Bad suggestion of useless_let_if_seq when having side effects.
#4124
Labels
L-suggestion
Lint: Improving, adding or fixing lint suggestions
Comments
flip1995
added
the
L-suggestion
bors
added a commit
that referenced
this issue
May 15, 2020
Downgrade useless_let_if_seq to nursery
I feel that this lint has the wrong balance of incorrect suggestions for a default-enabled lint.
The immediate code I faced was something like:
```rust
fn main() {
let mut good = do1();
if !do2() {
good = false;
}
if good {
println!("good");
}
}
fn do1() -> bool { println!("1"); false }
fn do2() -> bool { println!("2"); false }
```
On this code Clippy calls it unidiomatic and suggests the following diff, which has different behavior in a way that I don't necessarily want.
```diff
- let mut good = do1();
- if !do2() {
- good = false;
- }
+ let good = if !do2() {
+ false
+ } else {
+ do1()
+ };
```
On exploring issues filed about this lint, I have found that other users have also struggled with inappropriate suggestions (#4124, #3043, #2918, #2176) and suggestions that make the code worse (#3769, #2749). Overall I believe that this lint is still at nursery quality for now and should not be enabled.
---
changelog: Remove useless_let_if_seq from default set of enabled lints
bors
added a commit
that referenced
this issue
May 15, 2020
Downgrade useless_let_if_seq to nursery
I feel that this lint has the wrong balance of incorrect suggestions for a default-enabled lint.
The immediate code I faced was something like:
```rust
fn main() {
let mut good = do1();
if !do2() {
good = false;
}
if good {
println!("good");
}
}
fn do1() -> bool { println!("1"); false }
fn do2() -> bool { println!("2"); false }
```
On this code Clippy calls it unidiomatic and suggests the following diff, which has different behavior in a way that I don't necessarily want.
```diff
- let mut good = do1();
- if !do2() {
- good = false;
- }
+ let good = if !do2() {
+ false
+ } else {
+ do1()
+ };
```
On exploring issues filed about this lint, I have found that other users have also struggled with inappropriate suggestions (#4124, #3043, #2918, #2176) and suggestions that make the code worse (#3769, #2749). Overall I believe that this lint is still at nursery quality for now and should not be enabled.
---
changelog: Remove useless_let_if_seq from default set of enabled lints
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The version of clippy is
0.0.212.Here's an example:
It suggest writing
let <mut> ret = if cond() { .. foo2() .. } else { foo1() };, which cause 3 function calls (may have side-effects) being reordered, andfoo1()not always being called.Well, I'm not sure how to write make it more idiomatic in this case...
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