Auto merge of #5664 - ThibsG:GiveCorrectedCode, r=flip1995

Give corrected code

This PR adds corrected code for doc examples.

I did this in several commits to facilitate review.
Don't hesitate to tell me if I forgot some.
Also, sometimes I felt it was not necessary to give corrected code, but I maybe wrong.

fixes: #4829

changelog: Improve documentation examples across multiple lints.

Author: bors

clippy_lints/src/assign_ops.rs

@@ -24,7 +24,11 @@ declare_clippy_lint! {
     /// let mut a = 5;
     /// let b = 0;
     /// // ...
+    /// // Bad
     /// a = a + b;
+    ///
+    /// // Good
+    /// a += b;
     /// ```
     pub ASSIGN_OP_PATTERN,
     style,

clippy_lints/src/double_parens.rs

@@ -13,10 +13,24 @@ declare_clippy_lint! {
     ///
     /// **Example:**
     /// ```rust
+    /// // Bad
+    /// fn simple_double_parens() -> i32 {
+    ///     ((0))
+    /// }
+    ///
+    /// // Good
+    /// fn simple_no_parens() -> i32 {
+    ///     0
+    /// }
+    ///
+    /// // or
+    ///
     /// # fn foo(bar: usize) {}
-    /// ((0));
+    /// // Bad
     /// foo((0));
-    /// ((1, 2));
+    ///
+    /// // Good
+    /// foo(0);
     /// ```
     pub DOUBLE_PARENS,
     complexity,

clippy_lints/src/drop_bounds.rs

@@ -27,6 +27,10 @@ declare_clippy_lint! {
     /// ```rust
     /// fn foo<T: Drop>() {}
     /// ```
+    /// Could be written as:
+    /// ```rust
+    /// fn foo<T>() {}
+    /// ```
     pub DROP_BOUNDS,
     correctness,
     "Bounds of the form `T: Drop` are useless"

clippy_lints/src/duration_subsec.rs

@@ -22,8 +22,14 @@ declare_clippy_lint! {
     /// ```rust
     /// # use std::time::Duration;
     /// let dur = Duration::new(5, 0);
+    ///
+    /// // Bad
     /// let _micros = dur.subsec_nanos() / 1_000;
     /// let _millis = dur.subsec_nanos() / 1_000_000;
+    ///
+    /// // Good
+    /// let _micros = dur.subsec_micros();
+    /// let _millis = dur.subsec_millis();
     /// ```
     pub DURATION_SUBSEC,
     complexity,

clippy_lints/src/enum_variants.rs

@@ -25,31 +25,47 @@ declare_clippy_lint! {
     ///     BattenbergCake,
     /// }
     /// ```
+    /// Could be written as:
+    /// ```rust
+    /// enum Cake {
+    ///     BlackForest,
+    ///     Hummingbird,
+    ///     Battenberg,
+    /// }
+    /// ```
     pub ENUM_VARIANT_NAMES,
     style,
     "enums where all variants share a prefix/postfix"
 }
 
 declare_clippy_lint! {
-    /// **What it does:** Detects enumeration variants that are prefixed or suffixed
-    /// by the same characters.
+    /// **What it does:** Detects public enumeration variants that are
+    /// prefixed or suffixed by the same characters.
     ///
-    /// **Why is this bad?** Enumeration variant names should specify their variant,
+    /// **Why is this bad?** Public enumeration variant names should specify their variant,
     /// not repeat the enumeration name.
     ///
     /// **Known problems:** None.
     ///
     /// **Example:**
     /// ```rust
-    /// enum Cake {
+    /// pub enum Cake {
     ///     BlackForestCake,
     ///     HummingbirdCake,
     ///     BattenbergCake,
     /// }
     /// ```
+    /// Could be written as:
+    /// ```rust
+    /// pub enum Cake {
+    ///     BlackForest,
+    ///     Hummingbird,
+    ///     Battenberg,
+    /// }
+    /// ```
     pub PUB_ENUM_VARIANT_NAMES,
     pedantic,
-    "enums where all variants share a prefix/postfix"
+    "public enums where all variants share a prefix/postfix"
 }
 
 declare_clippy_lint! {
@@ -66,6 +82,12 @@ declare_clippy_lint! {
     ///     struct BlackForestCake;
     /// }
     /// ```
+    /// Could be written as:
+    /// ```rust
+    /// mod cake {
+    ///     struct BlackForest;
+    /// }
+    /// ```
     pub MODULE_NAME_REPETITIONS,
     pedantic,
     "type names prefixed/postfixed with their containing module's name"

clippy_lints/src/eq_op.rs

@@ -39,7 +39,11 @@ declare_clippy_lint! {
     ///
     /// **Example:**
     /// ```ignore
+    /// // Bad
     /// &x == y
+    ///
+    /// // Good
+    /// x == *y
     /// ```
     pub OP_REF,
     style,

clippy_lints/src/escape.rs

@@ -28,9 +28,16 @@ declare_clippy_lint! {
     /// **Example:**
     /// ```rust
     /// # fn foo(bar: usize) {}
+    ///
+    /// // Bad
     /// let x = Box::new(1);
     /// foo(*x);
     /// println!("{}", *x);
+    ///
+    /// // Good
+    /// let x = 1;
+    /// foo(x);
+    /// println!("{}", x);
     /// ```
     pub BOXED_LOCAL,
     perf,

clippy_lints/src/eta_reduction.rs

@@ -26,7 +26,11 @@ declare_clippy_lint! {
     ///
     /// **Example:**
     /// ```rust,ignore
+    /// // Bad
     /// xs.map(|x| foo(x))
+    ///
+    /// // Good
+    /// xs.map(foo)
     /// ```
     /// where `foo(_)` is a plain function that takes the exact argument type of
     /// `x`.

clippy_lints/src/eval_order_dependence.rs

@@ -21,11 +21,20 @@ declare_clippy_lint! {
     /// **Example:**
     /// ```rust
     /// let mut x = 0;
+    ///
+    /// // Bad
     /// let a = {
     ///     x = 1;
     ///     1
     /// } + x;
     /// // Unclear whether a is 1 or 2.
+    ///
+    /// // Good
+    /// let tmp = {
+    ///     x = 1;
+    ///     1
+    /// };
+    /// let a = tmp + x;
     /// ```
     pub EVAL_ORDER_DEPENDENCE,
     complexity,

clippy_lints/src/fallible_impl_from.rs

@@ -20,12 +20,31 @@ declare_clippy_lint! {
     /// **Example:**
     /// ```rust
     /// struct Foo(i32);
+    ///
+    /// // Bad
     /// impl From<String> for Foo {
     ///     fn from(s: String) -> Self {
     ///         Foo(s.parse().unwrap())
     ///     }
     /// }
     /// ```
+    ///
+    /// ```rust
+    /// // Good
+    /// struct Foo(i32);
+    ///
+    /// use std::convert::TryFrom;
+    /// impl TryFrom<String> for Foo {
+    ///     type Error = ();
+    ///     fn try_from(s: String) -> Result<Self, Self::Error> {
+    ///         if let Ok(parsed) = s.parse() {
+    ///             Ok(Foo(parsed))
+    ///         } else {
+    ///             Err(())
+    ///         }
+    ///     }
+    /// }
+    /// ```
     pub FALLIBLE_IMPL_FROM,
     nursery,
     "Warn on impls of `From<..>` that contain `panic!()` or `unwrap()`"
@@ -120,7 +139,7 @@ fn lint_impl_body<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, impl_span: Span, impl_it
                         move |diag| {
                             diag.help(
                                 "`From` is intended for infallible conversions only. \
-                                 Use `TryFrom` if there's a possibility for the conversion to fail.");
+                                Use `TryFrom` if there's a possibility for the conversion to fail.");
                             diag.span_note(fpu.result, "potential failure(s)");
                         });
                 }