From 243661b739b122f51a17e64161d9f3a1324b8d6a Mon Sep 17 00:00:00 2001
From: hrxi <hrrrxi@gmail.com>
Date: Sat, 12 Nov 2022 22:26:09 +0100
Subject: [PATCH] Make it clear that `or_fun_call` can be a false-positive

Also move it to nursery so that the false-positives can be dealt with.

CC #8574
---
 clippy_lints/src/methods/mod.rs | 22 ++++++++++------------
 tests/ui/unwrap_or.rs           |  2 +-
 2 files changed, 11 insertions(+), 13 deletions(-)

diff --git a/clippy_lints/src/methods/mod.rs b/clippy_lints/src/methods/mod.rs
index 82a2cc62d820..53f9c355c5d7 100644
--- a/clippy_lints/src/methods/mod.rs
+++ b/clippy_lints/src/methods/mod.rs
@@ -832,32 +832,30 @@ declare_clippy_lint! {
     /// etc. instead.
     ///
     /// ### Why is this bad?
-    /// The function will always be called and potentially
-    /// allocate an object acting as the default.
+    /// The function will always be called. This is only bad if it allocates or
+    /// does some non-trivial amount of work.
     ///
     /// ### Known problems
-    /// If the function has side-effects, not calling it will
-    /// change the semantic of the program, but you shouldn't rely on that anyway.
+    /// If the function has side-effects, not calling it will change the
+    /// semantic of the program, but you shouldn't rely on that.
+    ///
+    /// The lint also cannot figure out whether the function you call is
+    /// actually expensive to call or not.
     ///
     /// ### Example
     /// ```rust
     /// # let foo = Some(String::new());
-    /// foo.unwrap_or(String::new());
+    /// foo.unwrap_or(String::from("empty"));
     /// ```
     ///
     /// Use instead:
     /// ```rust
     /// # let foo = Some(String::new());
-    /// foo.unwrap_or_else(String::new);
-    ///
-    /// // or
-    ///
-    /// # let foo = Some(String::new());
-    /// foo.unwrap_or_default();
+    /// foo.unwrap_or_else(|| String::from("empty"));
     /// ```
     #[clippy::version = "pre 1.29.0"]
     pub OR_FUN_CALL,
-    perf,
+    nursery,
     "using any `*or` method with a function call, which suggests `*or_else`"
 }
 
diff --git a/tests/ui/unwrap_or.rs b/tests/ui/unwrap_or.rs
index bfb41e439473..a0c003f5b1ea 100644
--- a/tests/ui/unwrap_or.rs
+++ b/tests/ui/unwrap_or.rs
@@ -1,4 +1,4 @@
-#![warn(clippy::all)]
+#![warn(clippy::all, clippy::or_fun_call)]
 
 fn main() {
     let s = Some(String::from("test string")).unwrap_or("Fail".to_string()).len();