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This commit is contained in:
Josh Holmer 2018-08-31 18:14:33 -04:00
parent fbc93c0166
commit dfed9751bd
3 changed files with 76 additions and 63 deletions
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104
clippy_lints/src/loops.rs
View file

@ -18,6 +18,7 @@ use std::collections::{HashMap, HashSet};
use std::iter::{once, Iterator};
use syntax::ast;
use syntax::source_map::Span;
use syntax_pos::BytePos;
use crate::utils::{sugg, sext};
use crate::utils::usage::mutated_variables;
use crate::consts::{constant, Constant};
@ -2269,63 +2270,62 @@ impl<'a, 'tcx> Visitor<'tcx> for VarCollectorVisitor<'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 chain_method, _, _) = args[0].node {
if chain_method.ident.name == "collect" && match_trait_method(cx, &args[0], &paths::ITERATOR) {
if method.ident.name == "len" {
span_lint_and_sugg(
cx,
NEEDLESS_COLLECT,
expr.span,
"you are collecting an iterator to check its length",
"consider replacing with",
generate_needless_collect_len_sugg(&args[0], cx),
);
}
if method.ident.name == "is_empty" {
span_lint_and_sugg(
cx,
NEEDLESS_COLLECT,
expr.span,
"you are collecting an iterator to check if it is empty",
"consider replacing with",
generate_needless_collect_is_empty_sugg(&args[0], cx),
);
}
if method.ident.name == "contains" {
span_lint_and_sugg(
cx,
NEEDLESS_COLLECT,
expr.span,
"you are collecting an iterator to check if contains an element",
"consider replacing with",
generate_needless_collect_contains_sugg(&args[0], &args[1], cx),
);
if chain_method.ident.name == "collect" &&
match_trait_method(cx, &args[0], &paths::ITERATOR) &&
chain_method.args.is_some() {
let generic_args = chain_method.args.as_ref().unwrap();
if let Some(GenericArg::Type(ref ty)) = generic_args.args.get(0) {
let ty = cx.tables.node_id_to_type(ty.hir_id);
if match_type(cx, ty, &paths::VEC) ||
match_type(cx, ty, &paths::VEC_DEQUE) ||
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(),
);
}
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(),
);
}
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 }
),
);
}
}
}
}
}
}
}
fn generate_needless_collect_len_sugg<'a, 'tcx>(collect_expr: &'tcx Expr, cx: &LateContext<'a, 'tcx>) -> String {
if let ExprKind::MethodCall(_, _, ref args) = collect_expr.node {
let iter = snippet(cx, args[0].span, "??");
return format!("{}.count()", iter);
fn shorten_needless_collect_span(expr: &Expr) -> Span {
if let ExprKind::MethodCall(_, _, ref args) = expr.node {
if let ExprKind::MethodCall(_, ref span, _) = args[0].node {
return expr.span.with_lo(span.lo() - BytePos(1));
}
}
unreachable!();
}
fn generate_needless_collect_is_empty_sugg<'a, 'tcx>(collect_expr: &'tcx Expr, cx: &LateContext<'a, 'tcx>) -> String {
if let ExprKind::MethodCall(_, _, ref args) = collect_expr.node {
let iter = snippet(cx, args[0].span, "??");
return format!("{}.any(|_| true)", iter);
}
unreachable!();
}
fn generate_needless_collect_contains_sugg<'a, 'tcx>(collect_expr: &'tcx Expr, contains_arg: &'tcx Expr, cx: &LateContext<'a, 'tcx>) -> String {
if let ExprKind::MethodCall(_, _, ref args) = collect_expr.node {
let iter = snippet(cx, args[0].span, "??");
let arg = snippet(cx, contains_arg.span, "??");
return format!("{}.any(|&x| x == {})", iter, if arg.starts_with('&') { &arg[1..] } else { &arg });
}
unreachable!();
unreachable!()
}

7
tests/ui/needless_collect.rs
View file

@ -1,3 +1,5 @@
use std::collections::{HashMap, HashSet, BTreeSet};
#[warn(clippy, needless_collect)]
#[allow(unused_variables, iter_cloned_collect)]
fn main() {
@ -7,4 +9,9 @@ fn main() {
// Empty
}
sample.iter().cloned().collect::<Vec<_>>().contains(&1);
sample.iter().map(|x| (x, x)).collect::<HashMap<_, _>>().len();
// Notice the `HashSet`--this should not be linted
sample.iter().collect::<HashSet<_>>().len();
// Neither should this
sample.iter().collect::<BTreeSet<_>>().len();
}

28
tests/ui/needless_collect.stderr
View file

@ -1,22 +1,28 @@
error: you are collecting an iterator to check its length
--> $DIR/needless_collect.rs:5:15
--> $DIR/needless_collect.rs:7:28
|
5 | let len = sample.iter().collect::<Vec<_>>().len();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider replacing with: `sample.iter().count()`
7 | let len = sample.iter().collect::<Vec<_>>().len();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider replacing with: `.count()`
|
= note: `-D needless-collect` implied by `-D warnings`
error: you are collecting an iterator to check if it is empty
--> $DIR/needless_collect.rs:6:8
--> $DIR/needless_collect.rs:8:21
|
6 | if sample.iter().collect::<Vec<_>>().is_empty() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider replacing with: `sample.iter().any(|_| true)`
8 | if sample.iter().collect::<Vec<_>>().is_empty() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider replacing with: `.next().is_none()`
error: you are collecting an iterator to check if contains an element
--> $DIR/needless_collect.rs:9:5
|
9 | sample.iter().cloned().collect::<Vec<_>>().contains(&1);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider replacing with: `sample.iter().cloned().any(|&x| x == 1)`
--> $DIR/needless_collect.rs:11:27
|
11 | sample.iter().cloned().collect::<Vec<_>>().contains(&1);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider replacing with: `.any(|&x| x == 1)`
error: aborting due to 3 previous errors
error: you are collecting an iterator to check its length
--> $DIR/needless_collect.rs:12:34
|
12 | sample.iter().map(|x| (x, x)).collect::<HashMap<_, _>>().len();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider replacing with: `.count()`
error: aborting due to 4 previous errors