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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; | ||
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declare_clippy_lint! { | ||
/// ### What it does | ||
/// Checks for no-op uses of {Option,Result}::{as_deref,as_deref_mut}. | ||
/// | ||
/// ### Why is this bad? | ||
/// Removes useless code, removing clutter 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 OPTION_NEEDLESS_DEREF, | ||
complexity, | ||
"Explicit use of deref or deref_mut method while not in a method chain." | ||
} | ||
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declare_lint_pass!(OptionNeedlessDeref=> [ | ||
OPTION_NEEDLESS_DEREF, | ||
]); | ||
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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); | ||
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if_chain! { | ||
if is_type_diagnostic_item(cx,outer_ty,sym::option_type) || | ||
is_type_diagnostic_item(cx,outer_ty,sym::result_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{ | ||
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span_lint_and_sugg( | ||
cx, | ||
OPTION_NEEDLESS_DEREF, | ||
expr.span, | ||
"derefed type is same as origin", | ||
"try this", | ||
snippet_opt(cx,sub_expr.span).unwrap(), | ||
Applicability::MachineApplicable | ||
); | ||
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} | ||
} | ||
} | ||
} |
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// run-rustfix | ||
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#[warn(clippy::option_needless_deref)] | ||
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fn main() { | ||
// should lint | ||
let _: Option<&usize> = Some(&1); | ||
let _: Option<&mut usize> = Some(&mut 1); | ||
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// should not lint | ||
let _ = Some(Box::new(1)).as_deref(); | ||
let _ = Some(Box::new(1)).as_deref_mut(); | ||
} |
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// run-rustfix | ||
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#[warn(clippy::option_needless_deref)] | ||
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fn main() { | ||
// should lint | ||
let _: Option<&usize> = Some(&1).as_deref(); | ||
let _: Option<&mut usize> = Some(&mut 1).as_deref_mut(); | ||
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// should not lint | ||
let _ = Some(Box::new(1)).as_deref(); | ||
let _ = Some(Box::new(1)).as_deref_mut(); | ||
} |
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error: derefed type is same as origin | ||
--> $DIR/option_needless_deref.rs:7:29 | ||
| | ||
LL | let _: Option<&usize> = Some(&1).as_deref(); | ||
| ^^^^^^^^^^^^^^^^^^^ help: try this: `Some(&1)` | ||
| | ||
= note: `-D clippy::option-needless-deref` implied by `-D warnings` | ||
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error: derefed type is same as origin | ||
--> $DIR/option_needless_deref.rs:8:33 | ||
| | ||
LL | let _: Option<&mut usize> = Some(&mut 1).as_deref_mut(); | ||
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `Some(&mut 1)` | ||
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error: aborting due to 2 previous errors | ||
|