use rustc::hir::*;
+use rustc::hir::map::*;
use rustc::hir::intravisit::FnKind;
use rustc::lint::*;
use rustc::ty::{self, RegionKind, TypeFoldable};
/// sometimes avoid
/// unnecessary allocations.
///
-/// **Known problems:** Hopefully none.
+/// **Known problems:**
+/// * This lint suggests taking an argument by reference,
+/// however sometimes it is better to let users decide the argument type
+/// (by using `Borrow` trait, for example), depending on how the function is used.
///
/// **Example:**
/// ```rust
/// fn foo(v: Vec<i32>) {
/// assert_eq!(v.len(), 42);
/// }
+/// // should be
+/// fn foo(v: &[i32]) {
+/// assert_eq!(v.len(), 42);
+/// }
/// ```
declare_lint! {
pub NEEDLESS_PASS_BY_VALUE,
match kind {
FnKind::ItemFn(.., attrs) => for a in attrs {
- if_let_chain!{[
- a.meta_item_list().is_some(),
- let Some(name) = a.name(),
- name == "proc_macro_derive",
- ], {
- return;
- }}
+ if_chain! {
+ if a.meta_item_list().is_some();
+ if let Some(name) = a.name();
+ if name == "proc_macro_derive";
+ then {
+ return;
+ }
+ }
},
+ FnKind::Method(..) => (),
_ => return,
}
+ // Exclude non-inherent impls
+ if let Some(NodeItem(item)) = cx.tcx.hir.find(cx.tcx.hir.get_parent_node(node_id)) {
+ if matches!(item.node, ItemImpl(_, _, _, _, Some(_), _, _) | ItemAutoImpl(..)) {
+ return;
+ }
+ }
+
// Allow `Borrow` or functions to be taken by value
let borrow_trait = need!(get_trait_def_id(cx, &paths::BORROW_TRAIT));
let fn_traits = [
let preds = traits::elaborate_predicates(cx.tcx, cx.param_env.caller_bounds.to_vec())
.filter(|p| !p.is_global())
- .filter_map(|pred| if let ty::Predicate::Trait(poly_trait_ref) = pred {
- if poly_trait_ref.def_id() == sized_trait || poly_trait_ref.skip_binder().has_escaping_regions() {
- return None;
+ .filter_map(|pred| {
+ if let ty::Predicate::Trait(poly_trait_ref) = pred {
+ if poly_trait_ref.def_id() == sized_trait || poly_trait_ref.skip_binder().has_escaping_regions() {
+ return None;
+ }
+ Some(poly_trait_ref)
+ } else {
+ None
}
- Some(poly_trait_ref)
- } else {
- None
})
.collect::<Vec<_>>();
} = {
let mut ctx = MovedVariablesCtxt::new(cx);
let region_scope_tree = &cx.tcx.region_scope_tree(fn_def_id);
- euv::ExprUseVisitor::new(&mut ctx, cx.tcx, cx.param_env, region_scope_tree, cx.tables, None).consume_body(body);
+ euv::ExprUseVisitor::new(&mut ctx, cx.tcx, cx.param_env, region_scope_tree, cx.tables, None)
+ .consume_body(body);
ctx
};
return;
}
+ // Ignore `self`s.
+ if idx == 0 {
+ if let PatKind::Binding(_, _, name, ..) = arg.pat.node {
+ if name.node.as_str() == "self" {
+ continue;
+ }
+ }
+ }
+
// * Exclude a type that is specifically bounded by `Borrow`.
// * Exclude a type whose reference also fulfills its bound.
// (e.g. `std::convert::AsRef`, `serde::Serialize`)
)
};
- if_let_chain! {[
- !is_self(arg),
- !ty.is_mutable_pointer(),
- !is_copy(cx, ty),
- !fn_traits.iter().any(|&t| implements_trait(cx, ty, t, &[])),
- !implements_borrow_trait,
- !all_borrowable_trait,
-
- let PatKind::Binding(mode, canonical_id, ..) = arg.pat.node,
- !moved_vars.contains(&canonical_id),
- ], {
- if mode == BindingAnnotation::Mutable || mode == BindingAnnotation::RefMut {
- continue;
- }
+ if_chain! {
+ if !is_self(arg);
+ if !ty.is_mutable_pointer();
+ if !is_copy(cx, ty);
+ if !fn_traits.iter().any(|&t| implements_trait(cx, ty, t, &[]));
+ if !implements_borrow_trait;
+ if !all_borrowable_trait;
+
+ if let PatKind::Binding(mode, canonical_id, ..) = arg.pat.node;
+ if !moved_vars.contains(&canonical_id);
+ then {
+ if mode == BindingAnnotation::Mutable || mode == BindingAnnotation::RefMut {
+ continue;
+ }
- // Dereference suggestion
- let sugg = |db: &mut DiagnosticBuilder| {
- let deref_span = spans_need_deref.get(&canonical_id);
- if_let_chain! {[
- match_type(cx, ty, &paths::VEC),
- let Some(clone_spans) =
- get_spans(cx, Some(body.id()), idx, &[("clone", ".to_owned()")]),
- let TyPath(QPath::Resolved(_, ref path)) = input.node,
- let Some(elem_ty) = path.segments.iter()
- .find(|seg| seg.name == "Vec")
- .and_then(|ps| ps.parameters.as_ref())
- .map(|params| ¶ms.types[0]),
- ], {
- let slice_ty = format!("&[{}]", snippet(cx, elem_ty.span, "_"));
- db.span_suggestion(input.span,
- "consider changing the type to",
- slice_ty);
-
- for (span, suggestion) in clone_spans {
- db.span_suggestion(
- span,
- &snippet_opt(cx, span)
- .map_or(
- "change the call to".into(),
- |x| Cow::from(format!("change `{}` to", x)),
- ),
- suggestion.into()
- );
+ // Dereference suggestion
+ let sugg = |db: &mut DiagnosticBuilder| {
+ let deref_span = spans_need_deref.get(&canonical_id);
+ if_chain! {
+ if match_type(cx, ty, &paths::VEC);
+ if let Some(clone_spans) =
+ get_spans(cx, Some(body.id()), idx, &[("clone", ".to_owned()")]);
+ if let TyPath(QPath::Resolved(_, ref path)) = input.node;
+ if let Some(elem_ty) = path.segments.iter()
+ .find(|seg| seg.name == "Vec")
+ .and_then(|ps| ps.parameters.as_ref())
+ .map(|params| ¶ms.types[0]);
+ then {
+ let slice_ty = format!("&[{}]", snippet(cx, elem_ty.span, "_"));
+ db.span_suggestion(input.span,
+ "consider changing the type to",
+ slice_ty);
+
+ for (span, suggestion) in clone_spans {
+ db.span_suggestion(
+ span,
+ &snippet_opt(cx, span)
+ .map_or(
+ "change the call to".into(),
+ |x| Cow::from(format!("change `{}` to", x)),
+ ),
+ suggestion.into()
+ );
+ }
+
+ // cannot be destructured, no need for `*` suggestion
+ assert!(deref_span.is_none());
+ return;
+ }
}
- // cannot be destructured, no need for `*` suggestion
- assert!(deref_span.is_none());
- return;
- }}
-
- if match_type(cx, ty, &paths::STRING) {
- if let Some(clone_spans) =
- get_spans(cx, Some(body.id()), idx, &[("clone", ".to_string()"), ("as_str", "")]) {
- db.span_suggestion(input.span, "consider changing the type to", "&str".to_string());
-
- for (span, suggestion) in clone_spans {
- db.span_suggestion(
- span,
- &snippet_opt(cx, span)
- .map_or(
- "change the call to".into(),
- |x| Cow::from(format!("change `{}` to", x))
- ),
- suggestion.into(),
- );
+ if match_type(cx, ty, &paths::STRING) {
+ if let Some(clone_spans) =
+ get_spans(cx, Some(body.id()), idx, &[("clone", ".to_string()"), ("as_str", "")]) {
+ db.span_suggestion(input.span, "consider changing the type to", "&str".to_string());
+
+ for (span, suggestion) in clone_spans {
+ db.span_suggestion(
+ span,
+ &snippet_opt(cx, span)
+ .map_or(
+ "change the call to".into(),
+ |x| Cow::from(format!("change `{}` to", x))
+ ),
+ suggestion.into(),
+ );
+ }
+
+ assert!(deref_span.is_none());
+ return;
}
-
- assert!(deref_span.is_none());
- return;
}
- }
- let mut spans = vec![(input.span, format!("&{}", snippet(cx, input.span, "_")))];
-
- // Suggests adding `*` to dereference the added reference.
- if let Some(deref_span) = deref_span {
- spans.extend(
- deref_span
- .iter()
- .cloned()
- .map(|span| (span, format!("*{}", snippet(cx, span, "<expr>")))),
- );
- spans.sort_by_key(|&(span, _)| span);
- }
- multispan_sugg(db, "consider taking a reference instead".to_string(), spans);
- };
-
- span_lint_and_then(
- cx,
- NEEDLESS_PASS_BY_VALUE,
- input.span,
- "this argument is passed by value, but not consumed in the function body",
- sugg,
- );
- }}
+ let mut spans = vec![(input.span, format!("&{}", snippet(cx, input.span, "_")))];
+
+ // Suggests adding `*` to dereference the added reference.
+ if let Some(deref_span) = deref_span {
+ spans.extend(
+ deref_span
+ .iter()
+ .cloned()
+ .map(|span| (span, format!("*{}", snippet(cx, span, "<expr>")))),
+ );
+ spans.sort_by_key(|&(span, _)| span);
+ }
+ multispan_sugg(db, "consider taking a reference instead".to_string(), spans);
+ };
+
+ span_lint_and_then(
+ cx,
+ NEEDLESS_PASS_BY_VALUE,
+ input.span,
+ "this argument is passed by value, but not consumed in the function body",
+ sugg,
+ );
+ }
+ }
}
}
}
map::Node::NodeStmt(s) => {
// `let <pat> = x;`
- if_let_chain! {[
- let StmtDecl(ref decl, _) = s.node,
- let DeclLocal(ref local) = decl.node,
- ], {
- self.spans_need_deref
- .entry(vid)
- .or_insert_with(HashSet::new)
- .insert(local.init
- .as_ref()
- .map(|e| e.span)
- .expect("`let` stmt without init aren't caught by match_pat"));
- }}
+ if_chain! {
+ if let StmtDecl(ref decl, _) = s.node;
+ if let DeclLocal(ref local) = decl.node;
+ then {
+ self.spans_need_deref
+ .entry(vid)
+ .or_insert_with(HashSet::new)
+ .insert(local.init
+ .as_ref()
+ .map(|e| e.span)
+ .expect("`let` stmt without init aren't caught by match_pat"));
+ }
+ }
},
_ => {},
projects / rust.git / blobdiff