new lint: cmp_owned

This commit is contained in:
llogiq 2015-05-21 14:51:43 +02:00
parent 57a6b93ed0
commit 4292dc77a7
3 changed files with 68 additions and 1 deletions

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@ -44,6 +44,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
reg.register_lint_pass(box identity_op::IdentityOp as LintPassObject);
reg.register_lint_pass(box mut_mut::MutMut as LintPassObject);
reg.register_lint_pass(box len_zero::LenZero as LintPassObject);
reg.register_lint_pass(box misc::CmpOwned as LintPassObject);
reg.register_lint_group("clippy", vec![types::BOX_VEC, types::LINKEDLIST,
misc::SINGLE_MATCH, misc::STR_TO_STRING,
@ -54,7 +55,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
needless_bool::NEEDLESS_BOOL,
approx_const::APPROX_CONSTANT,
misc::CMP_NAN, misc::FLOAT_CMP,
misc::PRECEDENCE,
misc::PRECEDENCE, misc::CMP_OWNED,
eta_reduction::REDUNDANT_CLOSURE,
identity_op::IDENTITY_OP,
mut_mut::MUT_MUT,

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@ -211,3 +211,52 @@ fn is_arith_op(op : BinOp_) -> bool {
_ => false
}
}
declare_lint!(pub CMP_OWNED, Warn,
"Warn on creating an owned string just for comparison");
#[derive(Copy,Clone)]
pub struct CmpOwned;
impl LintPass for CmpOwned {
fn get_lints(&self) -> LintArray {
lint_array!(CMP_OWNED)
}
fn check_expr(&mut self, cx: &Context, expr: &Expr) {
if let ExprBinary(ref cmp, ref left, ref right) = expr.node {
if is_comparison_binop(cmp.node) {
check_to_owned(cx, left, right.span);
check_to_owned(cx, right, left.span)
}
}
}
}
fn check_to_owned(cx: &Context, expr: &Expr, other_span: Span) {
match &expr.node {
&ExprMethodCall(Spanned{node: ref ident, ..}, _, _) => {
let name = ident.as_str();
if name == "to_string" || name == "to_owned" {
cx.span_lint(CMP_OWNED, expr.span, &format!(
"this creates an owned instance just for comparison.
Consider using {}.as_slice() to compare without allocation",
cx.sess().codemap().span_to_snippet(other_span).unwrap_or(
"..".to_string())))
}
},
&ExprCall(ref path, _) => {
if let &ExprPath(None, ref path) = &path.node {
if path.segments.iter().zip(["String", "from_str"].iter()).all(
|(seg, name)| &seg.identifier.as_str() == name) {
cx.span_lint(CMP_OWNED, expr.span, &format!(
"this creates an owned instance just for comparison.
Consider using {}.as_slice() to compare without allocation",
cx.sess().codemap().span_to_snippet(other_span).unwrap_or(
"..".to_string())))
}
}
},
_ => ()
}
}

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@ -0,0 +1,17 @@
#![feature(plugin, collections)]
#![plugin(clippy)]
#[deny(cmp_owned)]
fn main() {
let x = "oh";
#[allow(str_to_string)]
fn with_to_string(x : &str) {
x != "foo".to_string(); //~ERROR this creates an owned instance
}
with_to_string(x);
x != "foo".to_owned(); //~ERROR this creates an owned instance
x != String::from_str("foo"); //~ERROR this creates an owned instance
}