mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-12-22 19:13:29 +00:00
3f62fc3a7e
This is somewhat misleading, as those are actually external crates, and don't need a crate:: prefix.
321 lines
13 KiB
Rust
321 lines
13 KiB
Rust
// Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
|
|
// file at the top-level directory of this distribution.
|
|
//
|
|
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
|
|
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
|
|
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
|
|
// option. This file may not be copied, modified, or distributed
|
|
// except according to those terms.
|
|
|
|
//! Checks for usage of `&Vec[_]` and `&String`.
|
|
|
|
use crate::utils::ptr::get_spans;
|
|
use crate::utils::{match_qpath, match_type, paths, snippet_opt, span_lint, span_lint_and_then, walk_ptrs_hir_ty};
|
|
use if_chain::if_chain;
|
|
use rustc::hir::QPath;
|
|
use rustc::hir::*;
|
|
use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
|
|
use rustc::ty;
|
|
use rustc::{declare_tool_lint, lint_array};
|
|
use rustc_errors::Applicability;
|
|
use std::borrow::Cow;
|
|
use syntax::ast::NodeId;
|
|
use syntax::source_map::Span;
|
|
use syntax_pos::MultiSpan;
|
|
|
|
/// **What it does:** This lint checks for function arguments of type `&String`
|
|
/// or `&Vec` unless the references are mutable. It will also suggest you
|
|
/// replace `.clone()` calls with the appropriate `.to_owned()`/`to_string()`
|
|
/// calls.
|
|
///
|
|
/// **Why is this bad?** Requiring the argument to be of the specific size
|
|
/// makes the function less useful for no benefit; slices in the form of `&[T]`
|
|
/// or `&str` usually suffice and can be obtained from other types, too.
|
|
///
|
|
/// **Known problems:** The lint does not follow data. So if you have an
|
|
/// argument `x` and write `let y = x; y.clone()` the lint will not suggest
|
|
/// changing that `.clone()` to `.to_owned()`.
|
|
///
|
|
/// Other functions called from this function taking a `&String` or `&Vec`
|
|
/// argument may also fail to compile if you change the argument. Applying
|
|
/// this lint on them will fix the problem, but they may be in other crates.
|
|
///
|
|
/// Also there may be `fn(&Vec)`-typed references pointing to your function.
|
|
/// If you have them, you will get a compiler error after applying this lint's
|
|
/// suggestions. You then have the choice to undo your changes or change the
|
|
/// type of the reference.
|
|
///
|
|
/// Note that if the function is part of your public interface, there may be
|
|
/// other crates referencing it you may not be aware. Carefully deprecate the
|
|
/// function before applying the lint suggestions in this case.
|
|
///
|
|
/// **Example:**
|
|
/// ```rust
|
|
/// fn foo(&Vec<u32>) { .. }
|
|
/// ```
|
|
declare_clippy_lint! {
|
|
pub PTR_ARG,
|
|
style,
|
|
"fn arguments of the type `&Vec<...>` or `&String`, suggesting to use `&[...]` or `&str` instead, respectively"
|
|
}
|
|
|
|
/// **What it does:** This lint checks for equality comparisons with `ptr::null`
|
|
///
|
|
/// **Why is this bad?** It's easier and more readable to use the inherent
|
|
/// `.is_null()`
|
|
/// method instead
|
|
///
|
|
/// **Known problems:** None.
|
|
///
|
|
/// **Example:**
|
|
/// ```rust
|
|
/// if x == ptr::null {
|
|
/// ..
|
|
/// }
|
|
/// ```
|
|
declare_clippy_lint! {
|
|
pub CMP_NULL,
|
|
style,
|
|
"comparing a pointer to a null pointer, suggesting to use `.is_null()` instead."
|
|
}
|
|
|
|
/// **What it does:** This lint checks for functions that take immutable
|
|
/// references and return
|
|
/// mutable ones.
|
|
///
|
|
/// **Why is this bad?** This is trivially unsound, as one can create two
|
|
/// mutable references
|
|
/// from the same (immutable!) source. This
|
|
/// [error](https://github.com/rust-lang/rust/issues/39465)
|
|
/// actually lead to an interim Rust release 1.15.1.
|
|
///
|
|
/// **Known problems:** To be on the conservative side, if there's at least one
|
|
/// mutable reference
|
|
/// with the output lifetime, this lint will not trigger. In practice, this
|
|
/// case is unlikely anyway.
|
|
///
|
|
/// **Example:**
|
|
/// ```rust
|
|
/// fn foo(&Foo) -> &mut Bar { .. }
|
|
/// ```
|
|
declare_clippy_lint! {
|
|
pub MUT_FROM_REF,
|
|
correctness,
|
|
"fns that create mutable refs from immutable ref args"
|
|
}
|
|
|
|
#[derive(Copy, Clone)]
|
|
pub struct PointerPass;
|
|
|
|
impl LintPass for PointerPass {
|
|
fn get_lints(&self) -> LintArray {
|
|
lint_array!(PTR_ARG, CMP_NULL, MUT_FROM_REF)
|
|
}
|
|
}
|
|
|
|
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for PointerPass {
|
|
fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
|
|
if let ItemKind::Fn(ref decl, _, _, body_id) = item.node {
|
|
check_fn(cx, decl, item.id, Some(body_id));
|
|
}
|
|
}
|
|
|
|
fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem) {
|
|
if let ImplItemKind::Method(ref sig, body_id) = item.node {
|
|
if let Some(Node::Item(it)) = cx.tcx.hir().find(cx.tcx.hir().get_parent(item.id)) {
|
|
if let ItemKind::Impl(_, _, _, _, Some(_), _, _) = it.node {
|
|
return; // ignore trait impls
|
|
}
|
|
}
|
|
check_fn(cx, &sig.decl, item.id, Some(body_id));
|
|
}
|
|
}
|
|
|
|
fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem) {
|
|
if let TraitItemKind::Method(ref sig, ref trait_method) = item.node {
|
|
let body_id = if let TraitMethod::Provided(b) = *trait_method {
|
|
Some(b)
|
|
} else {
|
|
None
|
|
};
|
|
check_fn(cx, &sig.decl, item.id, body_id);
|
|
}
|
|
}
|
|
|
|
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
|
|
if let ExprKind::Binary(ref op, ref l, ref r) = expr.node {
|
|
if (op.node == BinOpKind::Eq || op.node == BinOpKind::Ne) && (is_null_path(l) || is_null_path(r)) {
|
|
span_lint(
|
|
cx,
|
|
CMP_NULL,
|
|
expr.span,
|
|
"Comparing with null is better expressed by the .is_null() method",
|
|
);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
fn check_fn(cx: &LateContext<'_, '_>, decl: &FnDecl, fn_id: NodeId, opt_body_id: Option<BodyId>) {
|
|
let fn_def_id = cx.tcx.hir().local_def_id(fn_id);
|
|
let sig = cx.tcx.fn_sig(fn_def_id);
|
|
let fn_ty = sig.skip_binder();
|
|
|
|
for (idx, (arg, ty)) in decl.inputs.iter().zip(fn_ty.inputs()).enumerate() {
|
|
if let ty::Ref(_, ty, MutImmutable) = ty.sty {
|
|
if match_type(cx, ty, &paths::VEC) {
|
|
let mut ty_snippet = None;
|
|
if_chain! {
|
|
if let TyKind::Path(QPath::Resolved(_, ref path)) = walk_ptrs_hir_ty(arg).node;
|
|
if let Some(&PathSegment{args: Some(ref parameters), ..}) = path.segments.last();
|
|
then {
|
|
let types: Vec<_> = parameters.args.iter().filter_map(|arg| match arg {
|
|
GenericArg::Type(ty) => Some(ty),
|
|
_ => None,
|
|
}).collect();
|
|
if types.len() == 1 {
|
|
ty_snippet = snippet_opt(cx, types[0].span);
|
|
}
|
|
}
|
|
};
|
|
if let Some(spans) = get_spans(cx, opt_body_id, idx, &[("clone", ".to_owned()")]) {
|
|
span_lint_and_then(
|
|
cx,
|
|
PTR_ARG,
|
|
arg.span,
|
|
"writing `&Vec<_>` instead of `&[_]` involves one more reference and cannot be used \
|
|
with non-Vec-based slices.",
|
|
|db| {
|
|
if let Some(ref snippet) = ty_snippet {
|
|
db.span_suggestion_with_applicability(
|
|
arg.span,
|
|
"change this to",
|
|
format!("&[{}]", snippet),
|
|
Applicability::Unspecified,
|
|
);
|
|
}
|
|
for (clonespan, suggestion) in spans {
|
|
db.span_suggestion_with_applicability(
|
|
clonespan,
|
|
&snippet_opt(cx, clonespan).map_or("change the call to".into(), |x| {
|
|
Cow::Owned(format!("change `{}` to", x))
|
|
}),
|
|
suggestion.into(),
|
|
Applicability::Unspecified,
|
|
);
|
|
}
|
|
},
|
|
);
|
|
}
|
|
} else if match_type(cx, ty, &paths::STRING) {
|
|
if let Some(spans) = get_spans(cx, opt_body_id, idx, &[("clone", ".to_string()"), ("as_str", "")]) {
|
|
span_lint_and_then(
|
|
cx,
|
|
PTR_ARG,
|
|
arg.span,
|
|
"writing `&String` instead of `&str` involves a new object where a slice will do.",
|
|
|db| {
|
|
db.span_suggestion_with_applicability(
|
|
arg.span,
|
|
"change this to",
|
|
"&str".into(),
|
|
Applicability::Unspecified,
|
|
);
|
|
for (clonespan, suggestion) in spans {
|
|
db.span_suggestion_short_with_applicability(
|
|
clonespan,
|
|
&snippet_opt(cx, clonespan).map_or("change the call to".into(), |x| {
|
|
Cow::Owned(format!("change `{}` to", x))
|
|
}),
|
|
suggestion.into(),
|
|
Applicability::Unspecified,
|
|
);
|
|
}
|
|
},
|
|
);
|
|
}
|
|
} else if match_type(cx, ty, &paths::COW) {
|
|
if_chain! {
|
|
if let TyKind::Rptr(_, MutTy { ref ty, ..} ) = arg.node;
|
|
if let TyKind::Path(ref path) = ty.node;
|
|
if let QPath::Resolved(None, ref pp) = *path;
|
|
if let [ref bx] = *pp.segments;
|
|
if let Some(ref params) = bx.args;
|
|
if !params.parenthesized;
|
|
if let Some(inner) = params.args.iter().find_map(|arg| match arg {
|
|
GenericArg::Type(ty) => Some(ty),
|
|
GenericArg::Lifetime(_) => None,
|
|
});
|
|
then {
|
|
let replacement = snippet_opt(cx, inner.span);
|
|
if let Some(r) = replacement {
|
|
span_lint_and_then(
|
|
cx,
|
|
PTR_ARG,
|
|
arg.span,
|
|
"using a reference to `Cow` is not recommended.",
|
|
|db| {
|
|
db.span_suggestion_with_applicability(
|
|
arg.span,
|
|
"change this to",
|
|
"&".to_owned() + &r,
|
|
Applicability::Unspecified,
|
|
);
|
|
},
|
|
);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
if let FunctionRetTy::Return(ref ty) = decl.output {
|
|
if let Some((out, MutMutable, _)) = get_rptr_lm(ty) {
|
|
let mut immutables = vec![];
|
|
for (_, ref mutbl, ref argspan) in decl
|
|
.inputs
|
|
.iter()
|
|
.filter_map(|ty| get_rptr_lm(ty))
|
|
.filter(|&(lt, _, _)| lt.name == out.name)
|
|
{
|
|
if *mutbl == MutMutable {
|
|
return;
|
|
}
|
|
immutables.push(*argspan);
|
|
}
|
|
if immutables.is_empty() {
|
|
return;
|
|
}
|
|
span_lint_and_then(
|
|
cx,
|
|
MUT_FROM_REF,
|
|
ty.span,
|
|
"mutable borrow from immutable input(s)",
|
|
|db| {
|
|
let ms = MultiSpan::from_spans(immutables);
|
|
db.span_note(ms, "immutable borrow here");
|
|
},
|
|
);
|
|
}
|
|
}
|
|
}
|
|
|
|
fn get_rptr_lm(ty: &Ty) -> Option<(&Lifetime, Mutability, Span)> {
|
|
if let TyKind::Rptr(ref lt, ref m) = ty.node {
|
|
Some((lt, m.mutbl, ty.span))
|
|
} else {
|
|
None
|
|
}
|
|
}
|
|
|
|
fn is_null_path(expr: &Expr) -> bool {
|
|
if let ExprKind::Call(ref pathexp, ref args) = expr.node {
|
|
if args.is_empty() {
|
|
if let ExprKind::Path(ref path) = pathexp.node {
|
|
return match_qpath(path, &paths::PTR_NULL) || match_qpath(path, &paths::PTR_NULL_MUT);
|
|
}
|
|
}
|
|
}
|
|
false
|
|
}
|