if in_macro(expr.span) {
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return;
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}
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let typeck = cx.typeck_results();
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let outer_ty = typeck.expr_ty(expr);
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if_chain! {
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if is_type_diagnostic_item(cx,outer_ty,sym::option_type) ||
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is_type_diagnostic_item(cx,outer_ty,sym::result_type) ;
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if let ExprKind::MethodCall(path, _, [sub_expr], _) = expr.kind;
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let symbol = &*path.ident.as_str();
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if symbol=="as_deref" || symbol=="as_deref_mut";
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if TyS::same_type( outer_ty, typeck.expr_ty(sub_expr) );
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then{
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span_lint_and_sugg(
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cx,
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OPTION_NEEDLESS_DEREF,
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expr.span,
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"derefed type is same as origin",
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"try this",
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snippet_opt(cx,sub_expr.span).unwrap(),
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Applicability::MachineApplicable
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);
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}
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}
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}
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}

‎tests/ui/option_needless_deref.fixed

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// run-rustfix
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#[warn(clippy::option_needless_deref)]
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fn main() {
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// should lint
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let _: Option<&usize> = Some(&1);
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let _: Option<&mut usize> = Some(&mut 1);
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// should not lint
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let _ = Some(Box::new(1)).as_deref();
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let _ = Some(Box::new(1)).as_deref_mut();
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}

‎tests/ui/option_needless_deref.rs

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// run-rustfix
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#[warn(clippy::option_needless_deref)]
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fn main() {
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// should lint
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let _: Option<&usize> = Some(&1).as_deref();
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let _: Option<&mut usize> = Some(&mut 1).as_deref_mut();
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// should not lint
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let _ = Some(Box::new(1)).as_deref();
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let _ = Some(Box::new(1)).as_deref_mut();
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}

‎tests/ui/option_needless_deref.stderr

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error: derefed type is same as origin
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--> $DIR/option_needless_deref.rs:7:29
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|
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LL | let _: Option<&usize> = Some(&1).as_deref();
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| ^^^^^^^^^^^^^^^^^^^ help: try this: `Some(&1)`
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|
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= note: `-D clippy::option-needless-deref` implied by `-D warnings`
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error: derefed type is same as origin
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--> $DIR/option_needless_deref.rs:8:33
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|
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LL | let _: Option<&mut usize> = Some(&mut 1).as_deref_mut();
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `Some(&mut 1)`
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error: aborting due to 2 previous errors
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