Doctests: Enable running doc tests for perf lints

This should be possible to merge independently of #4325

cc #4319

10 files changed, 65 insertions, 32 deletions

diff --git a/clippy_lints/src/bytecount.rs b/clippy_lints/src/bytecount.rs
index 98485838261..ab9cf951261 100644
--- a/clippy_lints/src/bytecount.rs
+++ b/clippy_lints/src/bytecount.rs
@@ -24,7 +24,8 @@ declare_clippy_lint! {
     /// **Example:**
     ///
     /// ```rust
-    /// &my_data.filter(|&x| x == 0u8).count() // use bytecount::count instead
+    /// # let vec = vec![1_u8];
+    /// &vec.iter().filter(|x| **x == 0u8).count(); // use bytecount::count instead
     /// ```
     pub NAIVE_BYTECOUNT,
     perf,
diff --git a/clippy_lints/src/entry.rs b/clippy_lints/src/entry.rs
index 83f78b2d72d..e6b09f89b35 100644
--- a/clippy_lints/src/entry.rs
+++ b/clippy_lints/src/entry.rs
@@ -16,21 +16,32 @@ declare_clippy_lint! {
     ///
     /// **Known problems:** Some false negatives, eg.:
     /// ```rust
-    /// let k = &key;
-    /// if !m.contains_key(k) {
-    ///     m.insert(k.clone(), v);
+    /// # use std::collections::HashMap;
+    /// # let mut map = HashMap::new();
+    /// # let v = 1;
+    /// # let k = 1;
+    /// if !map.contains_key(&k) {
+    ///     map.insert(k.clone(), v);
     /// }
     /// ```
     ///
     /// **Example:**
     /// ```rust
-    /// if !m.contains_key(&k) {
-    ///     m.insert(k, v)
+    /// # use std::collections::HashMap;
+    /// # let mut map = HashMap::new();
+    /// # let k = 1;
+    /// # let v = 1;
+    /// if !map.contains_key(&k) {
+    ///     map.insert(k, v);
     /// }
     /// ```
-    /// can be rewritten as:
+    /// can both be rewritten as:
     /// ```rust
-    /// m.entry(k).or_insert(v);
+    /// # use std::collections::HashMap;
+    /// # let mut map = HashMap::new();
+    /// # let k = 1;
+    /// # let v = 1;
+    /// map.entry(k).or_insert(v);
     /// ```
     pub MAP_ENTRY,
     perf,
diff --git a/clippy_lints/src/escape.rs b/clippy_lints/src/escape.rs
index f276014f43a..c37efbd6e49 100644
--- a/clippy_lints/src/escape.rs
+++ b/clippy_lints/src/escape.rs
@@ -28,11 +28,10 @@ declare_clippy_lint! {
     ///
     /// **Example:**
     /// ```rust
-    /// fn main() {
-    ///     let x = Box::new(1);
-    ///     foo(*x);
-    ///     println!("{}", *x);
-    /// }
+    /// # fn foo(bar: usize) {}
+    /// let x = Box::new(1);
+    /// foo(*x);
+    /// println!("{}", *x);
     /// ```
     pub BOXED_LOCAL,
     perf,
diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs
index 1e9e17f599c..8a29e187e4e 100644
--- a/clippy_lints/src/lib.rs
+++ b/clippy_lints/src/lib.rs
@@ -105,7 +105,7 @@ macro_rules! declare_clippy_lint {
     };
     { $(#[$attr:meta])* pub $name:tt, perf, $description:tt } => {
         declare_tool_lint! {
-            pub clippy::$name, Warn, $description, report_in_external_macro: true
+            $(#[$attr])* pub clippy::$name, Warn, $description, report_in_external_macro: true
         }
     };
     { $(#[$attr:meta])* pub $name:tt, pedantic, $description:tt } => {
@@ -120,7 +120,7 @@ macro_rules! declare_clippy_lint {
     };
     { $(#[$attr:meta])* pub $name:tt, cargo, $description:tt } => {
         declare_tool_lint! {
-            pub clippy::$name, Allow, $description, report_in_external_macro: true
+            $(#[$attr])* pub clippy::$name, Allow, $description, report_in_external_macro: true
         }
     };
     { $(#[$attr:meta])* pub $name:tt, nursery, $description:tt } => {
diff --git a/clippy_lints/src/loops.rs b/clippy_lints/src/loops.rs
index 02074c79b41..940da9b3fad 100644
--- a/clippy_lints/src/loops.rs
+++ b/clippy_lints/src/loops.rs
@@ -41,7 +41,9 @@ declare_clippy_lint! {
     /// **Known problems:** None.
     ///
     /// **Example:**
-    /// ```ignore
+    /// ```rust
+    /// # let src = vec![1];
+    /// # let mut dst = vec![0; 65];
     /// for i in 0..src.len() {
     ///     dst[i + 64] = src[i];
     /// }
@@ -264,8 +266,9 @@ declare_clippy_lint! {
     /// None
     ///
     /// **Example:**
-    /// ```ignore
-    /// let len = iterator.collect::<Vec<_>>().len();
+    /// ```rust
+    /// # let iterator = vec![1].into_iter();
+    /// let len = iterator.clone().collect::<Vec<_>>().len();
     /// // should be
     /// let len = iterator.count();
     /// ```
diff --git a/clippy_lints/src/methods/mod.rs b/clippy_lints/src/methods/mod.rs
index 02dfb3e32aa..8ae08f584b9 100644
--- a/clippy_lints/src/methods/mod.rs
+++ b/clippy_lints/src/methods/mod.rs
@@ -383,15 +383,18 @@ declare_clippy_lint! {
     ///
     /// **Example:**
     /// ```rust
-    /// foo.unwrap_or(String::new())
+    /// # let foo = Some(String::new());
+    /// foo.unwrap_or(String::new());
     /// ```
     /// this can instead be written:
     /// ```rust
-    /// foo.unwrap_or_else(String::new)
+    /// # let foo = Some(String::new());
+    /// foo.unwrap_or_else(String::new);
     /// ```
     /// or
     /// ```rust
-    /// foo.unwrap_or_default()
+    /// # let foo = Some(String::new());
+    /// foo.unwrap_or_default();
     /// ```
     pub OR_FUN_CALL,
     perf,
@@ -409,15 +412,24 @@ declare_clippy_lint! {
     ///
     /// **Example:**
     /// ```rust
-    /// foo.expect(&format!("Err {}: {}", err_code, err_msg))
+    /// # let foo = Some(String::new());
+    /// # let err_code = "418";
+    /// # let err_msg = "I'm a teapot";
+    /// foo.expect(&format!("Err {}: {}", err_code, err_msg));
     /// ```
     /// or
     /// ```rust
-    /// foo.expect(format!("Err {}: {}", err_code, err_msg).as_str())
+    /// # let foo = Some(String::new());
+    /// # let err_code = "418";
+    /// # let err_msg = "I'm a teapot";
+    /// foo.expect(format!("Err {}: {}", err_code, err_msg).as_str());
     /// ```
     /// this can instead be written:
     /// ```rust
-    /// foo.unwrap_or_else(|_| panic!("Err {}: {}", err_code, err_msg))
+    /// # let foo = Some(String::new());
+    /// # let err_code = "418";
+    /// # let err_msg = "I'm a teapot";
+    /// foo.unwrap_or_else(|| panic!("Err {}: {}", err_code, err_msg));
     /// ```
     pub EXPECT_FUN_CALL,
     perf,
diff --git a/clippy_lints/src/misc.rs b/clippy_lints/src/misc.rs
index d89f886a39b..ae339021a7e 100644
--- a/clippy_lints/src/misc.rs
+++ b/clippy_lints/src/misc.rs
@@ -101,7 +101,9 @@ declare_clippy_lint! {
     ///
     /// **Example:**
     /// ```rust
-    /// x.to_owned() == y
+    /// # let x = "foo";
+    /// # let y = String::from("foo");
+    /// if x.to_owned() == y {}
     /// ```
     pub CMP_OWNED,
     perf,
diff --git a/clippy_lints/src/mutex_atomic.rs b/clippy_lints/src/mutex_atomic.rs
index 3b9641b354f..bf76e0ff369 100644
--- a/clippy_lints/src/mutex_atomic.rs
+++ b/clippy_lints/src/mutex_atomic.rs
@@ -22,6 +22,8 @@ declare_clippy_lint! {
     ///
     /// **Example:**
     /// ```rust
+    /// # use std::sync::Mutex;
+    /// # let y = 1;
     /// let x = Mutex::new(&y);
     /// ```
     pub MUTEX_ATOMIC,
diff --git a/clippy_lints/src/slow_vector_initialization.rs b/clippy_lints/src/slow_vector_initialization.rs
index dde9412c52e..7e543bfe60f 100644
--- a/clippy_lints/src/slow_vector_initialization.rs
+++ b/clippy_lints/src/slow_vector_initialization.rs
@@ -19,6 +19,8 @@ declare_clippy_lint! {
     ///
     /// **Example:**
     /// ```rust
+    /// # use core::iter::repeat;
+    /// # let len = 4;
     /// let mut vec1 = Vec::with_capacity(len);
     /// vec1.resize(len, 0);
     ///
diff --git a/clippy_lints/src/trivially_copy_pass_by_ref.rs b/clippy_lints/src/trivially_copy_pass_by_ref.rs
index 4e07a07ccc2..be79fc2fb81 100644
--- a/clippy_lints/src/trivially_copy_pass_by_ref.rs
+++ b/clippy_lints/src/trivially_copy_pass_by_ref.rs
@@ -39,14 +39,15 @@ declare_clippy_lint! {
     /// each other.
     ///
     /// **Example:**
+    ///
+    /// ```rust
+    /// // Bad
+    /// fn foo(v: &u32) {}
+    /// ```
+    ///
     /// ```rust
-    /// fn foo(v: &u32) {
-    ///     assert_eq!(v, 42);
-    /// }
-    /// // should be
-    /// fn foo(v: u32) {
-    ///     assert_eq!(v, 42);
-    /// }
+    /// // Better
+    /// fn foo(v: u32) {}
     /// ```
     pub TRIVIALLY_COPY_PASS_BY_REF,
     perf,