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Don't flag if_not_else when else block is longer than then block #5654

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Don't flag if_not_else when else block is longer than then block #5654

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8 changes: 6 additions & 2 deletions clippy_lints/src/if_not_else.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -52,8 +52,12 @@ impl EarlyLintPass for IfNotElse {
if in_external_macro(cx.sess(), item.span) {
return;
}
if let ExprKind::If(ref cond, _, Some(ref els)) = item.kind {
if let ExprKind::Block(..) = els.kind {
if let ExprKind::If(ref cond, ref thn, Some(ref els)) = item.kind {
// Don't suggest rewriting if the result would be top-heavy.
if let ExprKind::Block(ref els_block, ..) = els.kind {
if thn.stmts.len() < els_block.stmts.len() {
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@flip1995 flip1995 Jun 11, 2020 •
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Because we already talked about cost-benefit:

The cost for this configuration option would be way higher, since this:

if !a {
    println!("xyz");
} else {
    let _ = if {
        // ...100 lines
    };
}

would still lint with this implementation. So we would need to implement a line counter. Or something that calculates complexity. But detecting complexity is a different story. Long story short: we can't do this (yet?, probably?, ...? #3793 (comment))

So what @sanmai-NL said, the cost for a working implementation for this would be too high for the benefit that it would give for a pedantic lint IMO.

return;
}
match cond.kind {
ExprKind::Unary(UnOp::Not, _) => {
span_lint_and_help(
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17 changes: 17 additions & 0 deletions tests/ui/if_not_else.rs
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Expand Up @@ -16,4 +16,21 @@ fn main() {
} else {
println!("Bunny");
}

// These won't get flagged because the body of the `else` block is
// longer than the body of the then-block.
if !bla() {
println!("Bugs");
} else {
println!("Bunny");
println!("Daffy");
println!("Duck");
}
if 4 != 5 {
println!("Bugs");
} else {
println!("Bunny");
println!("Daffy");
println!("Duck");
}
}