Add string_from_utf8_as_bytes linter

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>
This commit is contained in:
Patrick José Pereira 2020-10-08 00:19:56 -03:00
parent e298c830af
commit bc27d1492d
8 changed files with 99 additions and 3 deletions

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@ -1952,6 +1952,7 @@ Released 2018-09-13
[`string_add`]: https://rust-lang.github.io/rust-clippy/master/index.html#string_add
[`string_add_assign`]: https://rust-lang.github.io/rust-clippy/master/index.html#string_add_assign
[`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_to_string`]: https://rust-lang.github.io/rust-clippy/master/index.html#string_to_string
[`struct_excessive_bools`]: https://rust-lang.github.io/rust-clippy/master/index.html#struct_excessive_bools

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@ -826,6 +826,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
&stable_sort_primitive::STABLE_SORT_PRIMITIVE,
&strings::STRING_ADD,
&strings::STRING_ADD_ASSIGN,
&strings::STRING_FROM_UTF8_AS_BYTES,
&strings::STRING_LIT_AS_BYTES,
&suspicious_trait_impl::SUSPICIOUS_ARITHMETIC_IMPL,
&suspicious_trait_impl::SUSPICIOUS_OP_ASSIGN_IMPL,
@ -1515,6 +1516,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
LintId::of(&single_component_path_imports::SINGLE_COMPONENT_PATH_IMPORTS),
LintId::of(&slow_vector_initialization::SLOW_VECTOR_INITIALIZATION),
LintId::of(&stable_sort_primitive::STABLE_SORT_PRIMITIVE),
LintId::of(&strings::STRING_FROM_UTF8_AS_BYTES),
LintId::of(&suspicious_trait_impl::SUSPICIOUS_ARITHMETIC_IMPL),
LintId::of(&suspicious_trait_impl::SUSPICIOUS_OP_ASSIGN_IMPL),
LintId::of(&swap::ALMOST_SWAPPED),
@ -1738,6 +1740,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
LintId::of(&reference::DEREF_ADDROF),
LintId::of(&reference::REF_IN_DEREF),
LintId::of(&repeat_once::REPEAT_ONCE),
LintId::of(&strings::STRING_FROM_UTF8_AS_BYTES),
LintId::of(&swap::MANUAL_SWAP),
LintId::of(&temporary_assignment::TEMPORARY_ASSIGNMENT),
LintId::of(&transmute::CROSSPOINTER_TRANSMUTE),

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@ -1,5 +1,5 @@
use rustc_errors::Applicability;
use rustc_hir::{BinOpKind, Expr, ExprKind};
use rustc_hir::{BinOpKind, BorrowKind, Expr, ExprKind, LangItem, QPath};
use rustc_lint::{LateContext, LateLintPass, LintContext};
use rustc_middle::lint::in_external_macro;
use rustc_session::{declare_lint_pass, declare_tool_lint};
@ -8,7 +8,10 @@ use rustc_span::source_map::Spanned;
use if_chain::if_chain;
use crate::utils::SpanlessEq;
use crate::utils::{get_parent_expr, is_allowed, is_type_diagnostic_item, span_lint, span_lint_and_sugg};
use crate::utils::{
get_parent_expr, is_allowed, is_type_diagnostic_item, match_function_call, method_calls, paths, span_lint,
span_lint_and_sugg,
};
declare_clippy_lint! {
/// **What it does:** Checks for string appends of the form `x = x + y` (without
@ -173,16 +176,75 @@ fn is_add(cx: &LateContext<'_>, src: &Expr<'_>, target: &Expr<'_>) -> bool {
}
}
declare_clippy_lint! {
/// **What it does:** Check if the string is transformed to byte array and casted back to string.
///
/// **Why is this bad?** It's unnecessary, the string can be used directly.
///
/// **Known problems:** None
///
/// **Example:**
/// ```rust
/// let _ = std::str::from_utf8(&"Hello World!".as_bytes()[6..11]).unwrap();
/// ```
/// could be written as
/// ```rust
/// let _ = &"Hello World!"[6..11];
/// ```
pub STRING_FROM_UTF8_AS_BYTES,
complexity,
"casting string slices to byte slices and back"
}
// Max length a b"foo" string can take
const MAX_LENGTH_BYTE_STRING_LIT: usize = 32;
declare_lint_pass!(StringLitAsBytes => [STRING_LIT_AS_BYTES]);
declare_lint_pass!(StringLitAsBytes => [STRING_LIT_AS_BYTES, STRING_FROM_UTF8_AS_BYTES]);
impl<'tcx> LateLintPass<'tcx> for StringLitAsBytes {
fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
use crate::utils::{snippet, snippet_with_applicability};
use rustc_ast::LitKind;
if_chain! {
// Find std::str::converts::from_utf8
if let Some(args) = match_function_call(cx, e, &paths::STR_FROM_UTF8);
// Find string::as_bytes
if let ExprKind::AddrOf(BorrowKind::Ref, _, ref args) = args[0].kind;
if let ExprKind::Index(ref left, ref right) = args.kind;
let (method_names, expressions, _) = method_calls(left, 1);
if method_names.len() == 1;
if expressions.len() == 1;
if expressions[0].len() == 1;
if method_names[0] == sym!(as_bytes);
// Check for slicer
if let ExprKind::Struct(ref path, _, _) = right.kind;
if let QPath::LangItem(LangItem::Range, _) = path;
then {
let mut applicability = Applicability::MachineApplicable;
let string_expression = &expressions[0][0];
let snippet_app = snippet_with_applicability(
cx,
string_expression.span, "..",
&mut applicability,
);
span_lint_and_sugg(
cx,
STRING_FROM_UTF8_AS_BYTES,
e.span,
"calling a slice of `as_bytes()` with `from_utf8` should be not necessary",
"try",
format!("Some(&{}[{}])", snippet_app, snippet(cx, right.span, "..")),
applicability
)
}
}
if_chain! {
if let ExprKind::MethodCall(path, _, args, _) = &e.kind;
if path.ident.name == sym!(as_bytes);

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@ -120,6 +120,7 @@ pub const STRING: [&str; 3] = ["alloc", "string", "String"];
pub const STRING_AS_MUT_STR: [&str; 4] = ["alloc", "string", "String", "as_mut_str"];
pub const STRING_AS_STR: [&str; 4] = ["alloc", "string", "String", "as_str"];
pub const STR_ENDS_WITH: [&str; 4] = ["core", "str", "<impl str>", "ends_with"];
pub const STR_FROM_UTF8: [&str; 4] = ["core", "str", "converts", "from_utf8"];
pub const STR_LEN: [&str; 4] = ["core", "str", "<impl str>", "len"];
pub const STR_STARTS_WITH: [&str; 4] = ["core", "str", "<impl str>", "starts_with"];
pub const SYNTAX_CONTEXT: [&str; 3] = ["rustc_span", "hygiene", "SyntaxContext"];

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@ -2230,6 +2230,13 @@ vec![
deprecation: None,
module: "methods",
},
Lint {
name: "string_from_utf8_as_bytes",
group: "complexity",
desc: "casting string slices to byte slices and back",
deprecation: None,
module: "strings",
},
Lint {
name: "string_lit_as_bytes",
group: "nursery",

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@ -0,0 +1,6 @@
// run-rustfix
#![warn(clippy::string_from_utf8_as_bytes)]
fn main() {
let _ = Some(&"Hello World!"[6..11]);
}

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@ -0,0 +1,6 @@
// run-rustfix
#![warn(clippy::string_from_utf8_as_bytes)]
fn main() {
let _ = std::str::from_utf8(&"Hello World!".as_bytes()[6..11]);
}

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@ -0,0 +1,10 @@
error: calling a slice of `as_bytes()` with `from_utf8` should be not necessary
--> $DIR/string_from_utf8_as_bytes.rs:5:13
|
LL | let _ = std::str::from_utf8(&"Hello World!".as_bytes()[6..11]);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `Some(&"Hello World!"[6..11])`
|
= note: `-D clippy::string-from-utf8-as-bytes` implied by `-D warnings`
error: aborting due to previous error