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Auto merge of #4960 - ThibsG:patterns_with_wildcard_#4640, r=flip1995 

New lint: pats_with_wild_match_arm

Wildcard use with other pattern in same match arm.

The wildcard covers other(s) pattern(s) as it will match anyway.

changelog: add new lint when multiple patterns (including wildcard) are used in a match arm.

Fixes #4640.
This commit is contained in:
bors 2020-01-09 13:51:00 +00:00
parent 50403de386 0fa0df9efb
commit ac795a6f3a
10 changed files with 145 additions and 11 deletions
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1
CHANGELOG.md
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@ -1361,6 +1361,7 @@ Released 2018-09-13
[`while_let_on_iterator`]: https://rust-lang.github.io/rust-clippy/master/index.html#while_let_on_iterator
[`wildcard_dependencies`]: https://rust-lang.github.io/rust-clippy/master/index.html#wildcard_dependencies
[`wildcard_enum_match_arm`]: https://rust-lang.github.io/rust-clippy/master/index.html#wildcard_enum_match_arm
[`wildcard_in_or_patterns`]: https://rust-lang.github.io/rust-clippy/master/index.html#wildcard_in_or_patterns
[`write_literal`]: https://rust-lang.github.io/rust-clippy/master/index.html#write_literal
[`write_with_newline`]: https://rust-lang.github.io/rust-clippy/master/index.html#write_with_newline
[`writeln_empty_string`]: https://rust-lang.github.io/rust-clippy/master/index.html#writeln_empty_string

2
README.md
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@ -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 345 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
[There are 346 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:

3
clippy_lints/src/lib.rs
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@ -600,6 +600,7 @@ pub fn register_plugins(store: &mut lint::LintStore, sess: &Session, conf: &Conf
&matches::SINGLE_MATCH,
&matches::SINGLE_MATCH_ELSE,
&matches::WILDCARD_ENUM_MATCH_ARM,
&matches::WILDCARD_IN_OR_PATTERNS,
&mem_discriminant::MEM_DISCRIMINANT_NON_ENUM,
&mem_forget::MEM_FORGET,
&mem_replace::MEM_REPLACE_OPTION_WITH_NONE,
@ -1188,6 +1189,7 @@ pub fn register_plugins(store: &mut lint::LintStore, sess: &Session, conf: &Conf
LintId::of(&matches::MATCH_REF_PATS),
LintId::of(&matches::MATCH_WILD_ERR_ARM),
LintId::of(&matches::SINGLE_MATCH),
LintId::of(&matches::WILDCARD_IN_OR_PATTERNS),
LintId::of(&mem_discriminant::MEM_DISCRIMINANT_NON_ENUM),
LintId::of(&mem_replace::MEM_REPLACE_OPTION_WITH_NONE),
LintId::of(&mem_replace::MEM_REPLACE_WITH_DEFAULT),
@ -1462,6 +1464,7 @@ pub fn register_plugins(store: &mut lint::LintStore, sess: &Session, conf: &Conf
LintId::of(&map_unit_fn::OPTION_MAP_UNIT_FN),
LintId::of(&map_unit_fn::RESULT_MAP_UNIT_FN),
LintId::of(&matches::MATCH_AS_REF),
LintId::of(&matches::WILDCARD_IN_OR_PATTERNS),
LintId::of(&methods::CHARS_NEXT_CMP),
LintId::of(&methods::CLONE_ON_COPY),
LintId::of(&methods::FILTER_NEXT),

44
clippy_lints/src/matches.rs
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@ -3,7 +3,8 @@ use crate::utils::paths;
use crate::utils::sugg::Sugg;
use crate::utils::{
expr_block, is_allowed, is_expn_of, match_qpath, match_type, multispan_sugg, remove_blocks, snippet,
snippet_with_applicability, span_lint_and_sugg, span_lint_and_then, span_note_and_lint, walk_ptrs_ty,
snippet_with_applicability, span_help_and_lint, span_lint_and_sugg, span_lint_and_then, span_note_and_lint,
walk_ptrs_ty,
};
use if_chain::if_chain;
use rustc::declare_lint_pass;
@ -223,6 +224,26 @@ declare_clippy_lint! {
"a wildcard enum match arm using `_`"
}
declare_clippy_lint! {
/// **What it does:** Checks for wildcard pattern used with others patterns in same match arm.
///
/// **Why is this bad?** Wildcard pattern already covers any other pattern as it will match anyway.
/// It makes the code less readable, especially to spot wildcard pattern use in match arm.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// match "foo" {
/// "a" => {},
/// "bar" | _ => {},
/// }
/// ```
pub WILDCARD_IN_OR_PATTERNS,
complexity,
"a wildcard pattern used with others patterns in same match arm"
}
declare_lint_pass!(Matches => [
SINGLE_MATCH,
MATCH_REF_PATS,
@ -231,7 +252,8 @@ declare_lint_pass!(Matches => [
MATCH_OVERLAPPING_ARM,
MATCH_WILD_ERR_ARM,
MATCH_AS_REF,
WILDCARD_ENUM_MATCH_ARM
WILDCARD_ENUM_MATCH_ARM,
WILDCARD_IN_OR_PATTERNS
]);
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Matches {
@ -246,6 +268,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Matches {
check_wild_err_arm(cx, ex, arms);
check_wild_enum_match(cx, ex, arms);
check_match_as_ref(cx, ex, arms, expr);
check_wild_in_or_pats(cx, arms);
}
if let ExprKind::Match(ref ex, ref arms, _) = expr.kind {
check_match_ref_pats(cx, ex, arms, expr);
@ -664,6 +687,23 @@ fn check_match_as_ref(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>],
}
}
fn check_wild_in_or_pats(cx: &LateContext<'_, '_>, arms: &[Arm<'_>]) {
for arm in arms {
if let PatKind::Or(ref fields) = arm.pat.kind {
// look for multiple fields in this arm that contains at least one Wild pattern
if fields.len() > 1 && fields.iter().any(is_wild) {
span_help_and_lint(
cx,
WILDCARD_IN_OR_PATTERNS,
arm.pat.span,
"wildcard pattern covers any other pattern as it will match anyway.",
"Consider handling `_` separately.",
);
}
}
}
}
/// Gets all arms that are unbounded `PatRange`s.
fn all_ranges<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, arms: &'tcx [Arm<'_>]) -> Vec<SpannedRange<Constant>> {
arms.iter()

9
src/lintlist/mod.rs
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@ -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; 345] = [
pub const ALL_LINTS: [Lint; 346] = [
Lint {
name: "absurd_extreme_comparisons",
group: "correctness",
@ -2345,6 +2345,13 @@ pub const ALL_LINTS: [Lint; 345] = [
deprecation: None,
module: "matches",
},
Lint {
name: "wildcard_in_or_patterns",
group: "complexity",
desc: "a wildcard pattern used with others patterns in same match arm",
deprecation: None,
module: "matches",
},
Lint {
name: "write_literal",
group: "style",

36
tests/ui/wild_in_or_pats.rs Normal file
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@ -0,0 +1,36 @@
#![warn(clippy::wildcard_in_or_patterns)]
fn main() {
match "foo" {
"a" => {
dbg!("matched a");
},
"bar" | _ => {
dbg!("matched (bar or) wild");
},
};
match "foo" {
"a" => {
dbg!("matched a");
},
"bar" | "bar2" | _ => {
dbg!("matched (bar or bar2 or) wild");
},
};
match "foo" {
"a" => {
dbg!("matched a");
},
_ | "bar" | _ => {
dbg!("matched (bar or) wild");
},
};
match "foo" {
"a" => {
dbg!("matched a");
},
_ | "bar" => {
dbg!("matched (bar or) wild");
},
};
}

35
tests/ui/wild_in_or_pats.stderr Normal file
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@ -0,0 +1,35 @@
error: wildcard pattern covers any other pattern as it will match anyway.
--> $DIR/wild_in_or_pats.rs:8:9
|
LL | "bar" | _ => {
| ^^^^^^^^^
|
= note: `-D clippy::wildcard-in-or-patterns` implied by `-D warnings`
= help: Consider handling `_` separately.
error: wildcard pattern covers any other pattern as it will match anyway.
--> $DIR/wild_in_or_pats.rs:16:9
|
LL | "bar" | "bar2" | _ => {
| ^^^^^^^^^^^^^^^^^^
|
= help: Consider handling `_` separately.
error: wildcard pattern covers any other pattern as it will match anyway.
--> $DIR/wild_in_or_pats.rs:24:9
|
LL | _ | "bar" | _ => {
| ^^^^^^^^^^^^^
|
= help: Consider handling `_` separately.
error: wildcard pattern covers any other pattern as it will match anyway.
--> $DIR/wild_in_or_pats.rs:32:9
|
LL | _ | "bar" => {
| ^^^^^^^^^
|
= help: Consider handling `_` separately.
error: aborting due to 4 previous errors

8
tests/ui/wildcard_enum_match_arm.fixed
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@ -1,7 +1,13 @@
// run-rustfix
#![deny(clippy::wildcard_enum_match_arm)]
#![allow(unreachable_code, unused_variables, dead_code, clippy::single_match)]
#![allow(
unreachable_code,
unused_variables,
dead_code,
clippy::single_match,
clippy::wildcard_in_or_patterns
)]
use std::io::ErrorKind;

8
tests/ui/wildcard_enum_match_arm.rs
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@ -1,7 +1,13 @@
// run-rustfix
#![deny(clippy::wildcard_enum_match_arm)]
#![allow(unreachable_code, unused_variables, dead_code, clippy::single_match)]
#![allow(
unreachable_code,
unused_variables,
dead_code,
clippy::single_match,
clippy::wildcard_in_or_patterns
)]
use std::io::ErrorKind;

10
tests/ui/wildcard_enum_match_arm.stderr
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@ -1,5 +1,5 @@
error: wildcard match will miss any future added variants
--> $DIR/wildcard_enum_match_arm.rs:31:9
--> $DIR/wildcard_enum_match_arm.rs:37:9
|
LL | _ => eprintln!("Not red"),
| ^ help: try this: `Color::Green | Color::Blue | Color::Rgb(..) | Color::Cyan`
@ -11,25 +11,25 @@ LL | #![deny(clippy::wildcard_enum_match_arm)]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: wildcard match will miss any future added variants
--> $DIR/wildcard_enum_match_arm.rs:35:9
--> $DIR/wildcard_enum_match_arm.rs:41:9
|
LL | _not_red => eprintln!("Not red"),
| ^^^^^^^^ help: try this: `_not_red @ Color::Green | _not_red @ Color::Blue | _not_red @ Color::Rgb(..) | _not_red @ Color::Cyan`
error: wildcard match will miss any future added variants
--> $DIR/wildcard_enum_match_arm.rs:39:9
--> $DIR/wildcard_enum_match_arm.rs:45:9
|
LL | not_red => format!("{:?}", not_red),
| ^^^^^^^ help: try this: `not_red @ Color::Green | not_red @ Color::Blue | not_red @ Color::Rgb(..) | not_red @ Color::Cyan`
error: wildcard match will miss any future added variants
--> $DIR/wildcard_enum_match_arm.rs:55:9
--> $DIR/wildcard_enum_match_arm.rs:61:9
|
LL | _ => "No red",
| ^ help: try this: `Color::Red | Color::Green | Color::Blue | Color::Rgb(..) | Color::Cyan`
error: match on non-exhaustive enum doesn't explicitly match all known variants
--> $DIR/wildcard_enum_match_arm.rs:72:9
--> $DIR/wildcard_enum_match_arm.rs:78:9
|
LL | _ => {},
| ^ help: try this: `std::io::ErrorKind::PermissionDenied | std::io::ErrorKind::ConnectionRefused | std::io::ErrorKind::ConnectionReset | std::io::ErrorKind::ConnectionAborted | std::io::ErrorKind::NotConnected | std::io::ErrorKind::AddrInUse | std::io::ErrorKind::AddrNotAvailable | std::io::ErrorKind::BrokenPipe | std::io::ErrorKind::AlreadyExists | std::io::ErrorKind::WouldBlock | std::io::ErrorKind::InvalidInput | std::io::ErrorKind::InvalidData | std::io::ErrorKind::TimedOut | std::io::ErrorKind::WriteZero | std::io::ErrorKind::Interrupted | std::io::ErrorKind::Other | std::io::ErrorKind::UnexpectedEof | _`