Add lint for "string literal".as_bytes()

This commit is contained in:
Florian Hartwig 2016-01-19 19:14:49 +01:00
parent a0496f08ca
commit 01eda52cb5
4 changed files with 61 additions and 1 deletions

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@ -6,7 +6,7 @@ A collection of lints to catch common mistakes and improve your Rust code.
[Jump to usage instructions](#usage)
##Lints
There are 93 lints included in this crate:
There are 94 lints included in this crate:
name | default | meaning
---------------------------------------------------------------------------------------------------------------|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
@ -83,6 +83,7 @@ name
[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()`
[string_add](https://github.com/Manishearth/rust-clippy/wiki#string_add) | allow | using `x + ..` where x is a `String`; suggests using `push_str()` instead
[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
[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
[string_to_string](https://github.com/Manishearth/rust-clippy/wiki#string_to_string) | warn | calling `String.to_string()` which is a no-op
[temporary_assignment](https://github.com/Manishearth/rust-clippy/wiki#temporary_assignment) | warn | assignments to temporaries
[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) {
reg.register_late_lint_pass(box misc::UsedUnderscoreBinding);
reg.register_late_lint_pass(box array_indexing::ArrayIndexing);
reg.register_late_lint_pass(box panic::PanicPass);
reg.register_late_lint_pass(box strings::StringLitAsBytes);
reg.register_lint_group("clippy_pedantic", vec![
@ -225,6 +226,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
ranges::RANGE_ZIP_WITH_LEN,
returns::LET_AND_RETURN,
returns::NEEDLESS_RETURN,
strings::STRING_LIT_AS_BYTES,
temporary_assignment::TEMPORARY_ASSIGNMENT,
transmute::USELESS_TRANSMUTE,
types::BOX_VEC,

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@ -48,6 +48,22 @@ declare_lint! {
"using `x + ..` where x is a `String`; suggests using `push_str()` instead"
}
/// **What it does:** This lint matches the `as_bytes` method called on string
/// literals that contain only ascii characters. It is `Warn` by default.
///
/// **Why is this bad?** Byte string literals (e.g. `b"foo"`) can be used instead. They are shorter but less discoverable than `as_bytes()`.
///
/// **Example:**
///
/// ```
/// let bs = "a byte string".as_bytes();
/// ```
declare_lint! {
pub STRING_LIT_AS_BYTES,
Warn,
"calling `as_bytes` on a string literal; suggests using a byte string literal instead"
}
#[derive(Copy, Clone)]
pub struct StringAdd;
@ -104,3 +120,36 @@ fn is_add(cx: &LateContext, src: &Expr, target: &Expr) -> bool {
_ => false,
}
}
#[derive(Copy, Clone)]
pub struct StringLitAsBytes;
impl LintPass for StringLitAsBytes {
fn get_lints(&self) -> LintArray {
lint_array!(STRING_LIT_AS_BYTES)
}
}
impl LateLintPass for StringLitAsBytes {
fn check_expr(&mut self, cx: &LateContext, e: &Expr) {
use std::ascii::AsciiExt;
use syntax::ast::Lit_::LitStr;
use utils::snippet;
if let ExprMethodCall(ref name, _, ref args) = e.node {
if name.node.as_str() == "as_bytes" {
if let ExprLit(ref lit) = args[0].node {
if let LitStr(ref lit_content, _) = lit.node {
if lit_content.chars().all(|c| c.is_ascii()) {
let msg = format!("calling `as_bytes()` on a string literal. \
Consider using a byte string literal instead: \
`b{}`",
snippet(cx, args[0].span, r#""foo""#));
span_lint(cx, STRING_LIT_AS_BYTES, e.span, &msg);
}
}
}
}
}
}
}

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@ -44,6 +44,14 @@ fn both() {
assert_eq!(&x, &z);
}
#[allow(dead_code, unused_variables)]
#[deny(string_lit_as_bytes)]
fn str_lit_as_bytes() {
let bs = "hello there".as_bytes(); //~ERROR calling `as_bytes()`
// no warning, because this cannot be written as a byte string literal:
let ubs = "".as_bytes();
}
fn main() {
add_only();
add_assign_only();