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rust-clippy/src/methods.rs
mcarton 8e9e858b78 Remove uses of ast_ty_to_ty_cache
2016-03-08 17:00:44 +01:00

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use rustc::lint::*;
use rustc::middle::const_eval::EvalHint::ExprTypeChecked;
use rustc::middle::const_eval::{ConstVal, eval_const_expr_partial};
use rustc::middle::cstore::CrateStore;
use rustc::middle::subst::{Subst, TypeSpace};
use rustc::middle::ty;
use rustc_front::hir::*;
use std::borrow::Cow;
use std::{fmt, iter};
use syntax::codemap::Span;
use syntax::ptr::P;
use utils::{get_trait_def_id, implements_trait, in_external_macro, in_macro, match_path, match_trait_method,
match_type, method_chain_args, return_ty, snippet, snippet_opt, span_lint,
span_lint_and_then, span_note_and_lint, walk_ptrs_ty, walk_ptrs_ty_depth};
use utils::{BTREEMAP_ENTRY_PATH, DEFAULT_TRAIT_PATH, HASHMAP_ENTRY_PATH, OPTION_PATH, RESULT_PATH, STRING_PATH,
VEC_PATH};
use utils::MethodArgs;
#[derive(Clone)]
pub struct MethodsPass;
/// **What it does:** This lint checks for `.unwrap()` calls on `Option`s.
///
/// **Why is this bad?** Usually it is better to handle the `None` case, or to at least call `.expect(_)` with a more helpful message. Still, for a lot of quick-and-dirty code, `unwrap` is a good choice, which is why this lint is `Allow` by default.
///
/// **Known problems:** None
///
/// **Example:** `x.unwrap()`
declare_lint! {
pub OPTION_UNWRAP_USED, Allow,
"using `Option.unwrap()`, which should at least get a better message using `expect()`"
}
/// **What it does:** This lint checks for `.unwrap()` calls on `Result`s.
///
/// **Why is this bad?** `result.unwrap()` will let the thread panic on `Err` values. Normally, you want to implement more sophisticated error handling, and propagate errors upwards with `try!`.
///
/// Even if you want to panic on errors, not all `Error`s implement good messages on display. Therefore it may be beneficial to look at the places where they may get displayed. Activate this lint to do just that.
///
/// **Known problems:** None
///
/// **Example:** `x.unwrap()`
declare_lint! {
pub RESULT_UNWRAP_USED, Allow,
"using `Result.unwrap()`, which might be better handled"
}
/// **What it does:** This lint checks for `.to_string()` method calls on values of type `&str`.
///
/// **Why is this bad?** This uses the whole formatting machinery just to clone a string. Using `.to_owned()` is lighter on resources. You can also consider using a [`Cow<'a, str>`](http://doc.rust-lang.org/std/borrow/enum.Cow.html) instead in some cases.
///
/// **Known problems:** None
///
/// **Example:** `s.to_string()` where `s: &str`
declare_lint! {
pub STR_TO_STRING, Warn,
"using `to_string()` on a str, which should be `to_owned()`"
}
/// **What it does:** This lint checks for `.to_string()` method calls on values of type `String`.
///
/// **Why is this bad?** This is an non-efficient way to clone a `String`, `.clone()` should be used
/// instead. `String` implements `ToString` mostly for generics.
///
/// **Known problems:** None
///
/// **Example:** `s.to_string()` where `s: String`
declare_lint! {
pub STRING_TO_STRING, Warn,
"calling `String::to_string` which is inefficient"
}
/// **What it does:** This lint checks for methods that should live in a trait implementation of a `std` trait (see [llogiq's blog post](http://llogiq.github.io/2015/07/30/traits.html) for further information) instead of an inherent implementation.
///
/// **Why is this bad?** Implementing the traits improve ergonomics for users of the code, often with very little cost. Also people seeing a `mul(..)` method may expect `*` to work equally, so you should have good reason to disappoint them.
///
/// **Known problems:** None
///
/// **Example:**
/// ```
/// struct X;
/// impl X {
/// fn add(&self, other: &X) -> X { .. }
/// }
/// ```
declare_lint! {
pub SHOULD_IMPLEMENT_TRAIT, Warn,
"defining a method that should be implementing a std trait"
}
/// **What it does:** This lint checks for methods with certain name prefixes and which doesn't match how self is taken. The actual rules are:
///
/// |Prefix |`self` taken |
/// |-------|--------------------|
/// |`as_` |`&self` or &mut self|
/// |`from_`| none |
/// |`into_`|`self` |
/// |`is_` |`&self` or none |
/// |`to_` |`&self` |
///
/// **Why is this bad?** Consistency breeds readability. If you follow the conventions, your users won't be surprised that they e.g. need to supply a mutable reference to a `as_..` function.
///
/// **Known problems:** None
///
/// **Example**
///
/// ```
/// impl X {
/// fn as_str(self) -> &str { .. }
/// }
/// ```
declare_lint! {
pub WRONG_SELF_CONVENTION, Warn,
"defining a method named with an established prefix (like \"into_\") that takes \
`self` with the wrong convention"
}
/// **What it does:** This is the same as [`wrong_self_convention`](#wrong_self_convention), but for public items.
///
/// **Why is this bad?** See [`wrong_self_convention`](#wrong_self_convention).
///
/// **Known problems:** Actually *renaming* the function may break clients if the function is part of the public interface. In that case, be mindful of the stability guarantees you've given your users.
///
/// **Example:**
/// ```
/// impl X {
/// pub fn as_str(self) -> &str { .. }
/// }
/// ```
declare_lint! {
pub WRONG_PUB_SELF_CONVENTION, Allow,
"defining a public method named with an established prefix (like \"into_\") that takes \
`self` with the wrong convention"
}
/// **What it does:** This lint checks for usage of `ok().expect(..)`.
///
/// **Why is this bad?** Because you usually call `expect()` on the `Result` directly to get a good error message.
///
/// **Known problems:** None.
///
/// **Example:** `x.ok().expect("why did I do this again?")`
declare_lint! {
pub OK_EXPECT, Warn,
"using `ok().expect()`, which gives worse error messages than \
calling `expect` directly on the Result"
}
/// **What it does:** This lint checks for usage of `_.map(_).unwrap_or(_)`.
///
/// **Why is this bad?** Readability, this can be written more concisely as `_.map_or(_, _)`.
///
/// **Known problems:** None.
///
/// **Example:** `x.map(|a| a + 1).unwrap_or(0)`
declare_lint! {
pub OPTION_MAP_UNWRAP_OR, Warn,
"using `Option.map(f).unwrap_or(a)`, which is more succinctly expressed as \
`map_or(a, f)`"
}
/// **What it does:** This lint `Warn`s on `_.map(_).unwrap_or_else(_)`.
///
/// **Why is this bad?** Readability, this can be written more concisely as `_.map_or_else(_, _)`.
///
/// **Known problems:** None.
///
/// **Example:** `x.map(|a| a + 1).unwrap_or_else(some_function)`
declare_lint! {
pub OPTION_MAP_UNWRAP_OR_ELSE, Warn,
"using `Option.map(f).unwrap_or_else(g)`, which is more succinctly expressed as \
`map_or_else(g, f)`"
}
/// **What it does:** This lint `Warn`s on `_.filter(_).next()`.
///
/// **Why is this bad?** Readability, this can be written more concisely as `_.find(_)`.
///
/// **Known problems:** None.
///
/// **Example:** `iter.filter(|x| x == 0).next()`
declare_lint! {
pub FILTER_NEXT, Warn,
"using `filter(p).next()`, which is more succinctly expressed as `.find(p)`"
}
/// **What it does:** This lint `Warn`s on an iterator search (such as `find()`, `position()`, or
/// `rposition()`) followed by a call to `is_some()`.
///
/// **Why is this bad?** Readability, this can be written more concisely as `_.any(_)`.
///
/// **Known problems:** None.
///
/// **Example:** `iter.find(|x| x == 0).is_some()`
declare_lint! {
pub SEARCH_IS_SOME, Warn,
"using an iterator search followed by `is_some()`, which is more succinctly \
expressed as a call to `any()`"
}
/// **What it does:** This lint `Warn`s on using `.chars().next()` on a `str` to check if it
/// starts with a given char.
///
/// **Why is this bad?** Readability, this can be written more concisely as `_.starts_with(_)`.
///
/// **Known problems:** None.
///
/// **Example:** `name.chars().next() == Some('_')`
declare_lint! {
pub CHARS_NEXT_CMP, Warn,
"using `.chars().next()` to check if a string starts with a char"
}
/// **What it does:** This lint checks for calls to `.or(foo(..))`, `.unwrap_or(foo(..))`, etc., and
/// suggests to use `or_else`, `unwrap_or_else`, etc., or `unwrap_or_default` instead.
///
/// **Why is this bad?** The function will always be called and potentially allocate an object
/// in expressions such as:
/// ```rust
/// foo.unwrap_or(String::new())
/// ```
/// this can instead be written:
/// ```rust
/// foo.unwrap_or_else(String::new)
/// ```
/// or
/// ```rust
/// foo.unwrap_or_default()
/// ```
///
/// **Known problems:** If the function as side-effects, not calling it will change the semantic of
/// the program, but you shouldn't rely on that anyway.
declare_lint! {
pub OR_FUN_CALL, Warn,
"using any `*or` method when the `*or_else` would do"
}
/// **What it does:** This lint checks for usage of `.extend(s)` on a `Vec` to extend the vector by a slice.
///
/// **Why is this bad?** Since Rust 1.6, the `extend_from_slice(_)` method is stable and at least for now faster.
///
/// **Known problems:** None.
///
/// **Example:** `my_vec.extend(&xs)`
declare_lint! {
pub EXTEND_FROM_SLICE, Warn,
"`.extend_from_slice(_)` is a faster way to extend a Vec by a slice"
}
/// **What it does:** This lint warns on using `.clone()` on a `Copy` type.
///
/// **Why is this bad?** The only reason `Copy` types implement `Clone` is for generics, not for
/// using the `clone` method on a concrete type.
///
/// **Known problems:** None.
///
/// **Example:** `42u64.clone()`
declare_lint! {
pub CLONE_ON_COPY, Warn, "using `clone` on a `Copy` type"
}
/// **What it does:** This lint warns on using `.clone()` on an `&&T`
///
/// **Why is this bad?** Cloning an `&&T` copies the inner `&T`, instead of cloning the underlying
/// `T`
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// fn main() {
/// let x = vec![1];
/// let y = &&x;
/// let z = y.clone();
/// println!("{:p} {:p}",*y, z); // prints out the same pointer
/// }
/// ```
declare_lint! {
pub CLONE_DOUBLE_REF, Warn, "using `clone` on `&&T`"
}
/// **What it does:** This lint warns about `new` not returning `Self`.
///
/// **Why is this bad?** As a convention, `new` methods are used to make a new instance of a type.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// impl Foo {
/// fn new(..) -> NotAFoo {
/// }
/// }
/// ```
declare_lint! {
pub NEW_RET_NO_SELF, Warn, "not returning `Self` in a `new` method"
}
/// **What it does:** This lint checks for string methods that receive a single-character `str` as an argument, e.g. `_.split("x")`.
///
/// **Why is this bad?** Performing these methods using a `char` is faster than using a `str`.
///
/// **Known problems:** Does not catch multi-byte unicode characters.
///
/// **Example:** `_.split("x")` could be `_.split('x')`
declare_lint! {
pub SINGLE_CHAR_PATTERN,
Warn,
"using a single-character str where a char could be used, e.g. \
`_.split(\"x\")`"
}
impl LintPass for MethodsPass {
fn get_lints(&self) -> LintArray {
lint_array!(EXTEND_FROM_SLICE,
OPTION_UNWRAP_USED,
RESULT_UNWRAP_USED,
STR_TO_STRING,
STRING_TO_STRING,
SHOULD_IMPLEMENT_TRAIT,
WRONG_SELF_CONVENTION,
WRONG_PUB_SELF_CONVENTION,
OK_EXPECT,
OPTION_MAP_UNWRAP_OR,
OPTION_MAP_UNWRAP_OR_ELSE,
OR_FUN_CALL,
CHARS_NEXT_CMP,
CLONE_ON_COPY,
CLONE_DOUBLE_REF,
NEW_RET_NO_SELF,
SINGLE_CHAR_PATTERN)
}
}
impl LateLintPass for MethodsPass {
fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
if in_macro(cx, expr.span) {
return;
}
match expr.node {
ExprMethodCall(name, _, ref args) => {
// Chain calls
if let Some(arglists) = method_chain_args(expr, &["unwrap"]) {
lint_unwrap(cx, expr, arglists[0]);
} else if let Some(arglists) = method_chain_args(expr, &["to_string"]) {
lint_to_string(cx, expr, arglists[0]);
} else if let Some(arglists) = method_chain_args(expr, &["ok", "expect"]) {
lint_ok_expect(cx, expr, arglists[0]);
} else if let Some(arglists) = method_chain_args(expr, &["map", "unwrap_or"]) {
lint_map_unwrap_or(cx, expr, arglists[0], arglists[1]);
} else if let Some(arglists) = method_chain_args(expr, &["map", "unwrap_or_else"]) {
lint_map_unwrap_or_else(cx, expr, arglists[0], arglists[1]);
} else if let Some(arglists) = method_chain_args(expr, &["filter", "next"]) {
lint_filter_next(cx, expr, arglists[0]);
} else if let Some(arglists) = method_chain_args(expr, &["find", "is_some"]) {
lint_search_is_some(cx, expr, "find", arglists[0], arglists[1]);
} else if let Some(arglists) = method_chain_args(expr, &["position", "is_some"]) {
lint_search_is_some(cx, expr, "position", arglists[0], arglists[1]);
} else if let Some(arglists) = method_chain_args(expr, &["rposition", "is_some"]) {
lint_search_is_some(cx, expr, "rposition", arglists[0], arglists[1]);
} else if let Some(arglists) = method_chain_args(expr, &["extend"]) {
lint_extend(cx, expr, arglists[0]);
}
lint_or_fun_call(cx, expr, &name.node.as_str(), &args);
if args.len() == 1 && name.node.as_str() == "clone" {
lint_clone_on_copy(cx, expr);
lint_clone_double_ref(cx, expr, &args[0]);
}
for &(method, pos) in &PATTERN_METHODS {
if name.node.as_str() == method && args.len() > pos {
lint_single_char_pattern(cx, expr, &args[pos]);
}
}
}
ExprBinary(op, ref lhs, ref rhs) if op.node == BiEq || op.node == BiNe => {
if !lint_chars_next(cx, expr, lhs, rhs, op.node == BiEq) {
lint_chars_next(cx, expr, rhs, lhs, op.node == BiEq);
}
}
_ => (),
}
}
fn check_item(&mut self, cx: &LateContext, item: &Item) {
if in_external_macro(cx, item.span) {
return;
}
if let ItemImpl(_, _, _, None, _, ref items) = item.node {
for implitem in items {
let name = implitem.name;
if let ImplItemKind::Method(ref sig, _) = implitem.node {
// check missing trait implementations
for &(method_name, n_args, self_kind, out_type, trait_name) in &TRAIT_METHODS {
if_let_chain! {
[
name.as_str() == method_name,
sig.decl.inputs.len() == n_args,
out_type.matches(&sig.decl.output),
self_kind.matches(&sig.explicit_self.node, false)
], {
span_lint(cx, SHOULD_IMPLEMENT_TRAIT, implitem.span, &format!(
"defining a method called `{}` on this type; consider implementing \
the `{}` trait or choosing a less ambiguous name", name, trait_name));
}
}
}
// check conventions w.r.t. conversion method names and predicates
let ty = cx.tcx.lookup_item_type(cx.tcx.map.local_def_id(item.id)).ty;
let is_copy = is_copy(cx, &ty, &item);
for &(ref conv, self_kinds) in &CONVENTIONS {
if conv.check(&name.as_str()) &&
!self_kinds.iter().any(|k| k.matches(&sig.explicit_self.node, is_copy)) {
let lint = if item.vis == Visibility::Public {
WRONG_PUB_SELF_CONVENTION
} else {
WRONG_SELF_CONVENTION
};
span_lint(cx,
lint,
sig.explicit_self.span,
&format!("methods called `{}` usually take {}; consider choosing a less \
ambiguous name",
conv,
&self_kinds.iter()
.map(|k| k.description())
.collect::<Vec<_>>()
.join(" or ")));
}
}
let ret_ty = return_ty(cx.tcx.node_id_to_type(implitem.id));
if &name.as_str() == &"new" && !ret_ty.map_or(false, |ret_ty| ret_ty.walk().any(|t| t == ty)) {
span_lint(cx,
NEW_RET_NO_SELF,
sig.explicit_self.span,
"methods called `new` usually return `Self`");
}
}
}
}
}
}
/// Checks for the `OR_FUN_CALL` lint.
fn lint_or_fun_call(cx: &LateContext, expr: &Expr, name: &str, args: &[P<Expr>]) {
/// Check for `unwrap_or(T::new())` or `unwrap_or(T::default())`.
fn check_unwrap_or_default(cx: &LateContext, name: &str, fun: &Expr, self_expr: &Expr, arg: &Expr,
or_has_args: bool, span: Span)
-> bool {
if or_has_args {
return false;
}
if name == "unwrap_or" {
if let ExprPath(_, ref path) = fun.node {
let path: &str = &path.segments
.last()
.expect("A path must have at least one segment")
.identifier
.name
.as_str();
if ["default", "new"].contains(&path) {
let arg_ty = cx.tcx.expr_ty(arg);
let default_trait_id = if let Some(default_trait_id) = get_trait_def_id(cx, &DEFAULT_TRAIT_PATH) {
default_trait_id
} else {
return false;
};
if implements_trait(cx, arg_ty, default_trait_id, Vec::new()) {
span_lint(cx,
OR_FUN_CALL,
span,
&format!("use of `{}` followed by a call to `{}`", name, path))
.span_suggestion(span,
"try this",
format!("{}.unwrap_or_default()", snippet(cx, self_expr.span, "_")));
return true;
}
}
}
}
false
}
/// Check for `*or(foo())`.
fn check_general_case(cx: &LateContext, name: &str, fun: &Expr, self_expr: &Expr, arg: &Expr, or_has_args: bool,
span: Span) {
// (path, fn_has_argument, methods)
let know_types: &[(&[_], _, &[_], _)] = &[(&BTREEMAP_ENTRY_PATH, false, &["or_insert"], "with"),
(&HASHMAP_ENTRY_PATH, false, &["or_insert"], "with"),
(&OPTION_PATH,
false,
&["map_or", "ok_or", "or", "unwrap_or"],
"else"),
(&RESULT_PATH, true, &["or", "unwrap_or"], "else")];
let self_ty = cx.tcx.expr_ty(self_expr);
let (fn_has_arguments, poss, suffix) = if let Some(&(_, fn_has_arguments, poss, suffix)) =
know_types.iter().find(|&&i| match_type(cx, self_ty, i.0)) {
(fn_has_arguments, poss, suffix)
} else {
return;
};
if !poss.contains(&name) {
return;
}
let sugg: Cow<_> = match (fn_has_arguments, !or_has_args) {
(true, _) => format!("|_| {}", snippet(cx, arg.span, "..")).into(),
(false, false) => format!("|| {}", snippet(cx, arg.span, "..")).into(),
(false, true) => snippet(cx, fun.span, ".."),
};
span_lint(cx, OR_FUN_CALL, span, &format!("use of `{}` followed by a function call", name))
.span_suggestion(span,
"try this",
format!("{}.{}_{}({})", snippet(cx, self_expr.span, "_"), name, suffix, sugg));
}
if args.len() == 2 {
if let ExprCall(ref fun, ref or_args) = args[1].node {
let or_has_args = !or_args.is_empty();
if !check_unwrap_or_default(cx, name, fun, &args[0], &args[1], or_has_args, expr.span) {
check_general_case(cx, name, fun, &args[0], &args[1], or_has_args, expr.span);
}
}
}
}
/// Checks for the `CLONE_ON_COPY` lint.
fn lint_clone_on_copy(cx: &LateContext, expr: &Expr) {
let ty = cx.tcx.expr_ty(expr);
let parent = cx.tcx.map.get_parent(expr.id);
let parameter_environment = ty::ParameterEnvironment::for_item(cx.tcx, parent);
if !ty.moves_by_default(&parameter_environment, expr.span) {
span_lint(cx, CLONE_ON_COPY, expr.span, "using `clone` on a `Copy` type");
}
}
/// Checks for the `CLONE_DOUBLE_REF` lint.
fn lint_clone_double_ref(cx: &LateContext, expr: &Expr, arg: &Expr) {
let ty = cx.tcx.expr_ty(arg);
if let ty::TyRef(_, ty::TypeAndMut { ty: ref inner, .. }) = ty.sty {
if let ty::TyRef(..) = inner.sty {
let mut db = span_lint(cx,
CLONE_DOUBLE_REF,
expr.span,
"using `clone` on a double-reference; \
this will copy the reference instead of cloning \
the inner type");
if let Some(snip) = snippet_opt(cx, arg.span) {
db.span_suggestion(expr.span, "try dereferencing it", format!("(*{}).clone()", snip));
}
}
}
}
fn lint_extend(cx: &LateContext, expr: &Expr, args: &MethodArgs) {
let (obj_ty, _) = walk_ptrs_ty_depth(cx.tcx.expr_ty(&args[0]));
if !match_type(cx, obj_ty, &VEC_PATH) {
return;
}
let arg_ty = cx.tcx.expr_ty(&args[1]);
if let Some((span, r)) = derefs_to_slice(cx, &args[1], &arg_ty) {
span_lint(cx, EXTEND_FROM_SLICE, expr.span, "use of `extend` to extend a Vec by a slice")
.span_suggestion(expr.span,
"try this",
format!("{}.extend_from_slice({}{})",
snippet(cx, args[0].span, "_"),
r,
snippet(cx, span, "_")));
}
}
fn derefs_to_slice(cx: &LateContext, expr: &Expr, ty: &ty::Ty) -> Option<(Span, &'static str)> {
fn may_slice(cx: &LateContext, ty: &ty::Ty) -> bool {
match ty.sty {
ty::TySlice(_) => true,
ty::TyStruct(..) => match_type(cx, ty, &VEC_PATH),
ty::TyArray(_, size) => size < 32,
ty::TyRef(_, ty::TypeAndMut { ty: ref inner, .. }) |
ty::TyBox(ref inner) => may_slice(cx, inner),
_ => false,
}
}
if let ExprMethodCall(name, _, ref args) = expr.node {
if &name.node.as_str() == &"iter" && may_slice(cx, &cx.tcx.expr_ty(&args[0])) {
Some((args[0].span, "&"))
} else {
None
}
} else {
match ty.sty {
ty::TySlice(_) => Some((expr.span, "")),
ty::TyRef(_, ty::TypeAndMut { ty: ref inner, .. }) |
ty::TyBox(ref inner) => {
if may_slice(cx, inner) {
Some((expr.span, ""))
} else {
None
}
}
_ => None,
}
}
}
#[allow(ptr_arg)]
// Type of MethodArgs is potentially a Vec
/// lint use of `unwrap()` for `Option`s and `Result`s
fn lint_unwrap(cx: &LateContext, expr: &Expr, unwrap_args: &MethodArgs) {
let (obj_ty, _) = walk_ptrs_ty_depth(cx.tcx.expr_ty(&unwrap_args[0]));
let mess = if match_type(cx, obj_ty, &OPTION_PATH) {
Some((OPTION_UNWRAP_USED, "an Option", "None"))
} else if match_type(cx, obj_ty, &RESULT_PATH) {
Some((RESULT_UNWRAP_USED, "a Result", "Err"))
} else {
None
};
if let Some((lint, kind, none_value)) = mess {
span_lint(cx,
lint,
expr.span,
&format!("used unwrap() on {} value. If you don't want to handle the {} case gracefully, consider \
using expect() to provide a better panic
message",
kind,
none_value));
}
}
#[allow(ptr_arg)]
// Type of MethodArgs is potentially a Vec
/// lint use of `to_string()` for `&str`s and `String`s
fn lint_to_string(cx: &LateContext, expr: &Expr, to_string_args: &MethodArgs) {
let (obj_ty, ptr_depth) = walk_ptrs_ty_depth(cx.tcx.expr_ty(&to_string_args[0]));
if obj_ty.sty == ty::TyStr {
let mut arg_str = snippet(cx, to_string_args[0].span, "_");
if ptr_depth > 1 {
arg_str = Cow::Owned(format!("({}{})", iter::repeat('*').take(ptr_depth - 1).collect::<String>(), arg_str));
}
span_lint(cx, STR_TO_STRING, expr.span, &format!("`{}.to_owned()` is faster", arg_str));
} else if match_type(cx, obj_ty, &STRING_PATH) {
span_lint(cx,
STRING_TO_STRING,
expr.span,
"`String::to_string` is an inefficient way to clone a `String`; use `clone()` instead");
}
}
#[allow(ptr_arg)]
// Type of MethodArgs is potentially a Vec
/// lint use of `ok().expect()` for `Result`s
fn lint_ok_expect(cx: &LateContext, expr: &Expr, ok_args: &MethodArgs) {
// lint if the caller of `ok()` is a `Result`
if match_type(cx, cx.tcx.expr_ty(&ok_args[0]), &RESULT_PATH) {
let result_type = cx.tcx.expr_ty(&ok_args[0]);
if let Some(error_type) = get_error_type(cx, result_type) {
if has_debug_impl(error_type, cx) {
span_lint(cx,
OK_EXPECT,
expr.span,
"called `ok().expect()` on a Result value. You can call `expect` directly on the `Result`");
}
}
}
}
#[allow(ptr_arg)]
// Type of MethodArgs is potentially a Vec
/// lint use of `map().unwrap_or()` for `Option`s
fn lint_map_unwrap_or(cx: &LateContext, expr: &Expr, map_args: &MethodArgs, unwrap_args: &MethodArgs) {
// lint if the caller of `map()` is an `Option`
if match_type(cx, cx.tcx.expr_ty(&map_args[0]), &OPTION_PATH) {
// lint message
let msg = "called `map(f).unwrap_or(a)` on an Option value. This can be done more directly by calling \
`map_or(a, f)` instead";
// get snippets for args to map() and unwrap_or()
let map_snippet = snippet(cx, map_args[1].span, "..");
let unwrap_snippet = snippet(cx, unwrap_args[1].span, "..");
// lint, with note if neither arg is > 1 line and both map() and
// unwrap_or() have the same span
let multiline = map_snippet.lines().count() > 1 || unwrap_snippet.lines().count() > 1;
let same_span = map_args[1].span.expn_id == unwrap_args[1].span.expn_id;
if same_span && !multiline {
span_note_and_lint(cx,
OPTION_MAP_UNWRAP_OR,
expr.span,
msg,
expr.span,
&format!("replace `map({0}).unwrap_or({1})` with `map_or({1}, {0})`",
map_snippet,
unwrap_snippet));
} else if same_span && multiline {
span_lint(cx, OPTION_MAP_UNWRAP_OR, expr.span, msg);
};
}
}
#[allow(ptr_arg)]
// Type of MethodArgs is potentially a Vec
/// lint use of `map().unwrap_or_else()` for `Option`s
fn lint_map_unwrap_or_else(cx: &LateContext, expr: &Expr, map_args: &MethodArgs, unwrap_args: &MethodArgs) {
// lint if the caller of `map()` is an `Option`
if match_type(cx, cx.tcx.expr_ty(&map_args[0]), &OPTION_PATH) {
// lint message
let msg = "called `map(f).unwrap_or_else(g)` on an Option value. This can be done more directly by calling \
`map_or_else(g, f)` instead";
// get snippets for args to map() and unwrap_or_else()
let map_snippet = snippet(cx, map_args[1].span, "..");
let unwrap_snippet = snippet(cx, unwrap_args[1].span, "..");
// lint, with note if neither arg is > 1 line and both map() and
// unwrap_or_else() have the same span
let multiline = map_snippet.lines().count() > 1 || unwrap_snippet.lines().count() > 1;
let same_span = map_args[1].span.expn_id == unwrap_args[1].span.expn_id;
if same_span && !multiline {
span_note_and_lint(cx,
OPTION_MAP_UNWRAP_OR_ELSE,
expr.span,
msg,
expr.span,
&format!("replace `map({0}).unwrap_or_else({1})` with `with map_or_else({1}, {0})`",
map_snippet,
unwrap_snippet));
} else if same_span && multiline {
span_lint(cx, OPTION_MAP_UNWRAP_OR_ELSE, expr.span, msg);
};
}
}
#[allow(ptr_arg)]
// Type of MethodArgs is potentially a Vec
/// lint use of `filter().next() for Iterators`
fn lint_filter_next(cx: &LateContext, expr: &Expr, filter_args: &MethodArgs) {
// lint if caller of `.filter().next()` is an Iterator
if match_trait_method(cx, expr, &["core", "iter", "Iterator"]) {
let msg = "called `filter(p).next()` on an Iterator. This is more succinctly expressed by calling `.find(p)` \
instead.";
let filter_snippet = snippet(cx, filter_args[1].span, "..");
if filter_snippet.lines().count() <= 1 {
// add note if not multi-line
span_note_and_lint(cx,
FILTER_NEXT,
expr.span,
msg,
expr.span,
&format!("replace `filter({0}).next()` with `find({0})`", filter_snippet));
} else {
span_lint(cx, FILTER_NEXT, expr.span, msg);
}
}
}
#[allow(ptr_arg)]
// Type of MethodArgs is potentially a Vec
/// lint searching an Iterator followed by `is_some()`
fn lint_search_is_some(cx: &LateContext, expr: &Expr, search_method: &str, search_args: &MethodArgs,
is_some_args: &MethodArgs) {
// lint if caller of search is an Iterator
if match_trait_method(cx, &*is_some_args[0], &["core", "iter", "Iterator"]) {
let msg = format!("called `is_some()` after searching an iterator with {}. This is more succinctly expressed \
by calling `any()`.",
search_method);
let search_snippet = snippet(cx, search_args[1].span, "..");
if search_snippet.lines().count() <= 1 {
// add note if not multi-line
span_note_and_lint(cx,
SEARCH_IS_SOME,
expr.span,
&msg,
expr.span,
&format!("replace `{0}({1}).is_some()` with `any({1})`", search_method, search_snippet));
} else {
span_lint(cx, SEARCH_IS_SOME, expr.span, &msg);
}
}
}
/// Checks for the `CHARS_NEXT_CMP` lint.
fn lint_chars_next(cx: &LateContext, expr: &Expr, chain: &Expr, other: &Expr, eq: bool) -> bool {
if_let_chain! {[
let Some(args) = method_chain_args(chain, &["chars", "next"]),
let ExprCall(ref fun, ref arg_char) = other.node,
arg_char.len() == 1,
let ExprPath(None, ref path) = fun.node,
path.segments.len() == 1 && path.segments[0].identifier.name.as_str() == "Some"
], {
let self_ty = walk_ptrs_ty(cx.tcx.expr_ty_adjusted(&args[0][0]));
if self_ty.sty != ty::TyStr {
return false;
}
span_lint_and_then(cx,
CHARS_NEXT_CMP,
expr.span,
"you should use the `starts_with` method",
|db| {
let sugg = format!("{}{}.starts_with({})",
if eq { "" } else { "!" },
snippet(cx, args[0][0].span, "_"),
snippet(cx, arg_char[0].span, "_")
);
db.span_suggestion(expr.span, "like this", sugg);
});
return true;
}}
false
}
/// lint for length-1 `str`s for methods in `PATTERN_METHODS`
fn lint_single_char_pattern(cx: &LateContext, expr: &Expr, arg: &Expr) {
if let Ok(ConstVal::Str(r)) = eval_const_expr_partial(cx.tcx, arg, ExprTypeChecked, None) {
if r.len() == 1 {
let hint = snippet(cx, expr.span, "..").replace(&format!("\"{}\"", r), &format!("'{}'", r));
span_lint_and_then(cx,
SINGLE_CHAR_PATTERN,
arg.span,
"single-character string constant used as pattern",
|db| {
db.span_suggestion(expr.span, "try using a char instead:", hint);
});
}
}
}
/// Given a `Result<T, E>` type, return its error type (`E`).
fn get_error_type<'a>(cx: &LateContext, ty: ty::Ty<'a>) -> Option<ty::Ty<'a>> {
if !match_type(cx, ty, &RESULT_PATH) {
return None;
}
if let ty::TyEnum(_, substs) = ty.sty {
if let Some(err_ty) = substs.types.opt_get(TypeSpace, 1) {
return Some(err_ty);
}
}
None
}
/// This checks whether a given type is known to implement Debug.
fn has_debug_impl<'a, 'b>(ty: ty::Ty<'a>, cx: &LateContext<'b, 'a>) -> bool {
match cx.tcx.lang_items.debug_trait() {
Some(debug) => implements_trait(cx, ty, debug, Vec::new()),
None => false,
}
}
enum Convention {
Eq(&'static str),
StartsWith(&'static str),
}
#[cfg_attr(rustfmt, rustfmt_skip)]
const CONVENTIONS: [(Convention, &'static [SelfKind]); 6] = [
(Convention::Eq("new"), &[SelfKind::No]),
(Convention::StartsWith("as_"), &[SelfKind::Ref, SelfKind::RefMut]),
(Convention::StartsWith("from_"), &[SelfKind::No]),
(Convention::StartsWith("into_"), &[SelfKind::Value]),
(Convention::StartsWith("is_"), &[SelfKind::Ref, SelfKind::No]),
(Convention::StartsWith("to_"), &[SelfKind::Ref]),
];
#[cfg_attr(rustfmt, rustfmt_skip)]
const TRAIT_METHODS: [(&'static str, usize, SelfKind, OutType, &'static str); 30] = [
("add", 2, SelfKind::Value, OutType::Any, "std::ops::Add"),
("as_mut", 1, SelfKind::RefMut, OutType::Ref, "std::convert::AsMut"),
("as_ref", 1, SelfKind::Ref, OutType::Ref, "std::convert::AsRef"),
("bitand", 2, SelfKind::Value, OutType::Any, "std::ops::BitAnd"),
("bitor", 2, SelfKind::Value, OutType::Any, "std::ops::BitOr"),
("bitxor", 2, SelfKind::Value, OutType::Any, "std::ops::BitXor"),
("borrow", 1, SelfKind::Ref, OutType::Ref, "std::borrow::Borrow"),
("borrow_mut", 1, SelfKind::RefMut, OutType::Ref, "std::borrow::BorrowMut"),
("clone", 1, SelfKind::Ref, OutType::Any, "std::clone::Clone"),
("cmp", 2, SelfKind::Ref, OutType::Any, "std::cmp::Ord"),
("default", 0, SelfKind::No, OutType::Any, "std::default::Default"),
("deref", 1, SelfKind::Ref, OutType::Ref, "std::ops::Deref"),
("deref_mut", 1, SelfKind::RefMut, OutType::Ref, "std::ops::DerefMut"),
("div", 2, SelfKind::Value, OutType::Any, "std::ops::Div"),
("drop", 1, SelfKind::RefMut, OutType::Unit, "std::ops::Drop"),
("eq", 2, SelfKind::Ref, OutType::Bool, "std::cmp::PartialEq"),
("from_iter", 1, SelfKind::No, OutType::Any, "std::iter::FromIterator"),
("from_str", 1, SelfKind::No, OutType::Any, "std::str::FromStr"),
("hash", 2, SelfKind::Ref, OutType::Unit, "std::hash::Hash"),
("index", 2, SelfKind::Ref, OutType::Ref, "std::ops::Index"),
("index_mut", 2, SelfKind::RefMut, OutType::Ref, "std::ops::IndexMut"),
("into_iter", 1, SelfKind::Value, OutType::Any, "std::iter::IntoIterator"),
("mul", 2, SelfKind::Value, OutType::Any, "std::ops::Mul"),
("neg", 1, SelfKind::Value, OutType::Any, "std::ops::Neg"),
("next", 1, SelfKind::RefMut, OutType::Any, "std::iter::Iterator"),
("not", 1, SelfKind::Value, OutType::Any, "std::ops::Not"),
("rem", 2, SelfKind::Value, OutType::Any, "std::ops::Rem"),
("shl", 2, SelfKind::Value, OutType::Any, "std::ops::Shl"),
("shr", 2, SelfKind::Value, OutType::Any, "std::ops::Shr"),
("sub", 2, SelfKind::Value, OutType::Any, "std::ops::Sub"),
];
#[cfg_attr(rustfmt, rustfmt_skip)]
const PATTERN_METHODS: [(&'static str, usize); 17] = [
("contains", 1),
("starts_with", 1),
("ends_with", 1),
("find", 1),
("rfind", 1),
("split", 1),
("rsplit", 1),
("split_terminator", 1),
("rsplit_terminator", 1),
("splitn", 2),
("rsplitn", 2),
("matches", 1),
("rmatches", 1),
("match_indices", 1),
("rmatch_indices", 1),
("trim_left_matches", 1),
("trim_right_matches", 1),
];
#[derive(Clone, Copy)]
enum SelfKind {
Value,
Ref,
RefMut,
No,
}
impl SelfKind {
fn matches(&self, slf: &ExplicitSelf_, allow_value_for_ref: bool) -> bool {
match (self, slf) {
(&SelfKind::Value, &SelfValue(_)) |
(&SelfKind::Ref, &SelfRegion(_, Mutability::MutImmutable, _)) |
(&SelfKind::RefMut, &SelfRegion(_, Mutability::MutMutable, _)) |
(&SelfKind::No, &SelfStatic) => true,
(&SelfKind::Ref, &SelfValue(_)) | (&SelfKind::RefMut, &SelfValue(_)) => allow_value_for_ref,
(_, &SelfExplicit(ref ty, _)) => self.matches_explicit_type(ty, allow_value_for_ref),
_ => false,
}
}
fn matches_explicit_type(&self, ty: &Ty, allow_value_for_ref: bool) -> bool {
match (self, &ty.node) {
(&SelfKind::Value, &TyPath(..)) |
(&SelfKind::Ref, &TyRptr(_, MutTy { mutbl: Mutability::MutImmutable, .. })) |
(&SelfKind::RefMut, &TyRptr(_, MutTy { mutbl: Mutability::MutMutable, .. })) => true,
(&SelfKind::Ref, &TyPath(..)) |
(&SelfKind::RefMut, &TyPath(..)) => allow_value_for_ref,
_ => false,
}
}
fn description(&self) -> &'static str {
match *self {
SelfKind::Value => "self by value",
SelfKind::Ref => "self by reference",
SelfKind::RefMut => "self by mutable reference",
SelfKind::No => "no self",
}
}
}
impl Convention {
fn check(&self, other: &str) -> bool {
match *self {
Convention::Eq(this) => this == other,
Convention::StartsWith(this) => other.starts_with(this),
}
}
}
impl fmt::Display for Convention {
fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
match *self {
Convention::Eq(this) => this.fmt(f),
Convention::StartsWith(this) => this.fmt(f).and_then(|_| '*'.fmt(f)),
}
}
}
#[derive(Clone, Copy)]
enum OutType {
Unit,
Bool,
Any,
Ref,
}
impl OutType {
fn matches(&self, ty: &FunctionRetTy) -> bool {
match (self, ty) {
(&OutType::Unit, &DefaultReturn(_)) => true,
(&OutType::Unit, &Return(ref ty)) if ty.node == TyTup(vec![].into()) => true,
(&OutType::Bool, &Return(ref ty)) if is_bool(ty) => true,
(&OutType::Any, &Return(ref ty)) if ty.node != TyTup(vec![].into()) => true,
(&OutType::Ref, &Return(ref ty)) => {
if let TyRptr(_, _) = ty.node {
true
} else {
false
}
}
_ => false,
}
}
}
fn is_bool(ty: &Ty) -> bool {
if let TyPath(None, ref p) = ty.node {
if match_path(p, &["bool"]) {
return true;
}
}
false
}
fn is_copy<'a, 'ctx>(cx: &LateContext<'a, 'ctx>, ty: ty::Ty<'ctx>, item: &Item) -> bool {
let env = ty::ParameterEnvironment::for_item(cx.tcx, item.id);
!ty.subst(cx.tcx, &env.free_substs).moves_by_default(&env, item.span)
}
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