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https://github.com/rust-lang/rust-clippy
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Lint about usage of format!("string literal")
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4 changed files with 55 additions and 1 deletions
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@ -8,7 +8,7 @@ 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 122 lints included in this crate:
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There are 123 lints included in this crate:
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name | default | meaning
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---------------------------------------------------------------------------------------------------------------|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
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@ -126,6 +126,7 @@ name
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[unused_lifetimes](https://github.com/Manishearth/rust-clippy/wiki#unused_lifetimes) | warn | unused lifetimes in function definitions
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[use_debug](https://github.com/Manishearth/rust-clippy/wiki#use_debug) | allow | use `Debug`-based formatting
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[used_underscore_binding](https://github.com/Manishearth/rust-clippy/wiki#used_underscore_binding) | warn | using a binding which is prefixed with an underscore
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[useless_format](https://github.com/Manishearth/rust-clippy/wiki#useless_format) | warn | useless use of `format!`
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[useless_transmute](https://github.com/Manishearth/rust-clippy/wiki#useless_transmute) | warn | transmutes that have the same to and from types
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[useless_vec](https://github.com/Manishearth/rust-clippy/wiki#useless_vec) | warn | useless `vec!`
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[while_let_loop](https://github.com/Manishearth/rust-clippy/wiki#while_let_loop) | warn | `loop { if let { ... } else break }` can be written as a `while let` loop
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40
src/format.rs
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40
src/format.rs
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@ -0,0 +1,40 @@
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use rustc::lint::*;
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use rustc_front::hir::*;
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use utils::{is_expn_of, span_lint};
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/// **What it does:** This lints about use of `format!("string literal with no argument")`.
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///
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/// **Why is this bad?** There is no point of doing that. If you want a `String` you can use
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/// `to_owned` on the string literal. The even worst `&format!("foo")` is often encountered in the
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/// wild.
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///
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/// **Known problems:** None.
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///
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/// **Example:** `format!("foo")`
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declare_lint! {
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pub USELESS_FORMAT,
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Warn,
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"useless use of `format!`"
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}
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#[derive(Copy, Clone, Debug)]
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pub struct FormatMacLint;
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impl LintPass for FormatMacLint {
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fn get_lints(&self) -> LintArray {
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lint_array![USELESS_FORMAT]
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}
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}
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impl LateLintPass for FormatMacLint {
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fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
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// `format!("foo")` expansion contains `match () { () => [], }`
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if let ExprMatch(ref matchee, _, _) = expr.node {
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if let ExprTup(ref tup) = matchee.node {
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if tup.is_empty() && is_expn_of(cx, expr.span, "format").is_some() {
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span_lint(cx, USELESS_FORMAT, expr.span, &"useless use of `format!`");
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}
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}
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}
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}
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}
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@ -163,6 +163,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
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reg.register_late_lint_pass(box types::AbsurdExtremeComparisons);
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reg.register_late_lint_pass(box regex::RegexPass::default());
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reg.register_late_lint_pass(box copies::CopyAndPaste);
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reg.register_late_lint_pass(box format::FormatMacLint);
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reg.register_lint_group("clippy_pedantic", vec![
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enum_glob_use::ENUM_GLOB_USE,
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@ -209,6 +210,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
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eq_op::EQ_OP,
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escape::BOXED_LOCAL,
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eta_reduction::REDUNDANT_CLOSURE,
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format::USELESS_FORMAT,
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identity_op::IDENTITY_OP,
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items_after_statements::ITEMS_AFTER_STATEMENTS,
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len_zero::LEN_WITHOUT_IS_EMPTY,
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11
tests/compile-fail/format.rs
Executable file
11
tests/compile-fail/format.rs
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#![feature(plugin)]
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#![plugin(clippy)]
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#![deny(useless_format)]
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fn main() {
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format!("foo"); //~ERROR useless use of `format!`
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format!("foo {}", 42);
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println!("foo");
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println!("foo {}", 42);
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}
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