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clarify margin of error in wording of float comparison operator lint messages #6043

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merged 2 commits into from
Sep 15, 2020
Merged

clarify margin of error in wording of float comparison operator lint messages #6043

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4d73cca
clarify margin of error in wording of float comparison operator lint …
Sep 14, 2020
16b6ceb
update lint docs
Sep 15, 2020
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20 changes: 10 additions & 10 deletions clippy_lints/src/misc.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -99,11 +99,11 @@ declare_clippy_lint! {
/// if y != x {} // where both are floats
///
/// // Good
/// let error = f64::EPSILON; // Use an epsilon for comparison
/// let error_margin = f64::EPSILON; // Use an epsilon for comparison
/// // Or, if Rust <= 1.42, use `std::f64::EPSILON` constant instead.
/// // let error = std::f64::EPSILON;
/// if (y - 1.23f64).abs() < error { }
/// if (y - x).abs() > error { }
/// // let error_margin = std::f64::EPSILON;
/// if (y - 1.23f64).abs() < error_margin { }
/// if (y - x).abs() > error_margin { }
/// ```
pub FLOAT_CMP,
correctness,
Expand Down Expand Up @@ -242,10 +242,10 @@ declare_clippy_lint! {
/// if x == ONE { } // where both are floats
///
/// // Good
/// let error = f64::EPSILON; // Use an epsilon for comparison
/// let error_margin = f64::EPSILON; // Use an epsilon for comparison
/// // Or, if Rust <= 1.42, use `std::f64::EPSILON` constant instead.
/// // let error = std::f64::EPSILON;
/// if (x - ONE).abs() < error { }
/// // let error_margin = std::f64::EPSILON;
/// if (x - ONE).abs() < error_margin { }
/// ```
pub FLOAT_CMP_CONST,
restriction,
Expand Down Expand Up @@ -411,16 +411,16 @@ impl<'tcx> LateLintPass<'tcx> for MiscLints {
if !is_comparing_arrays {
diag.span_suggestion(
expr.span,
"consider comparing them within some error",
"consider comparing them within some margin of error",
format!(
"({}).abs() {} error",
"({}).abs() {} error_margin",
lhs - rhs,
if op == BinOpKind::Eq { '<' } else { '>' }
),
Applicability::HasPlaceholders, // snippet
);
}
diag.note("`f32::EPSILON` and `f64::EPSILON` are available for the `error`");
diag.note("`f32::EPSILON` and `f64::EPSILON` are available for the `error_margin`");
});
} else if op == BinOpKind::Rem && is_integer_const(cx, right, 1) {
span_lint(cx, MODULO_ONE, expr.span, "any number modulo 1 will be 0");
Expand Down
22 changes: 11 additions & 11 deletions tests/ui/float_cmp.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -2,50 +2,50 @@ error: strict comparison of `f32` or `f64`
--> $DIR/float_cmp.rs:65:5
|
LL | ONE as f64 != 2.0;
| ^^^^^^^^^^^^^^^^^ help: consider comparing them within some error: `(ONE as f64 - 2.0).abs() > error`
| ^^^^^^^^^^^^^^^^^ help: consider comparing them within some margin of error: `(ONE as f64 - 2.0).abs() > error_margin`
|
= note: `-D clippy::float-cmp` implied by `-D warnings`
= note: `f32::EPSILON` and `f64::EPSILON` are available for the `error`
= note: `f32::EPSILON` and `f64::EPSILON` are available for the `error_margin`

error: strict comparison of `f32` or `f64`
--> $DIR/float_cmp.rs:70:5
|
LL | x == 1.0;
| ^^^^^^^^ help: consider comparing them within some error: `(x - 1.0).abs() < error`
| ^^^^^^^^ help: consider comparing them within some margin of error: `(x - 1.0).abs() < error_margin`
|
= note: `f32::EPSILON` and `f64::EPSILON` are available for the `error`
= note: `f32::EPSILON` and `f64::EPSILON` are available for the `error_margin`

error: strict comparison of `f32` or `f64`
--> $DIR/float_cmp.rs:73:5
|
LL | twice(x) != twice(ONE as f64);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider comparing them within some error: `(twice(x) - twice(ONE as f64)).abs() > error`
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider comparing them within some margin of error: `(twice(x) - twice(ONE as f64)).abs() > error_margin`
|
= note: `f32::EPSILON` and `f64::EPSILON` are available for the `error`
= note: `f32::EPSILON` and `f64::EPSILON` are available for the `error_margin`

error: strict comparison of `f32` or `f64`
--> $DIR/float_cmp.rs:93:5
|
LL | NON_ZERO_ARRAY[i] == NON_ZERO_ARRAY[j];
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider comparing them within some error: `(NON_ZERO_ARRAY[i] - NON_ZERO_ARRAY[j]).abs() < error`
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider comparing them within some margin of error: `(NON_ZERO_ARRAY[i] - NON_ZERO_ARRAY[j]).abs() < error_margin`
|
= note: `f32::EPSILON` and `f64::EPSILON` are available for the `error`
= note: `f32::EPSILON` and `f64::EPSILON` are available for the `error_margin`

error: strict comparison of `f32` or `f64` arrays
--> $DIR/float_cmp.rs:98:5
|
LL | a1 == a2;
| ^^^^^^^^
|
= note: `f32::EPSILON` and `f64::EPSILON` are available for the `error`
= note: `f32::EPSILON` and `f64::EPSILON` are available for the `error_margin`

error: strict comparison of `f32` or `f64`
--> $DIR/float_cmp.rs:99:5
|
LL | a1[0] == a2[0];
| ^^^^^^^^^^^^^^ help: consider comparing them within some error: `(a1[0] - a2[0]).abs() < error`
| ^^^^^^^^^^^^^^ help: consider comparing them within some margin of error: `(a1[0] - a2[0]).abs() < error_margin`
|
= note: `f32::EPSILON` and `f64::EPSILON` are available for the `error`
= note: `f32::EPSILON` and `f64::EPSILON` are available for the `error_margin`

error: aborting due to 6 previous errors

30 changes: 15 additions & 15 deletions tests/ui/float_cmp_const.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -2,66 +2,66 @@ error: strict comparison of `f32` or `f64` constant
--> $DIR/float_cmp_const.rs:20:5
|
LL | 1f32 == ONE;
| ^^^^^^^^^^^ help: consider comparing them within some error: `(1f32 - ONE).abs() < error`
| ^^^^^^^^^^^ help: consider comparing them within some margin of error: `(1f32 - ONE).abs() < error_margin`
|
= note: `-D clippy::float-cmp-const` implied by `-D warnings`
= note: `f32::EPSILON` and `f64::EPSILON` are available for the `error`
= note: `f32::EPSILON` and `f64::EPSILON` are available for the `error_margin`

error: strict comparison of `f32` or `f64` constant
--> $DIR/float_cmp_const.rs:21:5
|
LL | TWO == ONE;
| ^^^^^^^^^^ help: consider comparing them within some error: `(TWO - ONE).abs() < error`
| ^^^^^^^^^^ help: consider comparing them within some margin of error: `(TWO - ONE).abs() < error_margin`
|
= note: `f32::EPSILON` and `f64::EPSILON` are available for the `error`
= note: `f32::EPSILON` and `f64::EPSILON` are available for the `error_margin`

error: strict comparison of `f32` or `f64` constant
--> $DIR/float_cmp_const.rs:22:5
|
LL | TWO != ONE;
| ^^^^^^^^^^ help: consider comparing them within some error: `(TWO - ONE).abs() > error`
| ^^^^^^^^^^ help: consider comparing them within some margin of error: `(TWO - ONE).abs() > error_margin`
|
= note: `f32::EPSILON` and `f64::EPSILON` are available for the `error`
= note: `f32::EPSILON` and `f64::EPSILON` are available for the `error_margin`

error: strict comparison of `f32` or `f64` constant
--> $DIR/float_cmp_const.rs:23:5
|
LL | ONE + ONE == TWO;
| ^^^^^^^^^^^^^^^^ help: consider comparing them within some error: `(ONE + ONE - TWO).abs() < error`
| ^^^^^^^^^^^^^^^^ help: consider comparing them within some margin of error: `(ONE + ONE - TWO).abs() < error_margin`
|
= note: `f32::EPSILON` and `f64::EPSILON` are available for the `error`
= note: `f32::EPSILON` and `f64::EPSILON` are available for the `error_margin`

error: strict comparison of `f32` or `f64` constant
--> $DIR/float_cmp_const.rs:25:5
|
LL | x as f32 == ONE;
| ^^^^^^^^^^^^^^^ help: consider comparing them within some error: `(x as f32 - ONE).abs() < error`
| ^^^^^^^^^^^^^^^ help: consider comparing them within some margin of error: `(x as f32 - ONE).abs() < error_margin`
|
= note: `f32::EPSILON` and `f64::EPSILON` are available for the `error`
= note: `f32::EPSILON` and `f64::EPSILON` are available for the `error_margin`

error: strict comparison of `f32` or `f64` constant
--> $DIR/float_cmp_const.rs:28:5
|
LL | v == ONE;
| ^^^^^^^^ help: consider comparing them within some error: `(v - ONE).abs() < error`
| ^^^^^^^^ help: consider comparing them within some margin of error: `(v - ONE).abs() < error_margin`
|
= note: `f32::EPSILON` and `f64::EPSILON` are available for the `error`
= note: `f32::EPSILON` and `f64::EPSILON` are available for the `error_margin`

error: strict comparison of `f32` or `f64` constant
--> $DIR/float_cmp_const.rs:29:5
|
LL | v != ONE;
| ^^^^^^^^ help: consider comparing them within some error: `(v - ONE).abs() > error`
| ^^^^^^^^ help: consider comparing them within some margin of error: `(v - ONE).abs() > error_margin`
|
= note: `f32::EPSILON` and `f64::EPSILON` are available for the `error`
= note: `f32::EPSILON` and `f64::EPSILON` are available for the `error_margin`

error: strict comparison of `f32` or `f64` constant arrays
--> $DIR/float_cmp_const.rs:61:5
|
LL | NON_ZERO_ARRAY == NON_ZERO_ARRAY2;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: `f32::EPSILON` and `f64::EPSILON` are available for the `error`
= note: `f32::EPSILON` and `f64::EPSILON` are available for the `error_margin`

error: aborting due to 8 previous errors