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https://github.com/rust-lang/rust-clippy
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Add lint for "string literal".as_bytes()
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@ -6,7 +6,7 @@ A collection of lints to catch common mistakes and improve your Rust code.
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[Jump to usage instructions](#usage)
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##Lints
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There are 93 lints included in this crate:
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There are 94 lints included in this crate:
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name | default | meaning
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---------------------------------------------------------------------------------------------------------------|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
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@ -83,6 +83,7 @@ name
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[str_to_string](https://github.com/Manishearth/rust-clippy/wiki#str_to_string) | warn | using `to_string()` on a str, which should be `to_owned()`
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[string_add](https://github.com/Manishearth/rust-clippy/wiki#string_add) | allow | using `x + ..` where x is a `String`; suggests using `push_str()` instead
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[string_add_assign](https://github.com/Manishearth/rust-clippy/wiki#string_add_assign) | allow | using `x = x + ..` where x is a `String`; suggests using `push_str()` instead
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[string_lit_as_bytes](https://github.com/Manishearth/rust-clippy/wiki#string_lit_as_bytes) | warn | calling `as_bytes` on a string literal; suggests using a byte string literal instead
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[string_to_string](https://github.com/Manishearth/rust-clippy/wiki#string_to_string) | warn | calling `String.to_string()` which is a no-op
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[temporary_assignment](https://github.com/Manishearth/rust-clippy/wiki#temporary_assignment) | warn | assignments to temporaries
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[toplevel_ref_arg](https://github.com/Manishearth/rust-clippy/wiki#toplevel_ref_arg) | warn | An entire binding was declared as `ref`, in a function argument (`fn foo(ref x: Bar)`), or a `let` statement (`let ref x = foo()`). In such cases, it is preferred to take references with `&`.
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@ -135,6 +135,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
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reg.register_late_lint_pass(box misc::UsedUnderscoreBinding);
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reg.register_late_lint_pass(box array_indexing::ArrayIndexing);
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reg.register_late_lint_pass(box panic::PanicPass);
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reg.register_late_lint_pass(box strings::StringLitAsBytes);
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reg.register_lint_group("clippy_pedantic", vec![
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@ -225,6 +226,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
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ranges::RANGE_ZIP_WITH_LEN,
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returns::LET_AND_RETURN,
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returns::NEEDLESS_RETURN,
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strings::STRING_LIT_AS_BYTES,
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temporary_assignment::TEMPORARY_ASSIGNMENT,
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transmute::USELESS_TRANSMUTE,
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types::BOX_VEC,
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@ -48,6 +48,22 @@ declare_lint! {
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"using `x + ..` where x is a `String`; suggests using `push_str()` instead"
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}
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/// **What it does:** This lint matches the `as_bytes` method called on string
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/// literals that contain only ascii characters. It is `Warn` by default.
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///
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/// **Why is this bad?** Byte string literals (e.g. `b"foo"`) can be used instead. They are shorter but less discoverable than `as_bytes()`.
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///
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/// **Example:**
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///
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/// ```
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/// let bs = "a byte string".as_bytes();
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/// ```
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declare_lint! {
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pub STRING_LIT_AS_BYTES,
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Warn,
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"calling `as_bytes` on a string literal; suggests using a byte string literal instead"
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}
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#[derive(Copy, Clone)]
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pub struct StringAdd;
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@ -104,3 +120,36 @@ fn is_add(cx: &LateContext, src: &Expr, target: &Expr) -> bool {
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_ => false,
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}
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}
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#[derive(Copy, Clone)]
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pub struct StringLitAsBytes;
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impl LintPass for StringLitAsBytes {
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fn get_lints(&self) -> LintArray {
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lint_array!(STRING_LIT_AS_BYTES)
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}
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}
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impl LateLintPass for StringLitAsBytes {
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fn check_expr(&mut self, cx: &LateContext, e: &Expr) {
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use std::ascii::AsciiExt;
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use syntax::ast::Lit_::LitStr;
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use utils::snippet;
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if let ExprMethodCall(ref name, _, ref args) = e.node {
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if name.node.as_str() == "as_bytes" {
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if let ExprLit(ref lit) = args[0].node {
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if let LitStr(ref lit_content, _) = lit.node {
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if lit_content.chars().all(|c| c.is_ascii()) {
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let msg = format!("calling `as_bytes()` on a string literal. \
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Consider using a byte string literal instead: \
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`b{}`",
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snippet(cx, args[0].span, r#""foo""#));
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span_lint(cx, STRING_LIT_AS_BYTES, e.span, &msg);
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}
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}
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}
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}
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}
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}
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}
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@ -44,6 +44,14 @@ fn both() {
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assert_eq!(&x, &z);
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}
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#[allow(dead_code, unused_variables)]
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#[deny(string_lit_as_bytes)]
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fn str_lit_as_bytes() {
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let bs = "hello there".as_bytes(); //~ERROR calling `as_bytes()`
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// no warning, because this cannot be written as a byte string literal:
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let ubs = "☃".as_bytes();
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}
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fn main() {
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add_only();
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add_assign_only();
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