//! Checks for usage of `&Vec[_]` and `&String`.
+use std::borrow::Cow;
use rustc::hir::*;
use rustc::hir::map::NodeItem;
+use rustc::hir::QPath;
use rustc::lint::*;
use rustc::ty;
use syntax::ast::NodeId;
-use utils::{match_path, match_type, paths, span_lint};
+use syntax::codemap::Span;
+use syntax_pos::MultiSpan;
+use crate::utils::{match_qpath, match_type, paths, snippet_opt, span_lint, span_lint_and_then, walk_ptrs_hir_ty};
+use crate::utils::ptr::get_spans;
-/// **What it does:** This lint checks for function arguments of type `&String` or `&Vec` unless
-/// the references are mutable.
+/// **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.
+/// **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:** None.
+/// **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_lint! {
+declare_clippy_lint! {
pub PTR_ARG,
- Warn,
+ 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()`
+/// **Why is this bad?** It's easier and more readable to use the inherent
+/// `.is_null()`
/// method instead
///
/// **Known problems:** None.
/// ```rust
/// if x == ptr::null { .. }
/// ```
-declare_lint! {
+declare_clippy_lint! {
pub CMP_NULL,
- Warn,
+ 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)]
+#[derive(Copy, Clone)]
pub struct PointerPass;
impl LintPass for PointerPass {
fn get_lints(&self) -> LintArray {
- lint_array!(PTR_ARG, CMP_NULL)
+ 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 ItemFn(ref decl, _, _, _, _, _) = item.node {
- check_fn(cx, decl, item.id);
+ if let ItemFn(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, _) = item.node {
- if let Some(NodeItem(it)) = cx.tcx.map.find(cx.tcx.map.get_parent(item.id)) {
- if let ItemImpl(_, _, _, Some(_), _, _) = it.node {
+ if let ImplItemKind::Method(ref sig, body_id) = item.node {
+ if let Some(NodeItem(it)) = cx.tcx.hir.find(cx.tcx.hir.get_parent(item.id)) {
+ if let ItemImpl(_, _, _, _, Some(_), _, _) = it.node {
return; // ignore trait impls
}
}
- check_fn(cx, &sig.decl, item.id);
+ 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 MethodTraitItem(ref sig, _) = item.node {
- check_fn(cx, &sig.decl, item.id);
+ 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 ExprBinary(ref op, ref l, ref r) = expr.node {
- if (op.node == BiEq || op.node == BiNe) && (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");
+ 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) {
- let fn_def_id = cx.tcx.map.local_def_id(fn_id);
- let fn_ty = cx.tcx.item_type(fn_def_id).fn_sig().skip_binder();
+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 (arg, ty) in decl.inputs.iter().zip(fn_ty.inputs()) {
- if let ty::TyRef(_, ty::TypeAndMut { ty, mutbl: MutImmutable }) = ty.sty {
+ for (idx, (arg, ty)) in decl.inputs.iter().zip(fn_ty.inputs()).enumerate() {
+ if let ty::TyRef(
+ _,
+ ty,
+ MutImmutable
+ ) = ty.sty
+ {
if match_type(cx, ty, &paths::VEC) {
- span_lint(cx,
- PTR_ARG,
- arg.ty.span,
- "writing `&Vec<_>` instead of `&[_]` involves one more reference and cannot be used \
- with non-Vec-based slices. Consider changing the type to `&[...]`");
+ let mut ty_snippet = None;
+ if_chain! {
+ if let TyPath(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(arg.span, "change this to", format!("&[{}]", snippet));
+ }
+ for (clonespan, suggestion) in spans {
+ db.span_suggestion(
+ clonespan,
+ &snippet_opt(cx, clonespan).map_or(
+ "change the call to".into(),
+ |x| Cow::Owned(format!("change `{}` to", x)),
+ ),
+ suggestion.into(),
+ );
+ }
+ },
+ );
+ }
} else if match_type(cx, ty, &paths::STRING) {
- span_lint(cx,
- PTR_ARG,
- arg.ty.span,
- "writing `&String` instead of `&str` involves a new object where a slice will do. \
- Consider changing the type to `&str`");
+ 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(arg.span, "change this to", "&str".into());
+ for (clonespan, suggestion) in spans {
+ db.span_suggestion_short(
+ clonespan,
+ &snippet_opt(cx, clonespan).map_or(
+ "change the call to".into(),
+ |x| Cow::Owned(format!("change `{}` to", x)),
+ ),
+ suggestion.into(),
+ );
+ }
+ },
+ );
+ }
+ } else if match_type(cx, ty, &paths::COW) {
+ if_chain! {
+ if let TyRptr(_, MutTy { ref ty, ..} ) = arg.node;
+ if let TyPath(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(arg.span, "change this to", "&".to_owned() + &r);
+ },
+ );
+ }
+ }
+ }
}
}
}
+
+ 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 Ty_::TyRptr(ref lt, ref m) = ty.node {
+ Some((lt, m.mutbl, ty.span))
+ } else {
+ None
+ }
}
fn is_null_path(expr: &Expr) -> bool {
- if let ExprCall(ref pathexp, ref args) = expr.node {
+ if let ExprKind::Call(ref pathexp, ref args) = expr.node {
if args.is_empty() {
- if let ExprPath(ref path) = pathexp.node {
- return match_path(path, &paths::PTR_NULL) || match_path(path, &paths::PTR_NULL_MUT);
+ if let ExprKind::Path(ref path) = pathexp.node {
+ return match_qpath(path, &paths::PTR_NULL) || match_qpath(path, &paths::PTR_NULL_MUT);
}
}
}
projects / rust.git / blobdiff