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Add lint for comparing floats in an array #4343

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Add lint for comparing floats in an array #4343

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11197c5
Add lint when comparing floats in an array
briankabiro Jul 31, 2019
1bf0d74
Merge branch 'master' into add-lint-for-float-in-array-comparison
briankabiro Sep 17, 2019
2471f90
Add tests for float in array comparison
briankabiro Sep 19, 2019
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7 changes: 7 additions & 0 deletions tests/ui/float_cmp.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -77,6 +77,13 @@ fn main() {

assert_eq!(a, b); // no errors

let a1: [f32; 1] = [0.0];
let a2: [f32; 1] = [1.1];
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@flip1995 flip1995 Sep 20, 2019 •
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Could you also add a test for the type [&f32; 1]?

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Thanks for the help.


assert_eq!(a1[0], a2[0]);
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If we want to do it right, this should not trigger the lint, since everything in a1 ist constant 0.0, so a comparison is ok here.

On a more general note, this enhancement needs more tests like the base case of comparing floats. (Comparing arrays of constant 0.0, constant {NEG_}INFINITY, ...)


assert_eq!(&a1[0], &a2[0]);

// no errors - comparing signums is ok
let x32 = 3.21f32;
1.23f32.signum() == x32.signum();
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28 changes: 27 additions & 1 deletion tests/ui/float_cmp.stderr
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Expand Up @@ -35,5 +35,31 @@ note: std::f32::EPSILON and std::f64::EPSILON are available.
LL | twice(x) != twice(ONE as f64);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 3 previous errors
error: strict comparison of f32 or f64
--> $DIR/float_cmp.rs:83:5
|
LL | assert_eq!(a1[0], a2[0]);
| ^^^^^^^^^^^^^^^^^^^^^^^^^
|
note: std::f32::EPSILON and std::f64::EPSILON are available.
--> $DIR/float_cmp.rs:83:5
|
LL | assert_eq!(a1[0], a2[0]);
| ^^^^^^^^^^^^^^^^^^^^^^^^^
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)

error: strict comparison of f32 or f64
--> $DIR/float_cmp.rs:85:5
|
LL | assert_eq!(&a1[0], &a2[0]);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
note: std::f32::EPSILON and std::f64::EPSILON are available.
--> $DIR/float_cmp.rs:85:5
|
LL | assert_eq!(&a1[0], &a2[0]);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)

error: aborting due to 5 previous errors