1 use clippy_utils
::diagnostics
::{span_lint, span_lint_and_help, span_lint_and_sugg}
;
2 use clippy_utils
::source
::{snippet, snippet_with_applicability}
;
3 use clippy_utils
::ty
::is_type_diagnostic_item
;
4 use clippy_utils
::{get_parent_expr, is_lint_allowed, match_function_call, method_calls, paths}
;
5 use clippy_utils
::{peel_blocks, SpanlessEq}
;
6 use if_chain
::if_chain
;
7 use rustc_errors
::Applicability
;
8 use rustc_hir
::def_id
::DefId
;
9 use rustc_hir
::{BinOpKind, BorrowKind, Expr, ExprKind, LangItem, QPath}
;
10 use rustc_lint
::{LateContext, LateLintPass, LintContext}
;
11 use rustc_middle
::lint
::in_external_macro
;
13 use rustc_session
::{declare_lint_pass, declare_tool_lint}
;
14 use rustc_span
::source_map
::Spanned
;
17 declare_clippy_lint
! {
19 /// Checks for string appends of the form `x = x + y` (without
22 /// ### Why is this bad?
23 /// It's not really bad, but some people think that the
24 /// `.push_str(_)` method is more readable.
28 /// let mut x = "Hello".to_owned();
29 /// x = x + ", World";
33 /// x.push_str(", World");
35 #[clippy::version = "pre 1.29.0"]
36 pub STRING_ADD_ASSIGN
,
38 "using `x = x + ..` where x is a `String` instead of `push_str()`"
41 declare_clippy_lint
! {
43 /// Checks for all instances of `x + _` where `x` is of type
44 /// `String`, but only if [`string_add_assign`](#string_add_assign) does *not*
47 /// ### Why is this bad?
48 /// It's not bad in and of itself. However, this particular
49 /// `Add` implementation is asymmetric (the other operand need not be `String`,
50 /// but `x` does), while addition as mathematically defined is symmetric, also
51 /// the `String::push_str(_)` function is a perfectly good replacement.
52 /// Therefore, some dislike it and wish not to have it in their code.
54 /// That said, other people think that string addition, having a long tradition
55 /// in other languages is actually fine, which is why we decided to make this
56 /// particular lint `allow` by default.
60 /// let x = "Hello".to_owned();
66 /// let mut x = "Hello".to_owned();
67 /// x.push_str(", World");
69 #[clippy::version = "pre 1.29.0"]
72 "using `x + ..` where x is a `String` instead of `push_str()`"
75 declare_clippy_lint
! {
77 /// Checks for the `as_bytes` method called on string literals
78 /// that contain only ASCII characters.
80 /// ### Why is this bad?
81 /// Byte string literals (e.g., `b"foo"`) can be used
82 /// instead. They are shorter but less discoverable than `as_bytes()`.
84 /// ### Known problems
85 /// `"str".as_bytes()` and the suggested replacement of `b"str"` are not
86 /// equivalent because they have different types. The former is `&[u8]`
87 /// while the latter is `&[u8; 3]`. That means in general they will have a
88 /// different set of methods and different trait implementations.
91 /// fn f(v: Vec<u8>) {}
93 /// f("...".as_bytes().to_owned()); // works
94 /// f(b"...".to_owned()); // does not work, because arg is [u8; 3] not Vec<u8>
96 /// fn g(r: impl std::io::Read) {}
98 /// g("...".as_bytes()); // works
99 /// g(b"..."); // does not work
102 /// The actual equivalent of `"str".as_bytes()` with the same type is not
103 /// `b"str"` but `&b"str"[..]`, which is a great deal of punctuation and not
104 /// more readable than a function call.
108 /// let bstr = "a byte string".as_bytes();
113 /// let bstr = b"a byte string";
115 #[clippy::version = "pre 1.29.0"]
116 pub STRING_LIT_AS_BYTES
,
118 "calling `as_bytes` on a string literal instead of using a byte string literal"
121 declare_clippy_lint
! {
123 /// Checks for slice operations on strings
125 /// ### Why is this bad?
126 /// UTF-8 characters span multiple bytes, and it is easy to inadvertently confuse character
127 /// counts and string indices. This may lead to panics, and should warrant some test cases
128 /// containing wide UTF-8 characters. This lint is most useful in code that should avoid
129 /// panics at all costs.
131 /// ### Known problems
132 /// Probably lots of false positives. If an index comes from a known valid position (e.g.
133 /// obtained via `char_indices` over the same string), it is totally OK.
136 /// ```rust,should_panic
137 /// &"Ölkanne"[1..];
139 #[clippy::version = "1.58.0"]
145 declare_lint_pass
!(StringAdd
=> [STRING_ADD
, STRING_ADD_ASSIGN
, STRING_SLICE
]);
147 impl<'tcx
> LateLintPass
<'tcx
> for StringAdd
{
148 fn check_expr(&mut self, cx
: &LateContext
<'tcx
>, e
: &'tcx Expr
<'_
>) {
149 if in_external_macro(cx
.sess(), e
.span
) {
155 node
: BinOpKind
::Add
, ..
160 if is_string(cx
, left
) {
161 if !is_lint_allowed(cx
, STRING_ADD_ASSIGN
, e
.hir_id
) {
162 let parent
= get_parent_expr(cx
, e
);
163 if let Some(p
) = parent
{
164 if let ExprKind
::Assign(target
, _
, _
) = p
.kind
{
165 // avoid duplicate matches
166 if SpanlessEq
::new(cx
).eq_expr(target
, left
) {
176 "you added something to a string. Consider using `String::push_str()` instead",
180 ExprKind
::Assign(target
, src
, _
) => {
181 if is_string(cx
, target
) && is_add(cx
, src
, target
) {
186 "you assigned the result of adding something to this string. Consider using \
187 `String::push_str()` instead",
191 ExprKind
::Index(target
, _idx
) => {
192 let e_ty
= cx
.typeck_results().expr_ty(target
).peel_refs();
193 if matches
!(e_ty
.kind(), ty
::Str
) || is_type_diagnostic_item(cx
, e_ty
, sym
::String
) {
198 "indexing into a string may panic if the index is within a UTF-8 character",
207 fn is_string(cx
: &LateContext
<'_
>, e
: &Expr
<'_
>) -> bool
{
208 is_type_diagnostic_item(cx
, cx
.typeck_results().expr_ty(e
).peel_refs(), sym
::String
)
211 fn is_add(cx
: &LateContext
<'_
>, src
: &Expr
<'_
>, target
: &Expr
<'_
>) -> bool
{
212 match peel_blocks(src
).kind
{
215 node
: BinOpKind
::Add
, ..
219 ) => SpanlessEq
::new(cx
).eq_expr(target
, left
),
224 declare_clippy_lint
! {
226 /// Check if the string is transformed to byte array and casted back to string.
228 /// ### Why is this bad?
229 /// It's unnecessary, the string can be used directly.
233 /// std::str::from_utf8(&"Hello World!".as_bytes()[6..11]).unwrap();
238 /// &"Hello World!"[6..11];
240 #[clippy::version = "1.50.0"]
241 pub STRING_FROM_UTF8_AS_BYTES
,
243 "casting string slices to byte slices and back"
246 // Max length a b"foo" string can take
247 const MAX_LENGTH_BYTE_STRING_LIT
: usize = 32;
249 declare_lint_pass
!(StringLitAsBytes
=> [STRING_LIT_AS_BYTES
, STRING_FROM_UTF8_AS_BYTES
]);
251 impl<'tcx
> LateLintPass
<'tcx
> for StringLitAsBytes
{
252 fn check_expr(&mut self, cx
: &LateContext
<'tcx
>, e
: &'tcx Expr
<'_
>) {
253 use rustc_ast
::LitKind
;
256 // Find std::str::converts::from_utf8
257 if let Some(args
) = match_function_call(cx
, e
, &paths
::STR_FROM_UTF8
);
259 // Find string::as_bytes
260 if let ExprKind
::AddrOf(BorrowKind
::Ref
, _
, args
) = args
[0].kind
;
261 if let ExprKind
::Index(left
, right
) = args
.kind
;
262 let (method_names
, expressions
, _
) = method_calls(left
, 1);
263 if method_names
.len() == 1;
264 if expressions
.len() == 1;
265 if expressions
[0].len() == 1;
266 if method_names
[0] == sym
!(as_bytes
);
269 if let ExprKind
::Struct(QPath
::LangItem(LangItem
::Range
, ..), _
, _
) = right
.kind
;
272 let mut applicability
= Applicability
::MachineApplicable
;
273 let string_expression
= &expressions
[0][0];
275 let snippet_app
= snippet_with_applicability(
277 string_expression
.span
, "..",
283 STRING_FROM_UTF8_AS_BYTES
,
285 "calling a slice of `as_bytes()` with `from_utf8` should be not necessary",
287 format
!("Some(&{}[{}])", snippet_app
, snippet(cx
, right
.span
, "..")),
294 if let ExprKind
::MethodCall(path
, args
, _
) = &e
.kind
;
295 if path
.ident
.name
== sym
!(as_bytes
);
296 if let ExprKind
::Lit(lit
) = &args
[0].kind
;
297 if let LitKind
::Str(lit_content
, _
) = &lit
.node
;
299 let callsite
= snippet(cx
, args
[0].span
.source_callsite(), r
#""foo""#);
300 let mut applicability
= Applicability
::MachineApplicable
;
301 if callsite
.starts_with("include_str!") {
306 "calling `as_bytes()` on `include_str!(..)`",
307 "consider using `include_bytes!(..)` instead",
308 snippet_with_applicability(cx
, args
[0].span
, r
#""foo""#, &mut applicability).replacen(
315 } else if lit_content
.as_str().is_ascii()
316 && lit_content
.as_str().len() <= MAX_LENGTH_BYTE_STRING_LIT
317 && !args
[0].span
.from_expansion()
323 "calling `as_bytes()` on a string literal",
324 "consider using a byte string literal instead",
327 snippet_with_applicability(cx
, args
[0].span
, r
#""foo""#, &mut applicability)
336 if let ExprKind
::MethodCall(path
, [recv
], _
) = &e
.kind
;
337 if path
.ident
.name
== sym
!(into_bytes
);
338 if let ExprKind
::MethodCall(path
, [recv
], _
) = &recv
.kind
;
339 if matches
!(path
.ident
.name
.as_str(), "to_owned" | "to_string");
340 if let ExprKind
::Lit(lit
) = &recv
.kind
;
341 if let LitKind
::Str(lit_content
, _
) = &lit
.node
;
343 if lit_content
.as_str().is_ascii();
344 if lit_content
.as_str().len() <= MAX_LENGTH_BYTE_STRING_LIT
;
345 if !recv
.span
.from_expansion();
347 let mut applicability
= Applicability
::MachineApplicable
;
353 "calling `into_bytes()` on a string literal",
354 "consider using a byte string literal instead",
357 snippet_with_applicability(cx
, recv
.span
, r
#""..""#, &mut applicability)
366 declare_clippy_lint
! {
368 /// This lint checks for `.to_string()` method calls on values of type `&str`.
370 /// ### Why is this bad?
371 /// The `to_string` method is also used on other types to convert them to a string.
372 /// When called on a `&str` it turns the `&str` into the owned variant `String`, which can be better
373 /// expressed with `.to_owned()`.
377 /// // example code where clippy issues a warning
378 /// let _ = "str".to_string();
382 /// // example code which does not raise clippy warning
383 /// let _ = "str".to_owned();
385 #[clippy::version = "pre 1.29.0"]
388 "using `to_string()` on a `&str`, which should be `to_owned()`"
391 declare_lint_pass
!(StrToString
=> [STR_TO_STRING
]);
393 impl<'tcx
> LateLintPass
<'tcx
> for StrToString
{
394 fn check_expr(&mut self, cx
: &LateContext
<'tcx
>, expr
: &Expr
<'_
>) {
396 if let ExprKind
::MethodCall(path
, [self_arg
, ..], _
) = &expr
.kind
;
397 if path
.ident
.name
== sym
::to_string
;
398 let ty
= cx
.typeck_results().expr_ty(self_arg
);
399 if let ty
::Ref(_
, ty
, ..) = ty
.kind();
400 if *ty
.kind() == ty
::Str
;
406 "`to_string()` called on a `&str`",
408 "consider using `.to_owned()`",
415 declare_clippy_lint
! {
417 /// This lint checks for `.to_string()` method calls on values of type `String`.
419 /// ### Why is this bad?
420 /// The `to_string` method is also used on other types to convert them to a string.
421 /// When called on a `String` it only clones the `String`, which can be better expressed with `.clone()`.
425 /// // example code where clippy issues a warning
426 /// let msg = String::from("Hello World");
427 /// let _ = msg.to_string();
431 /// // example code which does not raise clippy warning
432 /// let msg = String::from("Hello World");
433 /// let _ = msg.clone();
435 #[clippy::version = "pre 1.29.0"]
436 pub STRING_TO_STRING
,
438 "using `to_string()` on a `String`, which should be `clone()`"
441 declare_lint_pass
!(StringToString
=> [STRING_TO_STRING
]);
443 impl<'tcx
> LateLintPass
<'tcx
> for StringToString
{
444 fn check_expr(&mut self, cx
: &LateContext
<'tcx
>, expr
: &Expr
<'_
>) {
446 if let ExprKind
::MethodCall(path
, [self_arg
, ..], _
) = &expr
.kind
;
447 if path
.ident
.name
== sym
::to_string
;
448 let ty
= cx
.typeck_results().expr_ty(self_arg
);
449 if is_type_diagnostic_item(cx
, ty
, sym
::String
);
455 "`to_string()` called on a `String`",
457 "consider using `.clone()`",
464 declare_clippy_lint
! {
466 /// Warns about calling `str::trim` (or variants) before `str::split_whitespace`.
468 /// ### Why is this bad?
469 /// `split_whitespace` already ignores leading and trailing whitespace.
473 /// " A B C ".trim().split_whitespace();
477 /// " A B C ".split_whitespace();
479 #[clippy::version = "1.62.0"]
480 pub TRIM_SPLIT_WHITESPACE
,
482 "using `str::trim()` or alike before `str::split_whitespace`"
484 declare_lint_pass
!(TrimSplitWhitespace
=> [TRIM_SPLIT_WHITESPACE
]);
486 impl<'tcx
> LateLintPass
<'tcx
> for TrimSplitWhitespace
{
487 fn check_expr(&mut self, cx
: &LateContext
<'tcx
>, expr
: &Expr
<'_
>) {
488 let tyckres
= cx
.typeck_results();
490 if let ExprKind
::MethodCall(path
, [split_recv
], split_ws_span
) = expr
.kind
;
491 if path
.ident
.name
== sym
!(split_whitespace
);
492 if let Some(split_ws_def_id
) = tyckres
.type_dependent_def_id(expr
.hir_id
);
493 if cx
.tcx
.is_diagnostic_item(sym
::str_split_whitespace
, split_ws_def_id
);
494 if let ExprKind
::MethodCall(path
, [_trim_recv
], trim_span
) = split_recv
.kind
;
495 if let trim_fn_name @
("trim" | "trim_start" | "trim_end") = path
.ident
.name
.as_str();
496 if let Some(trim_def_id
) = tyckres
.type_dependent_def_id(split_recv
.hir_id
);
497 if is_one_of_trim_diagnostic_items(cx
, trim_def_id
);
501 TRIM_SPLIT_WHITESPACE
,
502 trim_span
.with_hi(split_ws_span
.lo()),
503 &format
!("found call to `str::{}` before `str::split_whitespace`", trim_fn_name
),
504 &format
!("remove `{}()`", trim_fn_name
),
506 Applicability
::MachineApplicable
,
513 fn is_one_of_trim_diagnostic_items(cx
: &LateContext
<'_
>, trim_def_id
: DefId
) -> bool
{
514 cx
.tcx
.is_diagnostic_item(sym
::str_trim
, trim_def_id
)
515 || cx
.tcx
.is_diagnostic_item(sym
::str_trim_start
, trim_def_id
)
516 || cx
.tcx
.is_diagnostic_item(sym
::str_trim_end
, trim_def_id
)