Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Implement "suspicious_map" lint #4394

Merged
merged 4 commits into from
Aug 18, 2019
Merged
Show file tree
Hide file tree
Changes from all commits
Commits
File filter

Filter by extension

Filter by extension

Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
1 change: 1 addition & 0 deletions CHANGELOG.md
Original file line number Diff line number Diff line change
Expand Up @@ -1152,6 +1152,7 @@ Released 2018-09-13
[`suspicious_arithmetic_impl`]: https://rust-lang.github.io/rust-clippy/master/index.html#suspicious_arithmetic_impl
[`suspicious_assignment_formatting`]: https://rust-lang.github.io/rust-clippy/master/index.html#suspicious_assignment_formatting
[`suspicious_else_formatting`]: https://rust-lang.github.io/rust-clippy/master/index.html#suspicious_else_formatting
[`suspicious_map`]: https://rust-lang.github.io/rust-clippy/master/index.html#suspicious_map
[`suspicious_op_assign_impl`]: https://rust-lang.github.io/rust-clippy/master/index.html#suspicious_op_assign_impl
[`temporary_assignment`]: https://rust-lang.github.io/rust-clippy/master/index.html#temporary_assignment
[`temporary_cstring_as_ptr`]: https://rust-lang.github.io/rust-clippy/master/index.html#temporary_cstring_as_ptr
Expand Down
2 changes: 1 addition & 1 deletion README.md
Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@

A collection of lints to catch common mistakes and improve your [Rust](https://github.com/rust-lang/rust) code.

[There are 309 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
[There are 310 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)

We have a bunch of lint categories to allow you to choose how much Clippy is supposed to ~~annoy~~ help you:

Expand Down
2 changes: 2 additions & 0 deletions clippy_lints/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -800,6 +800,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) {
methods::SHOULD_IMPLEMENT_TRAIT,
methods::SINGLE_CHAR_PATTERN,
methods::STRING_EXTEND_CHARS,
methods::SUSPICIOUS_MAP,
methods::TEMPORARY_CSTRING_AS_PTR,
methods::UNNECESSARY_FILTER_MAP,
methods::UNNECESSARY_FOLD,
Expand Down Expand Up @@ -1033,6 +1034,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) {
methods::FILTER_NEXT,
methods::FLAT_MAP_IDENTITY,
methods::SEARCH_IS_SOME,
methods::SUSPICIOUS_MAP,
methods::UNNECESSARY_FILTER_MAP,
methods::USELESS_ASREF,
misc::SHORT_CIRCUIT_STATEMENT,
Expand Down
32 changes: 31 additions & 1 deletion clippy_lints/src/methods/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,6 @@ use syntax::ast;
use syntax::source_map::Span;
use syntax::symbol::LocalInternedString;

use crate::utils::paths;
use crate::utils::sugg;
use crate::utils::usage::mutated_variables;
use crate::utils::{
Expand All @@ -28,6 +27,7 @@ use crate::utils::{
snippet, snippet_with_applicability, snippet_with_macro_callsite, span_lint, span_lint_and_sugg,
span_lint_and_then, span_note_and_lint, walk_ptrs_ty, walk_ptrs_ty_depth, SpanlessEq,
};
use crate::utils::{paths, span_help_and_lint};

declare_clippy_lint! {
/// **What it does:** Checks for `.unwrap()` calls on `Option`s.
Expand Down Expand Up @@ -889,6 +889,24 @@ declare_clippy_lint! {
"using `.into_iter()` on a reference"
}

declare_clippy_lint! {
/// **What it does:** Checks for calls to `map` followed by a `count`.
///
/// **Why is this bad?** It looks suspicious. Maybe `map` was confused with `filter`.
/// If the `map` call is intentional, this should be rewritten.
///
/// **Known problems:** None
///
/// **Example:**
///
/// ```rust
/// let _ = (0..3).map(|x| x + 2).count();
/// ```
pub SUSPICIOUS_MAP,
complexity,
"suspicious usage of map"
}

declare_lint_pass!(Methods => [
OPTION_UNWRAP_USED,
RESULT_UNWRAP_USED,
Expand Down Expand Up @@ -927,6 +945,7 @@ declare_lint_pass!(Methods => [
UNNECESSARY_FILTER_MAP,
INTO_ITER_ON_ARRAY,
INTO_ITER_ON_REF,
SUSPICIOUS_MAP,
]);

impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Methods {
Expand Down Expand Up @@ -972,6 +991,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Methods {
["as_mut"] => lint_asref(cx, expr, "as_mut", arg_lists[0]),
["fold", ..] => lint_unnecessary_fold(cx, expr, arg_lists[0]),
["filter_map", ..] => unnecessary_filter_map::lint(cx, expr, arg_lists[0]),
["count", "map"] => lint_suspicious_map(cx, expr),
_ => {},
}

Expand Down Expand Up @@ -2519,6 +2539,16 @@ fn lint_into_iter(cx: &LateContext<'_, '_>, expr: &hir::Expr, self_ref_ty: Ty<'_
}
}

fn lint_suspicious_map(cx: &LateContext<'_, '_>, expr: &hir::Expr) {
span_help_and_lint(
cx,
SUSPICIOUS_MAP,
expr.span,
"this call to `map()` won't have an effect on the call to `count()`",
"make sure you did not confuse `map` with `filter`",
);
}

/// Given a `Result<T, E>` type, return its error type (`E`).
fn get_error_type<'a>(cx: &LateContext<'_, '_>, ty: Ty<'a>) -> Option<Ty<'a>> {
if let ty::Adt(_, substs) = ty.sty {
Expand Down
9 changes: 8 additions & 1 deletion src/lintlist/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@ pub use lint::Lint;
pub use lint::LINT_LEVELS;

// begin lint list, do not remove this comment, it’s used in `update_lints`
pub const ALL_LINTS: [Lint; 309] = [
pub const ALL_LINTS: [Lint; 310] = [
Lint {
name: "absurd_extreme_comparisons",
group: "correctness",
Expand Down Expand Up @@ -1736,6 +1736,13 @@ pub const ALL_LINTS: [Lint; 309] = [
deprecation: None,
module: "formatting",
},
Lint {
name: "suspicious_map",
group: "complexity",
desc: "suspicious usage of map",
deprecation: None,
module: "methods",
},
Lint {
name: "suspicious_op_assign_impl",
group: "correctness",
Expand Down
5 changes: 5 additions & 0 deletions tests/ui/suspicious_map.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
#![warn(clippy::suspicious_map)]

fn main() {
let _ = (0..3).map(|x| x + 2).count();
}
11 changes: 11 additions & 0 deletions tests/ui/suspicious_map.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
error: this call to `map()` won't have an effect on the call to `count()`
--> $DIR/suspicious_map.rs:4:13
|
LL | let _ = (0..3).map(|x| x + 2).count();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: `-D clippy::suspicious-map` implied by `-D warnings`
= help: make sure you did not confuse `map` with `filter`

error: aborting due to previous error