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use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::is_trait_method;
use clippy_utils::remove_blocks;
use clippy_utils::source::snippet_with_applicability;
use clippy_utils::ty::{is_copy, is_type_diagnostic_item};
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir as hir;
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::mir::Mutability;
use rustc_middle::ty;
use rustc_middle::ty::adjustment::Adjust;
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::symbol::Ident;
use rustc_span::{sym, Span};
declare_clippy_lint! {
/// **What it does:** Checks for usage of `map(|x| x.clone())` or
/// dereferencing closures for `Copy` types, on `Iterator` or `Option`,
/// and suggests `cloned()` or `copied()` instead
///
/// **Why is this bad?** Readability, this can be written more concisely
///
/// **Known problems:** None
///
/// **Example:**
///
/// ```rust
/// let x = vec![42, 43];
/// let y = x.iter();
/// let z = y.map(|i| *i);
/// ```
///
/// The correct use would be:
///
/// ```rust
/// let x = vec![42, 43];
/// let y = x.iter();
/// let z = y.cloned();
/// ```
pub MAP_CLONE,
style,
"using `iterator.map(|x| x.clone())`, or dereferencing closures for `Copy` types"
}
declare_lint_pass!(MapClone => [MAP_CLONE]);
impl<'tcx> LateLintPass<'tcx> for MapClone {
fn check_expr(&mut self, cx: &LateContext<'_>, e: &hir::Expr<'_>) {
if e.span.from_expansion() {
return;
}
if_chain! {
if let hir::ExprKind::MethodCall(method, _, args, _) = e.kind;
if args.len() == 2;
if method.ident.name == sym::map;
let ty = cx.typeck_results().expr_ty(&args[0]);
if is_type_diagnostic_item(cx, ty, sym::option_type) || is_trait_method(cx, e, sym::Iterator);
if let hir::ExprKind::Closure(_, _, body_id, _, _) = args[1].kind;
then {
let closure_body = cx.tcx.hir().body(body_id);
let closure_expr = remove_blocks(&closure_body.value);
match closure_body.params[0].pat.kind {
hir::PatKind::Ref(inner, hir::Mutability::Not) => if let hir::PatKind::Binding(
hir::BindingAnnotation::Unannotated, .., name, None
) = inner.kind {
if ident_eq(name, closure_expr) {
lint(cx, e.span, args[0].span, true);
}
},
hir::PatKind::Binding(hir::BindingAnnotation::Unannotated, .., name, None) => {
match closure_expr.kind {
hir::ExprKind::Unary(hir::UnOp::Deref, inner) => {
if ident_eq(name, inner) {
if let ty::Ref(.., Mutability::Not) = cx.typeck_results().expr_ty(inner).kind() {
lint(cx, e.span, args[0].span, true);
}
}
},
hir::ExprKind::MethodCall(method, _, [obj], _) => if_chain! {
if ident_eq(name, obj) && method.ident.name == sym::clone;
if let Some(fn_id) = cx.typeck_results().type_dependent_def_id(closure_expr.hir_id);
if let Some(trait_id) = cx.tcx.trait_of_item(fn_id);
if cx.tcx.lang_items().clone_trait().map_or(false, |id| id == trait_id);
// no autoderefs
if !cx.typeck_results().expr_adjustments(obj).iter()
.any(|a| matches!(a.kind, Adjust::Deref(Some(..))));
then {
let obj_ty = cx.typeck_results().expr_ty(obj);
if let ty::Ref(_, ty, mutability) = obj_ty.kind() {
if matches!(mutability, Mutability::Not) {
let copy = is_copy(cx, ty);
lint(cx, e.span, args[0].span, copy);
}
} else {
lint_needless_cloning(cx, e.span, args[0].span);
}
}
},
_ => {},
}
},
_ => {},
}
}
}
}
}
fn ident_eq(name: Ident, path: &hir::Expr<'_>) -> bool {
if let hir::ExprKind::Path(hir::QPath::Resolved(None, path)) = path.kind {
path.segments.len() == 1 && path.segments[0].ident == name
} else {
false
}
}
fn lint_needless_cloning(cx: &LateContext<'_>, root: Span, receiver: Span) {
span_lint_and_sugg(
cx,
MAP_CLONE,
root.trim_start(receiver).unwrap(),
"you are needlessly cloning iterator elements",
"remove the `map` call",
String::new(),
Applicability::MachineApplicable,
);
}
fn lint(cx: &LateContext<'_>, replace: Span, root: Span, copied: bool) {
let mut applicability = Applicability::MachineApplicable;
if copied {
span_lint_and_sugg(
cx,
MAP_CLONE,
replace,
"you are using an explicit closure for copying elements",
"consider calling the dedicated `copied` method",
format!(
"{}.copied()",
snippet_with_applicability(cx, root, "..", &mut applicability)
),
applicability,
);
} else {
span_lint_and_sugg(
cx,
MAP_CLONE,
replace,
"you are using an explicit closure for cloning elements",
"consider calling the dedicated `cloned` method",
format!(
"{}.cloned()",
snippet_with_applicability(cx, root, "..", &mut applicability)
),
applicability,
);
}
}
|
