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Improve message for match_single_arms

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This commit is contained in:
Jason Newcomb 2022-01-21 21:30:34 -05:00
parent 4f8f4b4c82
commit 08a7157a37
4 changed files with 261 additions and 246 deletions
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80
clippy_lints/src/matches/match_same_arms.rs
View file

@ -4,6 +4,7 @@ use clippy_utils::{path_to_local, search_same, SpanlessEq, SpanlessHash};
use core::iter;
use rustc_arena::DroplessArena;
use rustc_ast::ast::LitKind;
use rustc_errors::Applicability;
use rustc_hir::def_id::DefId;
use rustc_hir::{Arm, Expr, ExprKind, HirId, HirIdMap, HirIdSet, Pat, PatKind, RangeEnd};
use rustc_lint::LateContext;
@ -13,6 +14,7 @@ use std::collections::hash_map::Entry;
use super::MATCH_SAME_ARMS;
#[allow(clippy::too_many_lines)]
pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, arms: &'tcx [Arm<'_>]) {
let hash = |&(_, arm): &(usize, &Arm<'_>)| -> u64 {
let mut h = SpanlessHash::new(cx);
@ -96,42 +98,52 @@ pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, arms: &'tcx [Arm<'_>]) {
};
let indexed_arms: Vec<(usize, &Arm<'_>)> = arms.iter().enumerate().collect();
for (&(_, i), &(_, j)) in search_same(&indexed_arms, hash, eq) {
span_lint_and_then(
cx,
MATCH_SAME_ARMS,
j.body.span,
"this `match` has identical arm bodies",
|diag| {
diag.span_note(i.body.span, "same as this");
for (&(i, arm1), &(j, arm2)) in search_same(&indexed_arms, hash, eq) {
if matches!(arm2.pat.kind, PatKind::Wild) {
span_lint_and_then(
cx,
MATCH_SAME_ARMS,
arm1.span,
"this match arm has an identical body to the `_` wildcard arm",
|diag| {
diag.span_suggestion(
arm1.span,
"try removing the arm",
String::new(),
Applicability::MaybeIncorrect,
)
.help("or try changing either arm body")
.span_note(arm2.span, "`_` wildcard arm here");
},
);
} else {
let back_block = backwards_blocking_idxs[j];
let (keep_arm, move_arm) = if back_block < i || (back_block == 0 && forwards_blocking_idxs[i] <= j) {
(arm1, arm2)
} else {
(arm2, arm1)
};
// Note: this does not use `span_suggestion` on purpose:
// there is no clean way
// to remove the other arm. Building a span and suggest to replace it to ""
// makes an even more confusing error message. Also in order not to make up a
// span for the whole pattern, the suggestion is only shown when there is only
// one pattern. The user should know about `|` if they are already using it…
span_lint_and_then(
cx,
MATCH_SAME_ARMS,
keep_arm.span,
"this match arm has an identical body to another arm",
|diag| {
let move_pat_snip = snippet(cx, move_arm.pat.span, "<pat2>");
let keep_pat_snip = snippet(cx, keep_arm.pat.span, "<pat1>");
let lhs = snippet(cx, i.pat.span, "<pat1>");
let rhs = snippet(cx, j.pat.span, "<pat2>");
if let PatKind::Wild = j.pat.kind {
// if the last arm is _, then i could be integrated into _
// note that i.pat cannot be _, because that would mean that we're
// hiding all the subsequent arms, and rust won't compile
diag.span_note(
i.body.span,
&format!(
"`{}` has the same arm body as the `_` wildcard, consider removing it",
lhs
),
);
} else {
diag.span_help(i.pat.span, &format!("consider refactoring into `{} | {}`", lhs, rhs,))
.help("...or consider changing the match arm bodies");
}
},
);
diag.span_suggestion(
keep_arm.pat.span,
"try merging the arm patterns",
format!("{} | {}", keep_pat_snip, move_pat_snip),
Applicability::MaybeIncorrect,
)
.help("or try changing either arm body")
.span_note(move_arm.span, "other arm here");
},
);
}
}
}

165
tests/ui/match_same_arms.stderr
View file

@ -1,128 +1,121 @@
error: this `match` has identical arm bodies
--> $DIR/match_same_arms.rs:13:14
error: this match arm has an identical body to the `_` wildcard arm
--> $DIR/match_same_arms.rs:11:9
|
LL | _ => 0, //~ ERROR match arms have same body
| ^
LL | Abc::A => 0,
| ^^^^^^^^^^^ help: try removing the arm
|
= note: `-D clippy::match-same-arms` implied by `-D warnings`
note: same as this
--> $DIR/match_same_arms.rs:11:19
= help: or try changing either arm body
note: `_` wildcard arm here
--> $DIR/match_same_arms.rs:13:9
|
LL | Abc::A => 0,
| ^
note: `Abc::A` has the same arm body as the `_` wildcard, consider removing it
--> $DIR/match_same_arms.rs:11:19
|
LL | Abc::A => 0,
| ^
LL | _ => 0, //~ ERROR match arms have same body
| ^^^^^^
error: this `match` has identical arm bodies
--> $DIR/match_same_arms.rs:18:20
|
LL | (.., 3) => 42, //~ ERROR match arms have same body
| ^^
|
note: same as this
--> $DIR/match_same_arms.rs:17:23
|
LL | (1, .., 3) => 42,
| ^^
help: consider refactoring into `(1, .., 3) | (.., 3)`
error: this match arm has an identical body to another arm
--> $DIR/match_same_arms.rs:17:9
|
LL | (1, .., 3) => 42,
| ^^^^^^^^^^
= help: ...or consider changing the match arm bodies
| ----------^^^^^^
| |
| help: try merging the arm patterns: `(1, .., 3) | (.., 3)`
|
= help: or try changing either arm body
note: other arm here
--> $DIR/match_same_arms.rs:18:9
|
LL | (.., 3) => 42, //~ ERROR match arms have same body
| ^^^^^^^^^^^^^
error: this `match` has identical arm bodies
--> $DIR/match_same_arms.rs:24:15
error: this match arm has an identical body to another arm
--> $DIR/match_same_arms.rs:24:9
|
LL | 51 => 1, //~ ERROR match arms have same body
| ^
| --^^^^^
| |
| help: try merging the arm patterns: `51 | 42`
|
note: same as this
--> $DIR/match_same_arms.rs:23:15
|
LL | 42 => 1,
| ^
help: consider refactoring into `42 | 51`
= help: or try changing either arm body
note: other arm here
--> $DIR/match_same_arms.rs:23:9
|
LL | 42 => 1,
| ^^
= help: ...or consider changing the match arm bodies
| ^^^^^^^
error: this `match` has identical arm bodies
--> $DIR/match_same_arms.rs:26:15
|
LL | 52 => 2, //~ ERROR match arms have same body
| ^
|
note: same as this
--> $DIR/match_same_arms.rs:25:15
|
LL | 41 => 2,
| ^
help: consider refactoring into `41 | 52`
error: this match arm has an identical body to another arm
--> $DIR/match_same_arms.rs:25:9
|
LL | 41 => 2,
| ^^
= help: ...or consider changing the match arm bodies
| --^^^^^
| |
| help: try merging the arm patterns: `41 | 52`
|
= help: or try changing either arm body
note: other arm here
--> $DIR/match_same_arms.rs:26:9
|
LL | 52 => 2, //~ ERROR match arms have same body
| ^^^^^^^
error: this `match` has identical arm bodies
--> $DIR/match_same_arms.rs:32:14
error: this match arm has an identical body to another arm
--> $DIR/match_same_arms.rs:32:9
|
LL | 2 => 2, //~ ERROR 2nd matched arms have same body
| ^
| -^^^^^
| |
| help: try merging the arm patterns: `2 | 1`
|
note: same as this
--> $DIR/match_same_arms.rs:31:14
|
LL | 1 => 2,
| ^
help: consider refactoring into `1 | 2`
= help: or try changing either arm body
note: other arm here
--> $DIR/match_same_arms.rs:31:9
|
LL | 1 => 2,
| ^
= help: ...or consider changing the match arm bodies
| ^^^^^^
error: this `match` has identical arm bodies
--> $DIR/match_same_arms.rs:33:14
error: this match arm has an identical body to another arm
--> $DIR/match_same_arms.rs:33:9
|
LL | 3 => 2, //~ ERROR 3rd matched arms have same body
| ^
| -^^^^^
| |
| help: try merging the arm patterns: `3 | 1`
|
note: same as this
--> $DIR/match_same_arms.rs:31:14
|
LL | 1 => 2,
| ^
help: consider refactoring into `1 | 3`
= help: or try changing either arm body
note: other arm here
--> $DIR/match_same_arms.rs:31:9
|
LL | 1 => 2,
| ^
= help: ...or consider changing the match arm bodies
| ^^^^^^
error: this `match` has identical arm bodies
--> $DIR/match_same_arms.rs:50:55
error: this match arm has an identical body to another arm
--> $DIR/match_same_arms.rs:32:9
|
LL | 2 => 2, //~ ERROR 2nd matched arms have same body
| -^^^^^
| |
| help: try merging the arm patterns: `2 | 3`
|
= help: or try changing either arm body
note: other arm here
--> $DIR/match_same_arms.rs:33:9
|
LL | 3 => 2, //~ ERROR 3rd matched arms have same body
| ^^^^^^
error: this match arm has an identical body to another arm
--> $DIR/match_same_arms.rs:50:17
|
LL | CommandInfo::External { name, .. } => name.to_string(),
| ^^^^^^^^^^^^^^^^
| ----------------------------------^^^^^^^^^^^^^^^^^^^^
| |
| help: try merging the arm patterns: `CommandInfo::External { name, .. } | CommandInfo::BuiltIn { name, .. }`
|
note: same as this
--> $DIR/match_same_arms.rs:49:54
|
LL | CommandInfo::BuiltIn { name, .. } => name.to_string(),
| ^^^^^^^^^^^^^^^^
help: consider refactoring into `CommandInfo::BuiltIn { name, .. } | CommandInfo::External { name, .. }`
= help: or try changing either arm body
note: other arm here
--> $DIR/match_same_arms.rs:49:17
|
LL | CommandInfo::BuiltIn { name, .. } => name.to_string(),
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
= help: ...or consider changing the match arm bodies
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: aborting due to 7 previous errors
error: aborting due to 8 previous errors

17
tests/ui/match_same_arms2.rs
View file

@ -181,10 +181,27 @@ fn main() {
Z(u32),
}
// Don't lint. `Foo::X(0)` and `Foo::Z(_)` overlap with the arm in between.
let _ = match Foo::X(0) {
Foo::X(0) => 1,
Foo::X(_) | Foo::Y(_) | Foo::Z(0) => 2,
Foo::Z(_) => 1,
_ => 0,
};
// Suggest moving `Foo::Z(_)` up.
let _ = match Foo::X(0) {
Foo::X(0) => 1,
Foo::X(_) | Foo::Y(_) => 2,
Foo::Z(_) => 1,
_ => 0,
};
// Suggest moving `Foo::X(0)` down.
let _ = match Foo::X(0) {
Foo::X(0) => 1,
Foo::Y(_) | Foo::Z(0) => 2,
Foo::Z(_) => 1,
_ => 0,
};
}

245
tests/ui/match_same_arms2.stderr
View file

@ -1,175 +1,138 @@
error: this `match` has identical arm bodies
--> $DIR/match_same_arms2.rs:20:14
error: this match arm has an identical body to the `_` wildcard arm
--> $DIR/match_same_arms2.rs:11:9
|
LL | _ => {
| ______________^
LL | / 42 => {
LL | | foo();
LL | | let mut a = 42 + [23].len() as i32;
LL | | if true {
... |
LL | | a
LL | | },
| |_________^ help: try removing the arm
|
= note: `-D clippy::match-same-arms` implied by `-D warnings`
= help: or try changing either arm body
note: `_` wildcard arm here
--> $DIR/match_same_arms2.rs:20:9
|
LL | / _ => {
LL | | //~ ERROR match arms have same body
LL | | foo();
LL | | let mut a = 42 + [23].len() as i32;
... |
LL | | a
LL | | },
| |_________^
|
= note: `-D clippy::match-same-arms` implied by `-D warnings`
note: same as this
--> $DIR/match_same_arms2.rs:11:15
|
LL | 42 => {
| _______________^
LL | | foo();
LL | | let mut a = 42 + [23].len() as i32;
LL | | if true {
... |
LL | | a
LL | | },
| |_________^
note: `42` has the same arm body as the `_` wildcard, consider removing it
--> $DIR/match_same_arms2.rs:11:15
|
LL | 42 => {
| _______________^
LL | | foo();
LL | | let mut a = 42 + [23].len() as i32;
LL | | if true {
... |
LL | | a
LL | | },
| |_________^
error: this `match` has identical arm bodies
--> $DIR/match_same_arms2.rs:34:15
error: this match arm has an identical body to another arm
--> $DIR/match_same_arms2.rs:34:9
|
LL | 51 => foo(), //~ ERROR match arms have same body
| ^^^^^
| --^^^^^^^^^
| |
| help: try merging the arm patterns: `51 | 42`
|
note: same as this
--> $DIR/match_same_arms2.rs:33:15
|
LL | 42 => foo(),
| ^^^^^
help: consider refactoring into `42 | 51`
= help: or try changing either arm body
note: other arm here
--> $DIR/match_same_arms2.rs:33:9
|
LL | 42 => foo(),
| ^^
= help: ...or consider changing the match arm bodies
| ^^^^^^^^^^^
error: this `match` has identical arm bodies
--> $DIR/match_same_arms2.rs:40:17
|
LL | None => 24, //~ ERROR match arms have same body
| ^^
|
note: same as this
--> $DIR/match_same_arms2.rs:39:20
|
LL | Some(_) => 24,
| ^^
help: consider refactoring into `Some(_) | None`
error: this match arm has an identical body to another arm
--> $DIR/match_same_arms2.rs:39:9
|
LL | Some(_) => 24,
| ^^^^^^^
= help: ...or consider changing the match arm bodies
| -------^^^^^^
| |
| help: try merging the arm patterns: `Some(_) | None`
|
= help: or try changing either arm body
note: other arm here
--> $DIR/match_same_arms2.rs:40:9
|
LL | None => 24, //~ ERROR match arms have same body
| ^^^^^^^^^^
error: this `match` has identical arm bodies
--> $DIR/match_same_arms2.rs:62:28
|
LL | (None, Some(a)) => bar(a), //~ ERROR match arms have same body
| ^^^^^^
|
note: same as this
--> $DIR/match_same_arms2.rs:61:28
|
LL | (Some(a), None) => bar(a),
| ^^^^^^
help: consider refactoring into `(Some(a), None) | (None, Some(a))`
error: this match arm has an identical body to another arm
--> $DIR/match_same_arms2.rs:61:9
|
LL | (Some(a), None) => bar(a),
| ^^^^^^^^^^^^^^^
= help: ...or consider changing the match arm bodies
| ---------------^^^^^^^^^^
| |
| help: try merging the arm patterns: `(Some(a), None) | (None, Some(a))`
|
= help: or try changing either arm body
note: other arm here
--> $DIR/match_same_arms2.rs:62:9
|
LL | (None, Some(a)) => bar(a), //~ ERROR match arms have same body
| ^^^^^^^^^^^^^^^^^^^^^^^^^
error: this `match` has identical arm bodies
--> $DIR/match_same_arms2.rs:68:26
|
LL | (.., Some(a)) => bar(a), //~ ERROR match arms have same body
| ^^^^^^
|
note: same as this
--> $DIR/match_same_arms2.rs:67:26
|
LL | (Some(a), ..) => bar(a),
| ^^^^^^
help: consider refactoring into `(Some(a), ..) | (.., Some(a))`
error: this match arm has an identical body to another arm
--> $DIR/match_same_arms2.rs:67:9
|
LL | (Some(a), ..) => bar(a),
| ^^^^^^^^^^^^^
= help: ...or consider changing the match arm bodies
| -------------^^^^^^^^^^
| |
| help: try merging the arm patterns: `(Some(a), ..) | (.., Some(a))`
|
= help: or try changing either arm body
note: other arm here
--> $DIR/match_same_arms2.rs:68:9
|
LL | (.., Some(a)) => bar(a), //~ ERROR match arms have same body
| ^^^^^^^^^^^^^^^^^^^^^^^
error: this `match` has identical arm bodies
--> $DIR/match_same_arms2.rs:102:29
|
LL | (Ok(_), Some(x)) => println!("ok {}", x),
| ^^^^^^^^^^^^^^^^^^^^
|
note: same as this
--> $DIR/match_same_arms2.rs:101:29
|
LL | (Ok(x), Some(_)) => println!("ok {}", x),
| ^^^^^^^^^^^^^^^^^^^^
help: consider refactoring into `(Ok(x), Some(_)) | (Ok(_), Some(x))`
error: this match arm has an identical body to another arm
--> $DIR/match_same_arms2.rs:101:9
|
LL | (Ok(x), Some(_)) => println!("ok {}", x),
| ^^^^^^^^^^^^^^^^
= help: ...or consider changing the match arm bodies
= note: this error originates in the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
| ----------------^^^^^^^^^^^^^^^^^^^^^^^^
| |
| help: try merging the arm patterns: `(Ok(x), Some(_)) | (Ok(_), Some(x))`
|
= help: or try changing either arm body
note: other arm here
--> $DIR/match_same_arms2.rs:102:9
|
LL | (Ok(_), Some(x)) => println!("ok {}", x),
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: this `match` has identical arm bodies
--> $DIR/match_same_arms2.rs:117:18
error: this match arm has an identical body to another arm
--> $DIR/match_same_arms2.rs:117:9
|
LL | Ok(_) => println!("ok"),
| ^^^^^^^^^^^^^^
| -----^^^^^^^^^^^^^^^^^^
| |
| help: try merging the arm patterns: `Ok(_) | Ok(3)`
|
note: same as this
--> $DIR/match_same_arms2.rs:116:18
|
LL | Ok(3) => println!("ok"),
| ^^^^^^^^^^^^^^
help: consider refactoring into `Ok(3) | Ok(_)`
= help: or try changing either arm body
note: other arm here
--> $DIR/match_same_arms2.rs:116:9
|
LL | Ok(3) => println!("ok"),
| ^^^^^
= help: ...or consider changing the match arm bodies
= note: this error originates in the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
| ^^^^^^^^^^^^^^^^^^^^^^^
error: this `match` has identical arm bodies
--> $DIR/match_same_arms2.rs:144:14
error: this match arm has an identical body to another arm
--> $DIR/match_same_arms2.rs:144:9
|
LL | 1 => {
| ______________^
| ^ help: try merging the arm patterns: `1 | 0`
| _________|
| |
LL | | empty!(0);
LL | | },
| |_________^
|
note: same as this
--> $DIR/match_same_arms2.rs:141:14
|
LL | 0 => {
| ______________^
LL | | empty!(0);
LL | | },
| |_________^
help: consider refactoring into `0 | 1`
= help: or try changing either arm body
note: other arm here
--> $DIR/match_same_arms2.rs:141:9
|
LL | 0 => {
| ^
= help: ...or consider changing the match arm bodies
LL | / 0 => {
LL | | empty!(0);
LL | | },
| |_________^
error: match expression looks like `matches!` macro
--> $DIR/match_same_arms2.rs:162:16
@ -184,5 +147,35 @@ LL | | };
|
= note: `-D clippy::match-like-matches-macro` implied by `-D warnings`
error: aborting due to 9 previous errors
error: this match arm has an identical body to another arm
--> $DIR/match_same_arms2.rs:194:9
|
LL | Foo::X(0) => 1,
| ---------^^^^^
| |
| help: try merging the arm patterns: `Foo::X(0) | Foo::Z(_)`
|
= help: or try changing either arm body
note: other arm here
--> $DIR/match_same_arms2.rs:196:9
|
LL | Foo::Z(_) => 1,
| ^^^^^^^^^^^^^^
error: this match arm has an identical body to another arm
--> $DIR/match_same_arms2.rs:204:9
|
LL | Foo::Z(_) => 1,
| ---------^^^^^
| |
| help: try merging the arm patterns: `Foo::Z(_) | Foo::X(0)`
|
= help: or try changing either arm body
note: other arm here
--> $DIR/match_same_arms2.rs:202:9
|
LL | Foo::X(0) => 1,
| ^^^^^^^^^^^^^^
error: aborting due to 11 previous errors