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Auto merge of #7878 - rust-lang:string-slice, r=giraffate

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new lint: string-slice

This is a restriction lint to highlight code that should have tests containing non-ascii characters. See #6623.

changelog: new lint: [`string-slice`]
This commit is contained in:
bors 2021-10-26 08:11:49 +00:00
commit 075996efd7
6 changed files with 106 additions and 35 deletions
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1
CHANGELOG.md
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@ -3147,6 +3147,7 @@ Released 2018-09-13
[`string_extend_chars`]: https://rust-lang.github.io/rust-clippy/master/index.html#string_extend_chars
[`string_from_utf8_as_bytes`]: https://rust-lang.github.io/rust-clippy/master/index.html#string_from_utf8_as_bytes
[`string_lit_as_bytes`]: https://rust-lang.github.io/rust-clippy/master/index.html#string_lit_as_bytes
[`string_slice`]: https://rust-lang.github.io/rust-clippy/master/index.html#string_slice
[`string_to_string`]: https://rust-lang.github.io/rust-clippy/master/index.html#string_to_string
[`strlen_on_c_strings`]: https://rust-lang.github.io/rust-clippy/master/index.html#strlen_on_c_strings
[`struct_excessive_bools`]: https://rust-lang.github.io/rust-clippy/master/index.html#struct_excessive_bools

1
clippy_lints/src/lib.register_lints.rs
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@ -431,6 +431,7 @@
strings::STRING_ADD_ASSIGN,
strings::STRING_FROM_UTF8_AS_BYTES,
strings::STRING_LIT_AS_BYTES,
strings::STRING_SLICE,
strings::STRING_TO_STRING,
strings::STR_TO_STRING,
strlen_on_c_strings::STRLEN_ON_C_STRINGS,

1
clippy_lints/src/lib.register_restriction.rs
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@ -53,6 +53,7 @@
LintId::of(shadow::SHADOW_SAME),
LintId::of(shadow::SHADOW_UNRELATED),
LintId::of(strings::STRING_ADD),
LintId::of(strings::STRING_SLICE),
LintId::of(strings::STRING_TO_STRING),
LintId::of(strings::STR_TO_STRING),
LintId::of(types::RC_BUFFER),

106
clippy_lints/src/strings.rs
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@ -107,51 +107,87 @@
"calling `as_bytes` on a string literal instead of using a byte string literal"
}
declare_lint_pass!(StringAdd => [STRING_ADD, STRING_ADD_ASSIGN]);
declare_clippy_lint! {
/// ### What it does
/// Checks for slice operations on strings
///
/// ### Why is this bad?
/// UTF-8 characters span multiple bytes, and it is easy to inadvertently confuse character
/// counts and string indices. This may lead to panics, and should warrant some test cases
/// containing wide UTF-8 characters. This lint is most useful in code that should avoid
/// panics at all costs.
///
/// ### Known problems
/// Probably lots of false positives. If an index comes from a known valid position (e.g.
/// obtained via `char_indices` over the same string), it is totally OK.
///
/// # Example
/// ```rust,should_panic
/// &"Ölkanne"[1..];
/// ```
pub STRING_SLICE,
restriction,
"slicing a string"
}
declare_lint_pass!(StringAdd => [STRING_ADD, STRING_ADD_ASSIGN, STRING_SLICE]);
impl<'tcx> LateLintPass<'tcx> for StringAdd {
fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
if in_external_macro(cx.sess(), e.span) {
return;
}
if let ExprKind::Binary(
Spanned {
node: BinOpKind::Add, ..
},
left,
_,
) = e.kind
{
if is_string(cx, left) {
if !is_lint_allowed(cx, STRING_ADD_ASSIGN, e.hir_id) {
let parent = get_parent_expr(cx, e);
if let Some(p) = parent {
if let ExprKind::Assign(target, _, _) = p.kind {
// avoid duplicate matches
if SpanlessEq::new(cx).eq_expr(target, left) {
return;
match e.kind {
ExprKind::Binary(
Spanned {
node: BinOpKind::Add, ..
},
left,
_,
) => {
if is_string(cx, left) {
if !is_lint_allowed(cx, STRING_ADD_ASSIGN, e.hir_id) {
let parent = get_parent_expr(cx, e);
if let Some(p) = parent {
if let ExprKind::Assign(target, _, _) = p.kind {
// avoid duplicate matches
if SpanlessEq::new(cx).eq_expr(target, left) {
return;
}
}
}
}
span_lint(
cx,
STRING_ADD,
e.span,
"you added something to a string. Consider using `String::push_str()` instead",
);
}
span_lint(
cx,
STRING_ADD,
e.span,
"you added something to a string. Consider using `String::push_str()` instead",
);
}
} else if let ExprKind::Assign(target, src, _) = e.kind {
if is_string(cx, target) && is_add(cx, src, target) {
span_lint(
cx,
STRING_ADD_ASSIGN,
e.span,
"you assigned the result of adding something to this string. Consider using \
`String::push_str()` instead",
);
}
},
ExprKind::Assign(target, src, _) => {
if is_string(cx, target) && is_add(cx, src, target) {
span_lint(
cx,
STRING_ADD_ASSIGN,
e.span,
"you assigned the result of adding something to this string. Consider using \
`String::push_str()` instead",
);
}
},
ExprKind::Index(target, _idx) => {
let e_ty = cx.typeck_results().expr_ty(target).peel_refs();
if matches!(e_ty.kind(), ty::Str) || is_type_diagnostic_item(cx, e_ty, sym::String) {
span_lint(
cx,
STRING_SLICE,
e.span,
"indexing into a string may panic if the index is within a UTF-8 character",
);
}
},
_ => {},
}
}
}

10
tests/ui/string_slice.rs Normal file
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@ -0,0 +1,10 @@
#[warn(clippy::string_slice)]
#[allow(clippy::no_effect)]
fn main() {
&"Ölkanne"[1..];
let m = "Mötörhead";
&m[2..5];
let s = String::from(m);
&s[0..2];
}

22
tests/ui/string_slice.stderr Normal file
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@ -0,0 +1,22 @@
error: indexing into a string may panic if the index is within a UTF-8 character
--> $DIR/string_slice.rs:5:6
|
LL | &"Ölkanne"[1..];
| ^^^^^^^^^^^^^^
|
= note: `-D clippy::string-slice` implied by `-D warnings`
error: indexing into a string may panic if the index is within a UTF-8 character
--> $DIR/string_slice.rs:7:6
|
LL | &m[2..5];
| ^^^^^^^
error: indexing into a string may panic if the index is within a UTF-8 character
--> $DIR/string_slice.rs:9:6
|
LL | &s[0..2];
| ^^^^^^^
error: aborting due to 3 previous errors