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This commit is contained in:
Josh Holmer 2018-08-31 18:26:04 -04:00
parent dfed9751bd
commit 061b2f3057
2 changed files with 41 additions and 35 deletions
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60
clippy_lints/src/loops.rs
View file

@ -14,6 +14,7 @@ use rustc::middle::mem_categorization::Categorization;
use rustc::middle::mem_categorization::cmt_;
use rustc::ty::{self, Ty};
use rustc::ty::subst::Subst;
use rustc_errors::Applicability;
use std::collections::{HashMap, HashSet};
use std::iter::{once, Iterator};
use syntax::ast;
@ -2267,6 +2268,8 @@ impl<'a, 'tcx> Visitor<'tcx> for VarCollectorVisitor<'a, 'tcx> {
}
}
const NEEDLESS_COLLECT_MSG: &str = "avoid using `collect()` when not needed";
fn check_needless_collect<'a, 'tcx>(expr: &'tcx Expr, cx: &LateContext<'a, 'tcx>) {
if let ExprKind::MethodCall(ref method, _, ref args) = expr.node {
if let ExprKind::MethodCall(ref chain_method, _, _) = args[0].node {
@ -2281,38 +2284,41 @@ fn check_needless_collect<'a, 'tcx>(expr: &'tcx Expr, cx: &LateContext<'a, 'tcx>
match_type(cx, ty, &paths::BTREEMAP) ||
match_type(cx, ty, &paths::HASHMAP) {
if method.ident.name == "len" {
span_lint_and_sugg(
cx,
NEEDLESS_COLLECT,
shorten_needless_collect_span(expr),
"you are collecting an iterator to check its length",
"consider replacing with",
".count()".to_string(),
);
let span = shorten_needless_collect_span(expr);
span_lint_and_then(cx, NEEDLESS_COLLECT, span, NEEDLESS_COLLECT_MSG, |db| {
db.span_suggestion_with_applicability(
span,
"replace with",
".count()".to_string(),
Applicability::MachineApplicable,
);
});
}
if method.ident.name == "is_empty" {
span_lint_and_sugg(
cx,
NEEDLESS_COLLECT,
shorten_needless_collect_span(expr),
"you are collecting an iterator to check if it is empty",
"consider replacing with",
".next().is_none()".to_string(),
);
let span = shorten_needless_collect_span(expr);
span_lint_and_then(cx, NEEDLESS_COLLECT, span, NEEDLESS_COLLECT_MSG, |db| {
db.span_suggestion_with_applicability(
span,
"replace with",
".next().is_none()".to_string(),
Applicability::MachineApplicable,
);
});
}
if method.ident.name == "contains" {
let contains_arg = snippet(cx, args[1].span, "??");
span_lint_and_sugg(
cx,
NEEDLESS_COLLECT,
shorten_needless_collect_span(expr),
"you are collecting an iterator to check if contains an element",
"consider replacing with",
format!(
".any(|&x| x == {})",
if contains_arg.starts_with('&') { &contains_arg[1..] } else { &contains_arg }
),
);
let span = shorten_needless_collect_span(expr);
span_lint_and_then(cx, NEEDLESS_COLLECT, span, NEEDLESS_COLLECT_MSG, |db| {
db.span_suggestion_with_applicability(
span,
"replace with",
format!(
".any(|&x| x == {})",
if contains_arg.starts_with('&') { &contains_arg[1..] } else { &contains_arg }
),
Applicability::MachineApplicable,
);
});
}
}
}

16
tests/ui/needless_collect.stderr
View file

@ -1,28 +1,28 @@
error: you are collecting an iterator to check its length
error: avoid using `collect()` when not needed
--> $DIR/needless_collect.rs:7:28
|
7 | let len = sample.iter().collect::<Vec<_>>().len();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider replacing with: `.count()`
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `.count()`
|
= note: `-D needless-collect` implied by `-D warnings`
error: you are collecting an iterator to check if it is empty
error: avoid using `collect()` when not needed
--> $DIR/needless_collect.rs:8:21
|
8 | if sample.iter().collect::<Vec<_>>().is_empty() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider replacing with: `.next().is_none()`
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `.next().is_none()`
error: you are collecting an iterator to check if contains an element
error: avoid using `collect()` when not needed
--> $DIR/needless_collect.rs:11:27
|
11 | sample.iter().cloned().collect::<Vec<_>>().contains(&1);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider replacing with: `.any(|&x| x == 1)`
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `.any(|&x| x == 1)`
error: you are collecting an iterator to check its length
error: avoid using `collect()` when not needed
--> $DIR/needless_collect.rs:12:34
|
12 | sample.iter().map(|x| (x, x)).collect::<HashMap<_, _>>().len();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider replacing with: `.count()`
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `.count()`
error: aborting due to 4 previous errors