Fix missing parens in suboptimal_flops sugg

Fixes rust-lang#9391

Author: lukaslueg

clippy_lints/src/floating_point_arithmetic.rs

@@ -651,7 +651,7 @@ fn check_radians(cx: &LateContext<'_>, expr: &Expr<'_>) {
             if (F32(f32_consts::PI) == rvalue || F64(f64_consts::PI) == rvalue) &&
                (F32(180_f32) == lvalue || F64(180_f64) == lvalue)
             {
-                let mut proposal = format!("{}.to_degrees()", Sugg::hir(cx, mul_lhs, ".."));
+                let mut proposal = format!("{}.to_degrees()", Sugg::hir(cx, mul_lhs, "..").maybe_par());
                 if_chain! {
                     if let ExprKind::Lit(ref literal) = mul_lhs.kind;
                     if let ast::LitKind::Float(ref value, float_type) = literal.node;
@@ -677,7 +677,7 @@ fn check_radians(cx: &LateContext<'_>, expr: &Expr<'_>) {
                 (F32(180_f32) == rvalue || F64(180_f64) == rvalue) &&
                 (F32(f32_consts::PI) == lvalue || F64(f64_consts::PI) == lvalue)
             {
-                let mut proposal = format!("{}.to_radians()", Sugg::hir(cx, mul_lhs, ".."));
+                let mut proposal = format!("{}.to_radians()", Sugg::hir(cx, mul_lhs, "..").maybe_par());
                 if_chain! {
                     if let ExprKind::Lit(ref literal) = mul_lhs.kind;
                     if let ast::LitKind::Float(ref value, float_type) = literal.node;

tests/ui/floating_point_rad.fixed

@@ -8,6 +8,11 @@ pub const fn const_context() {
     let _ = x * 180f32 / std::f32::consts::PI;
 }
 
+pub fn issue9391(degrees: i64) {
+    let _ = (degrees as f64).to_radians();
+    let _ = (degrees as f64).to_degrees();
+}
+
 fn main() {
     let x = 3f32;
     let _ = x.to_degrees();

tests/ui/floating_point_rad.rs

@@ -8,6 +8,11 @@ pub const fn const_context() {
     let _ = x * 180f32 / std::f32::consts::PI;
 }
 
+pub fn issue9391(degrees: i64) {
+    let _ = degrees as f64 * std::f64::consts::PI / 180.0;
+    let _ = degrees as f64 * 180.0 / std::f64::consts::PI;
+}
+
 fn main() {
     let x = 3f32;
     let _ = x * 180f32 / std::f32::consts::PI;

tests/ui/floating_point_rad.stderr

@@ -1,40 +1,52 @@
+error: conversion to radians can be done more accurately
+  --> $DIR/floating_point_rad.rs:12:13
+   |
+LL |     let _ = degrees as f64 * std::f64::consts::PI / 180.0;
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `(degrees as f64).to_radians()`
+   |
+   = note: `-D clippy::suboptimal-flops` implied by `-D warnings`
+
 error: conversion to degrees can be done more accurately
   --> $DIR/floating_point_rad.rs:13:13
    |
+LL |     let _ = degrees as f64 * 180.0 / std::f64::consts::PI;
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `(degrees as f64).to_degrees()`
+
+error: conversion to degrees can be done more accurately
+  --> $DIR/floating_point_rad.rs:18:13
+   |
 LL |     let _ = x * 180f32 / std::f32::consts::PI;
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `x.to_degrees()`
-   |
-   = note: `-D clippy::suboptimal-flops` implied by `-D warnings`
 
 error: conversion to degrees can be done more accurately
-  --> $DIR/floating_point_rad.rs:14:13
+  --> $DIR/floating_point_rad.rs:19:13
    |
 LL |     let _ = 90. * 180f64 / std::f64::consts::PI;
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `90.0_f64.to_degrees()`
 
 error: conversion to degrees can be done more accurately
-  --> $DIR/floating_point_rad.rs:15:13
+  --> $DIR/floating_point_rad.rs:20:13
    |
 LL |     let _ = 90.5 * 180f64 / std::f64::consts::PI;
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `90.5_f64.to_degrees()`
 
 error: conversion to radians can be done more accurately
-  --> $DIR/floating_point_rad.rs:16:13
+  --> $DIR/floating_point_rad.rs:21:13
    |
 LL |     let _ = x * std::f32::consts::PI / 180f32;
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `x.to_radians()`
 
 error: conversion to radians can be done more accurately
-  --> $DIR/floating_point_rad.rs:17:13
+  --> $DIR/floating_point_rad.rs:22:13
    |
 LL |     let _ = 90. * std::f32::consts::PI / 180f32;
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `90.0_f64.to_radians()`
 
 error: conversion to radians can be done more accurately
-  --> $DIR/floating_point_rad.rs:18:13
+  --> $DIR/floating_point_rad.rs:23:13
    |
 LL |     let _ = 90.5 * std::f32::consts::PI / 180f32;
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `90.5_f64.to_radians()`
 
-error: aborting due to 6 previous errors
+error: aborting due to 8 previous errors