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Improve cmp_owned suggestions (fixes #386)

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This commit is contained in:
Manish Goregaokar 2015-10-13 04:16:05 +05:30
parent a04745e16c
commit 567d5a7293
2 changed files with 32 additions and 16 deletions
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42
src/misc.rs
View File

@ -165,37 +165,49 @@ impl LateLintPass for CmpOwned {
fn check_expr(&mut self, cx: &LateContext, 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)
check_to_owned(cx, left, right.span, true, cmp.span);
check_to_owned(cx, right, left.span, false, cmp.span)
}
}
}
}
fn check_to_owned(cx: &LateContext, expr: &Expr, other_span: Span) {
match expr.node {
ExprMethodCall(Spanned{node: ref name, ..}, _, ref args) => {
fn check_to_owned(cx: &LateContext, expr: &Expr, other_span: Span, left: bool, op: Span) {
let snip = match expr.node {
ExprMethodCall(Spanned{node: ref name, ..}, _, ref args) if args.len() == 1 => {
if name.as_str() == "to_string" ||
name.as_str() == "to_owned" && is_str_arg(cx, args) {
span_lint(cx, CMP_OWNED, expr.span, &format!(
"this creates an owned instance just for comparison. \
Consider using `{}.as_slice()` to compare without allocation",
snippet(cx, other_span, "..")))
snippet(cx, args[0].span, "..")
} else {
return
}
},
ExprCall(ref path, _) => {
ExprCall(ref path, ref v) if v.len() == 1 => {
if let &ExprPath(None, ref path) = &path.node {
if match_path(path, &["String", "from_str"]) ||
match_path(path, &["String", "from"]) {
span_lint(cx, CMP_OWNED, expr.span, &format!(
"this creates an owned instance just for comparison. \
Consider using `{}.as_slice()` to compare without allocation",
snippet(cx, other_span, "..")))
snippet(cx, v[0].span, "..")
} else {
return
}
} else {
return
}
},
_ => ()
_ => return
};
if left {
span_lint(cx, CMP_OWNED, expr.span, &format!(
"this creates an owned instance just for comparison. Consider using \
`{} {} {}` to compare without allocation", snip,
snippet(cx, op, "=="), snippet(cx, other_span, "..")));
} else {
span_lint(cx, CMP_OWNED, expr.span, &format!(
"this creates an owned instance just for comparison. Consider using \
`{} {} {}` to compare without allocation",
snippet(cx, other_span, ".."), snippet(cx, op, "=="), snip));
}
}
fn is_str_arg(cx: &LateContext, args: &[P<Expr>]) -> bool {

6
tests/compile-fail/cmp_owned.rs
View File

@ -7,7 +7,11 @@ fn main() {
#[allow(str_to_string)]
fn with_to_string(x : &str) {
x != "foo".to_string(); //~ERROR this creates an owned instance
x != "foo".to_string();
//~^ ERROR this creates an owned instance just for comparison. Consider using `x != "foo"` to compare without allocation
"foo".to_string() != x;
//~^ ERROR this creates an owned instance just for comparison. Consider using `"foo" != x` to compare without allocation
}
with_to_string(x);