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needless_collect: For BTreeMap and HashMap lint only is_empty

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- `len` might produce different results than `count`
- they don't have `contain` but `contains_key` method
This commit is contained in:
Mateusz Gacek 2021-05-05 12:08:24 -07:00
parent 182a1853c3
commit a21607d9b5
4 changed files with 63 additions and 33 deletions
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64
clippy_lints/src/loops/needless_collect.rs
View file

@ -10,7 +10,6 @@ use rustc_hir::intravisit::{walk_block, walk_expr, NestedVisitorMap, Visitor};
use rustc_hir::{Block, Expr, ExprKind, GenericArg, GenericArgs, HirId, Local, Pat, PatKind, QPath, StmtKind, Ty};
use rustc_lint::LateContext;
use rustc_middle::hir::map::Map;
use rustc_span::symbol::{sym, Ident};
use rustc_span::{MultiSpan, Span};
@ -28,32 +27,45 @@ fn check_needless_collect_direct_usage<'tcx>(expr: &'tcx Expr<'_>, cx: &LateCont
if let Some(generic_args) = chain_method.args;
if let Some(GenericArg::Type(ref ty)) = generic_args.args.get(0);
if let Some(ty) = cx.typeck_results().node_type_opt(ty.hir_id);
if is_type_diagnostic_item(cx, ty, sym::vec_type)
|| is_type_diagnostic_item(cx, ty, sym::vecdeque_type)
|| match_type(cx, ty, &paths::BTREEMAP)
|| is_type_diagnostic_item(cx, ty, sym::hashmap_type);
if let Some(sugg) = match &*method.ident.name.as_str() {
"len" => Some("count()".to_string()),
"is_empty" => Some("next().is_none()".to_string()),
"contains" => {
let contains_arg = snippet(cx, args[1].span, "??");
let (arg, pred) = contains_arg
.strip_prefix('&')
.map_or(("&x", &*contains_arg), |s| ("x", s));
Some(format!("any(|{}| x == {})", arg, pred))
}
_ => None,
};
then {
span_lint_and_sugg(
cx,
NEEDLESS_COLLECT,
method0_span.with_hi(expr.span.hi()),
NEEDLESS_COLLECT_MSG,
"replace with",
sugg,
Applicability::MachineApplicable,
);
let is_empty_sugg = Some("next().is_none()".to_string());
let method_name = &*method.ident.name.as_str();
let sugg = if is_type_diagnostic_item(cx, ty, sym::vec_type) ||
is_type_diagnostic_item(cx, ty, sym::vecdeque_type) {
match method_name {
"len" => Some("count()".to_string()),
"is_empty" => is_empty_sugg,
"contains" => {
let contains_arg = snippet(cx, args[1].span, "??");
let (arg, pred) = contains_arg
.strip_prefix('&')
.map_or(("&x", &*contains_arg), |s| ("x", s));
Some(format!("any(|{}| x == {})", arg, pred))
}
_ => None,
}
}
else if match_type(cx, ty, &paths::BTREEMAP) ||
is_type_diagnostic_item(cx, ty, sym::hashmap_type) {
match method_name {
"is_empty" => is_empty_sugg,
_ => None,
}
}
else {
None
};
if let Some(sugg) = sugg {
span_lint_and_sugg(
cx,
NEEDLESS_COLLECT,
method0_span.with_hi(expr.span.hi()),
NEEDLESS_COLLECT_MSG,
"replace with",
sugg,
Applicability::MachineApplicable,
);
}
}
}
}

10
tests/ui/needless_collect.fixed
View file

@ -2,7 +2,7 @@
#![allow(unused, clippy::suspicious_map, clippy::iter_count)]
use std::collections::{BTreeSet, HashMap, HashSet};
use std::collections::{BTreeMap, BTreeSet, HashMap, HashSet};
#[warn(clippy::needless_collect)]
#[allow(unused_variables, clippy::iter_cloned_collect, clippy::iter_next_slice)]
@ -13,7 +13,13 @@ fn main() {
// Empty
}
sample.iter().cloned().any(|x| x == 1);
sample.iter().map(|x| (x, x)).count();
// #7164 HashMap's and BTreeMap's `len` usage should not be linted
sample.iter().map(|x| (x, x)).collect::<HashMap<_, _>>().len();
sample.iter().map(|x| (x, x)).collect::<BTreeMap<_, _>>().len();
sample.iter().map(|x| (x, x)).next().is_none();
sample.iter().map(|x| (x, x)).next().is_none();
// Notice the `HashSet`--this should not be linted
sample.iter().collect::<HashSet<_>>().len();
// Neither should this

8
tests/ui/needless_collect.rs
View file

@ -2,7 +2,7 @@
#![allow(unused, clippy::suspicious_map, clippy::iter_count)]
use std::collections::{BTreeSet, HashMap, HashSet};
use std::collections::{BTreeMap, BTreeSet, HashMap, HashSet};
#[warn(clippy::needless_collect)]
#[allow(unused_variables, clippy::iter_cloned_collect, clippy::iter_next_slice)]
@ -13,7 +13,13 @@ fn main() {
// Empty
}
sample.iter().cloned().collect::<Vec<_>>().contains(&1);
// #7164 HashMap's and BTreeMap's `len` usage should not be linted
sample.iter().map(|x| (x, x)).collect::<HashMap<_, _>>().len();
sample.iter().map(|x| (x, x)).collect::<BTreeMap<_, _>>().len();
sample.iter().map(|x| (x, x)).collect::<HashMap<_, _>>().is_empty();
sample.iter().map(|x| (x, x)).collect::<BTreeMap<_, _>>().is_empty();
// Notice the `HashSet`--this should not be linted
sample.iter().collect::<HashSet<_>>().len();
// Neither should this

14
tests/ui/needless_collect.stderr
View file

@ -19,10 +19,16 @@ LL | sample.iter().cloned().collect::<Vec<_>>().contains(&1);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `any(|x| x == 1)`
error: avoid using `collect()` when not needed
--> $DIR/needless_collect.rs:16:35
--> $DIR/needless_collect.rs:20:35
|
LL | sample.iter().map(|x| (x, x)).collect::<HashMap<_, _>>().len();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `count()`
LL | sample.iter().map(|x| (x, x)).collect::<HashMap<_, _>>().is_empty();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `next().is_none()`
error: aborting due to 4 previous errors
error: avoid using `collect()` when not needed
--> $DIR/needless_collect.rs:21:35
|
LL | sample.iter().map(|x| (x, x)).collect::<BTreeMap<_, _>>().is_empty();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `next().is_none()`
error: aborting due to 5 previous errors