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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::middle::mem_categorization::cmt_;
use rustc::ty::{self, Ty}; use rustc::ty::{self, Ty};
use rustc::ty::subst::Subst; use rustc::ty::subst::Subst;
use rustc_errors::Applicability;
use std::collections::{HashMap, HashSet}; use std::collections::{HashMap, HashSet};
use std::iter::{once, Iterator}; use std::iter::{once, Iterator};
use syntax::ast; 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>) { 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 method, _, ref args) = expr.node {
if let ExprKind::MethodCall(ref chain_method, _, _) = args[0].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::BTREEMAP) ||
match_type(cx, ty, &paths::HASHMAP) { match_type(cx, ty, &paths::HASHMAP) {
if method.ident.name == "len" { if method.ident.name == "len" {
span_lint_and_sugg( let span = shorten_needless_collect_span(expr);
cx, span_lint_and_then(cx, NEEDLESS_COLLECT, span, NEEDLESS_COLLECT_MSG, |db| {
NEEDLESS_COLLECT, db.span_suggestion_with_applicability(
shorten_needless_collect_span(expr), span,
"you are collecting an iterator to check its length", "replace with",
"consider replacing with", ".count()".to_string(),
".count()".to_string(), Applicability::MachineApplicable,
); );
});
} }
if method.ident.name == "is_empty" { if method.ident.name == "is_empty" {
span_lint_and_sugg( let span = shorten_needless_collect_span(expr);
cx, span_lint_and_then(cx, NEEDLESS_COLLECT, span, NEEDLESS_COLLECT_MSG, |db| {
NEEDLESS_COLLECT, db.span_suggestion_with_applicability(
shorten_needless_collect_span(expr), span,
"you are collecting an iterator to check if it is empty", "replace with",
"consider replacing with", ".next().is_none()".to_string(),
".next().is_none()".to_string(), Applicability::MachineApplicable,
); );
});
} }
if method.ident.name == "contains" { if method.ident.name == "contains" {
let contains_arg = snippet(cx, args[1].span, "??"); let contains_arg = snippet(cx, args[1].span, "??");
span_lint_and_sugg( let span = shorten_needless_collect_span(expr);
cx, span_lint_and_then(cx, NEEDLESS_COLLECT, span, NEEDLESS_COLLECT_MSG, |db| {
NEEDLESS_COLLECT, db.span_suggestion_with_applicability(
shorten_needless_collect_span(expr), span,
"you are collecting an iterator to check if contains an element", "replace with",
"consider replacing with", format!(
format!( ".any(|&x| x == {})",
".any(|&x| x == {})", if contains_arg.starts_with('&') { &contains_arg[1..] } else { &contains_arg }
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 --> $DIR/needless_collect.rs:7:28
| |
7 | let len = sample.iter().collect::<Vec<_>>().len(); 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` = 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 --> $DIR/needless_collect.rs:8:21
| |
8 | if sample.iter().collect::<Vec<_>>().is_empty() { 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 --> $DIR/needless_collect.rs:11:27
| |
11 | sample.iter().cloned().collect::<Vec<_>>().contains(&1); 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 --> $DIR/needless_collect.rs:12:34
| |
12 | sample.iter().map(|x| (x, x)).collect::<HashMap<_, _>>().len(); 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 error: aborting due to 4 previous errors