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single_match_else - single expr/stmt else block corner case
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tnielens committed Jul 7, 2020
1 parent 57cdf2d commit c8c286c
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Showing 3 changed files with 106 additions and 9 deletions.
20 changes: 13 additions & 7 deletions clippy_lints/src/matches.rs
Original file line number Diff line number Diff line change
Expand Up @@ -530,16 +530,22 @@ fn check_single_match(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], exp
// the lint noisy in unnecessary situations
return;
}
let els = remove_blocks(&arms[1].body);
let els = if is_unit_expr(els) {
let els = arms[1].body;
let els = if is_unit_expr(remove_blocks(els)) {
None
} else if let ExprKind::Block(_, _) = els.kind {
// matches with blocks that contain statements are prettier as `if let + else`
Some(els)
} else if let ExprKind::Block(Block { stmts, expr: block_expr, .. }, _) = els.kind {
if stmts.len() == 1 && block_expr.is_none() || stmts.is_empty() && block_expr.is_some() {
// single statement/expr "else" block, don't lint
return;
} else {
// block with 2+ statements or 1 expr and 1+ statement
Some(els)
}
} else {
// allow match arms with just expressions
return;
// not a block, don't lint
return;
};

let ty = cx.tables().expr_ty(ex);
if ty.kind != ty::Bool || is_allowed(cx, MATCH_BOOL, ex.hir_id) {
check_single_match_single_pattern(cx, ex, arms, expr, els);
Expand Down
51 changes: 51 additions & 0 deletions tests/ui/single_match_else.rs
Original file line number Diff line number Diff line change
@@ -1,4 +1,6 @@
#![warn(clippy::single_match_else)]
#![allow(clippy::needless_return)]
#![allow(clippy::no_effect)]

enum ExprNode {
ExprAddrOf,
Expand Down Expand Up @@ -30,6 +32,55 @@ macro_rules! unwrap_addr {
};
}

#[rustfmt::skip]
fn main() {
unwrap_addr!(ExprNode::Unicorns);

//
// don't lint single exprs/statements
//

// don't lint here
match Some(1) {
Some(a) => println!("${:?}", a),
None => return,
}

// don't lint here
match Some(1) {
Some(a) => println!("${:?}", a),
None => {
return
},
}

// don't lint here
match Some(1) {
Some(a) => println!("${:?}", a),
None => {
return;
},
}

//
// lint multiple exprs/statements "else" blocks
//

// lint here
match Some(1) {
Some(a) => println!("${:?}", a),
None => {
println!("else block");
return
},
}

// lint here
match Some(1) {
Some(a) => println!("${:?}", a),
None => {
println!("else block");
return;
},
}
}
44 changes: 42 additions & 2 deletions tests/ui/single_match_else.stderr
Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
error: you seem to be trying to use match for destructuring a single pattern. Consider using `if let`
--> $DIR/single_match_else.rs:12:5
--> $DIR/single_match_else.rs:14:5
|
LL | / match ExprNode::Butterflies {
LL | | ExprNode::ExprAddrOf => Some(&NODE),
Expand All @@ -19,5 +19,45 @@ LL | None
LL | }
|

error: aborting due to previous error
error: you seem to be trying to use match for destructuring a single pattern. Consider using `if let`
--> $DIR/single_match_else.rs:70:5
|
LL | / match Some(1) {
LL | | Some(a) => println!("${:?}", a),
LL | | None => {
LL | | println!("else block");
LL | | return
LL | | },
LL | | }
| |_____^
|
help: try this
|
LL | if let Some(a) = Some(1) { println!("${:?}", a) } else {
LL | println!("else block");
LL | return
LL | }
|

error: you seem to be trying to use match for destructuring a single pattern. Consider using `if let`
--> $DIR/single_match_else.rs:79:5
|
LL | / match Some(1) {
LL | | Some(a) => println!("${:?}", a),
LL | | None => {
LL | | println!("else block");
LL | | return;
LL | | },
LL | | }
| |_____^
|
help: try this
|
LL | if let Some(a) = Some(1) { println!("${:?}", a) } else {
LL | println!("else block");
LL | return;
LL | }
|

error: aborting due to 3 previous errors

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