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Merge pull request #669 from shssoichiro/single-char-pattern 

Lint single-character strings as P: Pattern args
This commit is contained in:
llogiq 2016-02-16 14:24:22 +01:00
parent 09ef38b30b b1e4b496e1
commit 59c8f6210b
5 changed files with 158 additions and 4 deletions
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3
README.md
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@ -8,7 +8,7 @@ A collection of lints to catch common mistakes and improve your Rust code.
[Jump to usage instructions](#usage)
##Lints
There are 121 lints included in this crate:
There are 122 lints included in this crate:
name | default | meaning
---------------------------------------------------------------------------------------------------------------|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
@ -104,6 +104,7 @@ name
[shadow_same](https://github.com/Manishearth/rust-clippy/wiki#shadow_same) | allow | rebinding a name to itself, e.g. `let mut x = &mut x`
[shadow_unrelated](https://github.com/Manishearth/rust-clippy/wiki#shadow_unrelated) | allow | The name is re-bound without even using the original value
[should_implement_trait](https://github.com/Manishearth/rust-clippy/wiki#should_implement_trait) | warn | defining a method that should be implementing a std trait
[single_char_pattern](https://github.com/Manishearth/rust-clippy/wiki#single_char_pattern) | warn | using a single-character str where a char could be used, e.g. `_.split("x")`
[single_match](https://github.com/Manishearth/rust-clippy/wiki#single_match) | warn | a match statement with a single nontrivial arm (i.e, where the other arm is `_ => {}`) is used; recommends `if let` instead
[single_match_else](https://github.com/Manishearth/rust-clippy/wiki#single_match_else) | allow | a match statement with a two arms where the second arm's pattern is a wildcard; recommends `if let` instead
[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()`

1
src/lib.rs
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@ -241,6 +241,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
methods::OR_FUN_CALL,
methods::SEARCH_IS_SOME,
methods::SHOULD_IMPLEMENT_TRAIT,
methods::SINGLE_CHAR_PATTERN,
methods::STR_TO_STRING,
methods::STRING_TO_STRING,
methods::WRONG_SELF_CONVENTION,

62
src/methods.rs
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@ -1,4 +1,6 @@
use rustc::lint::*;
use rustc::middle::const_eval::{ConstVal, eval_const_expr_partial};
use rustc::middle::const_eval::EvalHint::ExprTypeChecked;
use rustc::middle::subst::{Subst, TypeSpace};
use rustc::middle::ty;
use rustc_front::hir::*;
@ -295,6 +297,20 @@ declare_lint! {
pub NEW_RET_NO_SELF, Warn, "not returning `Self` in a `new` method"
}
/// **What it does:** This lint checks for string methods that receive a single-character `str` as an argument, e.g. `_.split("x")`.
///
/// **Why is this bad?** Performing these methods using a `char` is faster than using a `str`.
///
/// **Known problems:** Does not catch multi-byte unicode characters.
///
/// **Example:** `_.split("x")` could be `_.split('x')`
declare_lint! {
pub SINGLE_CHAR_PATTERN,
Warn,
"using a single-character str where a char could be used, e.g. \
`_.split(\"x\")`"
}
impl LintPass for MethodsPass {
fn get_lints(&self) -> LintArray {
lint_array!(EXTEND_FROM_SLICE,
@ -312,7 +328,8 @@ impl LintPass for MethodsPass {
CHARS_NEXT_CMP,
CLONE_ON_COPY,
CLONE_DOUBLE_REF,
NEW_RET_NO_SELF)
NEW_RET_NO_SELF,
SINGLE_CHAR_PATTERN)
}
}
@ -351,6 +368,11 @@ impl LateLintPass for MethodsPass {
lint_clone_on_copy(cx, expr);
lint_clone_double_ref(cx, expr, &args[0]);
}
for &(method, pos) in &PATTERN_METHODS {
if name.node.as_str() == method && args.len() > pos {
lint_single_char_pattern(cx, expr, &args[pos]);
}
}
}
ExprBinary(op, ref lhs, ref rhs) if op.node == BiEq || op.node == BiNe => {
if !lint_chars_next(cx, expr, lhs, rhs, op.node == BiEq) {
@ -819,6 +841,22 @@ fn lint_chars_next(cx: &LateContext, expr: &Expr, chain: &Expr, other: &Expr, eq
false
}
/// lint for length-1 `str`s for methods in `PATTERN_METHODS`
fn lint_single_char_pattern(cx: &LateContext, expr: &Expr, arg: &Expr) {
if let Ok(ConstVal::Str(r)) = eval_const_expr_partial(cx.tcx, arg, ExprTypeChecked, None) {
if r.len() == 1 {
let hint = snippet(cx, expr.span, "..").replace(&format!("\"{}\"", r), &format!("'{}'", r));
span_lint_and_then(cx,
SINGLE_CHAR_PATTERN,
arg.span,
"single-character string constant used as pattern",
|db| {
db.span_suggestion(expr.span, "try using a char instead:", hint);
});
}
}
}
/// Given a `Result<T, E>` type, return its error type (`E`).
fn get_error_type<'a>(cx: &LateContext, ty: ty::Ty<'a>) -> Option<ty::Ty<'a>> {
if !match_type(cx, ty, &RESULT_PATH) {
@ -889,6 +927,28 @@ const TRAIT_METHODS: [(&'static str, usize, SelfKind, OutType, &'static str); 30
("sub", 2, SelfKind::Value, OutType::Any, "std::ops::Sub"),
];
#[cfg_attr(rustfmt, rustfmt_skip)]
const PATTERN_METHODS: [(&'static str, usize); 17] = [
("contains", 1),
("starts_with", 1),
("ends_with", 1),
("find", 1),
("rfind", 1),
("split", 1),
("rsplit", 1),
("split_terminator", 1),
("rsplit_terminator", 1),
("splitn", 2),
("rsplitn", 2),
("matches", 1),
("rmatches", 1),
("match_indices", 1),
("rmatch_indices", 1),
("trim_left_matches", 1),
("trim_right_matches", 1),
];
#[derive(Clone, Copy)]
enum SelfKind {
Value,

2
src/misc_early.rs
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@ -104,7 +104,7 @@ impl EarlyLintPass for MiscEarly {
if let PatIdent(_, sp_ident, None) = arg.pat.node {
let arg_name = sp_ident.node.to_string();
if arg_name.starts_with("_") {
if arg_name.starts_with('_') {
if let Some(correspondance) = registered_names.get(&arg_name[1..]) {
span_lint(cx,
DUPLICATE_UNDERSCORE_ARGUMENT,

94
tests/compile-fail/methods.rs
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@ -2,7 +2,7 @@
#![plugin(clippy)]
#![deny(clippy, clippy_pedantic)]
#![allow(unused, print_stdout)]
#![allow(unused, print_stdout, non_ascii_literal)]
use std::collections::BTreeMap;
use std::collections::HashMap;
@ -355,3 +355,95 @@ fn clone_on_double_ref() {
//~^^^ERROR using `clone` on a `Copy` type
println!("{:p} {:p}",*y, z);
}
fn single_char_pattern() {
let x = "foo";
x.split("x");
//~^ ERROR single-character string constant used as pattern
//~| HELP try using a char instead:
//~| SUGGESTION x.split('x');
x.split("xx");
x.split('x');
let y = "x";
x.split(y);
// Not yet testing for multi-byte characters
// Changing `r.len() == 1` to `r.chars().count() == 1` in `lint_single_char_pattern`
// should have done this but produced an ICE
//
// We may not want to suggest changing these anyway
// See: https://github.com/Manishearth/rust-clippy/issues/650#issuecomment-184328984
x.split("ß");
x.split("ℝ");
x.split("💣");
// Can't use this lint for unicode code points which don't fit in a char
x.split("❤️");
x.contains("x");
//~^ ERROR single-character string constant used as pattern
//~| HELP try using a char instead:
//~| SUGGESTION x.contains('x');
x.starts_with("x");
//~^ ERROR single-character string constant used as pattern
//~| HELP try using a char instead:
//~| SUGGESTION x.starts_with('x');
x.ends_with("x");
//~^ ERROR single-character string constant used as pattern
//~| HELP try using a char instead:
//~| SUGGESTION x.ends_with('x');
x.find("x");
//~^ ERROR single-character string constant used as pattern
//~| HELP try using a char instead:
//~| SUGGESTION x.find('x');
x.rfind("x");
//~^ ERROR single-character string constant used as pattern
//~| HELP try using a char instead:
//~| SUGGESTION x.rfind('x');
x.rsplit("x");
//~^ ERROR single-character string constant used as pattern
//~| HELP try using a char instead:
//~| SUGGESTION x.rsplit('x');
x.split_terminator("x");
//~^ ERROR single-character string constant used as pattern
//~| HELP try using a char instead:
//~| SUGGESTION x.split_terminator('x');
x.rsplit_terminator("x");
//~^ ERROR single-character string constant used as pattern
//~| HELP try using a char instead:
//~| SUGGESTION x.rsplit_terminator('x');
x.splitn(0, "x");
//~^ ERROR single-character string constant used as pattern
//~| HELP try using a char instead:
//~| SUGGESTION x.splitn(0, 'x');
x.rsplitn(0, "x");
//~^ ERROR single-character string constant used as pattern
//~| HELP try using a char instead:
//~| SUGGESTION x.rsplitn(0, 'x');
x.matches("x");
//~^ ERROR single-character string constant used as pattern
//~| HELP try using a char instead:
//~| SUGGESTION x.matches('x');
x.rmatches("x");
//~^ ERROR single-character string constant used as pattern
//~| HELP try using a char instead:
//~| SUGGESTION x.rmatches('x');
x.match_indices("x");
//~^ ERROR single-character string constant used as pattern
//~| HELP try using a char instead:
//~| SUGGESTION x.match_indices('x');
x.rmatch_indices("x");
//~^ ERROR single-character string constant used as pattern
//~| HELP try using a char instead:
//~| SUGGESTION x.rmatch_indices('x');
x.trim_left_matches("x");
//~^ ERROR single-character string constant used as pattern
//~| HELP try using a char instead:
//~| SUGGESTION x.trim_left_matches('x');
x.trim_right_matches("x");
//~^ ERROR single-character string constant used as pattern
//~| HELP try using a char instead:
//~| SUGGESTION x.trim_right_matches('x');
}