Auto merge of #4897 - krishna-veerareddy:issue-2040-accurate-float-functions, r=flip1995

Add lint to improve floating-point expressions

Looks for floating-point expressions that can be expressed using built-in methods to improve accuracy, performance and/or succinctness.

changelog: Add lint `floating_point_improvements`.

Fixes #4726
Partly addresses [#2040](#2040)

Currently linted expressions:

| Expression | Suggestion |
|---------------------------------|------------|
| x.log(2.0) | x.log2() |
| x.log(10.0) | x.log10() |
| x.log(std::f32::consts::E) | x.ln() |
| (1 + x).ln() | x.ln_1p() |
| (2.0).powf(x) | x.exp2() |
| (std::f32::consts::E).powf(x) | x.exp() |
| x.powf(1/2) | x.sqrt() |
| x.powf(1/3) | x.cbrt() |
| x.powf(y), where y is whole | x.powi(y) |
| x.exp() - 1 | x.exp_m1() |
|x * y + z|x.mul_add(y, z)|

Author: bors

CHANGELOG.md

@@ -1169,6 +1169,7 @@ Released 2018-09-13
 [`ifs_same_cond`]: https://rust-lang.github.io/rust-clippy/master/index.html#ifs_same_cond
 [`implicit_hasher`]: https://rust-lang.github.io/rust-clippy/master/index.html#implicit_hasher
 [`implicit_return`]: https://rust-lang.github.io/rust-clippy/master/index.html#implicit_return
+[`imprecise_flops`]: https://rust-lang.github.io/rust-clippy/master/index.html#imprecise_flops
 [`inconsistent_digit_grouping`]: https://rust-lang.github.io/rust-clippy/master/index.html#inconsistent_digit_grouping
 [`indexing_slicing`]: https://rust-lang.github.io/rust-clippy/master/index.html#indexing_slicing
 [`ineffective_bit_mask`]: https://rust-lang.github.io/rust-clippy/master/index.html#ineffective_bit_mask
@@ -1210,7 +1211,6 @@ Released 2018-09-13
 [`lossy_float_literal`]: https://rust-lang.github.io/rust-clippy/master/index.html#lossy_float_literal
 [`main_recursion`]: https://rust-lang.github.io/rust-clippy/master/index.html#main_recursion
 [`manual_memcpy`]: https://rust-lang.github.io/rust-clippy/master/index.html#manual_memcpy
-[`manual_mul_add`]: https://rust-lang.github.io/rust-clippy/master/index.html#manual_mul_add
 [`manual_saturating_arithmetic`]: https://rust-lang.github.io/rust-clippy/master/index.html#manual_saturating_arithmetic
 [`manual_swap`]: https://rust-lang.github.io/rust-clippy/master/index.html#manual_swap
 [`many_single_char_names`]: https://rust-lang.github.io/rust-clippy/master/index.html#many_single_char_names
@@ -1349,6 +1349,7 @@ Released 2018-09-13
 [`string_lit_as_bytes`]: https://rust-lang.github.io/rust-clippy/master/index.html#string_lit_as_bytes
 [`string_to_string`]: https://rust-lang.github.io/rust-clippy/master/index.html#string_to_string
 [`struct_excessive_bools`]: https://rust-lang.github.io/rust-clippy/master/index.html#struct_excessive_bools
+[`suboptimal_flops`]: https://rust-lang.github.io/rust-clippy/master/index.html#suboptimal_flops
 [`suspicious_arithmetic_impl`]: https://rust-lang.github.io/rust-clippy/master/index.html#suspicious_arithmetic_impl
 [`suspicious_assignment_formatting`]: https://rust-lang.github.io/rust-clippy/master/index.html#suspicious_assignment_formatting
 [`suspicious_else_formatting`]: https://rust-lang.github.io/rust-clippy/master/index.html#suspicious_else_formatting

README.md

@@ -5,7 +5,7 @@
 
 A collection of lints to catch common mistakes and improve your [Rust](https://github.com/rust-lang/rust) code.
 
-[There are 357 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
+[There are 358 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
 
 We have a bunch of lint categories to allow you to choose how much Clippy is supposed to ~~annoy~~ help you: