From 0b867cf5f61a29e6710083eb8e89a819911cefe6 Mon Sep 17 00:00:00 2001
From: Samuel Tardieu <sam@rfc1149.net>
Date: Sat, 30 Nov 2024 21:40:26 +0100
Subject: [PATCH] Add `Iterator::map` to `useless_conversion`

---
 clippy_lints/src/useless_conversion.rs |  3 +++
 tests/ui/useless_conversion.fixed      |  8 +++++++-
 tests/ui/useless_conversion.rs         |  8 +++++++-
 tests/ui/useless_conversion.stderr     | 14 +++++++++++++-
 4 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/clippy_lints/src/useless_conversion.rs b/clippy_lints/src/useless_conversion.rs
index 8bf8004ef876..ccf04ab50f20 100644
--- a/clippy_lints/src/useless_conversion.rs
+++ b/clippy_lints/src/useless_conversion.rs
@@ -433,5 +433,8 @@ fn has_eligible_receiver(cx: &LateContext<'_>, recv: &Expr<'_>, expr: &Expr<'_>)
             return true;
         }
     }
+    if is_trait_method(cx, expr, sym::Iterator) {
+        return true;
+    }
     false
 }
diff --git a/tests/ui/useless_conversion.fixed b/tests/ui/useless_conversion.fixed
index 1d2fdc90419c..2f7edd92bb7c 100644
--- a/tests/ui/useless_conversion.fixed
+++ b/tests/ui/useless_conversion.fixed
@@ -328,11 +328,17 @@ fn direct_application() {
             Self
         }
     }
+    let _: Vec<u32> = [1u32].into_iter().collect();
+    //~^ useless_conversion
 
     // No lint for those
     let _: Result<Absorb, std::io::Error> = test_issue_3913().map(Into::into);
     let _: Result<(), Absorb> = test_issue_3913().map_err(Into::into);
     let _: Result<Absorb, std::io::Error> = test_issue_3913().map(From::from);
     let _: Result<(), Absorb> = test_issue_3913().map_err(From::from);
-    let _: Vec<u32> = [1u32].into_iter().map(Into::into).collect();
+}
+
+fn gen_identity<T>(x: [T; 3]) -> Vec<T> {
+    x.into_iter().collect()
+    //~^ useless_conversion
 }
diff --git a/tests/ui/useless_conversion.rs b/tests/ui/useless_conversion.rs
index 3719dc6c3fbe..eacdf77f9052 100644
--- a/tests/ui/useless_conversion.rs
+++ b/tests/ui/useless_conversion.rs
@@ -328,11 +328,17 @@ fn direct_application() {
             Self
         }
     }
+    let _: Vec<u32> = [1u32].into_iter().map(Into::into).collect();
+    //~^ useless_conversion
 
     // No lint for those
     let _: Result<Absorb, std::io::Error> = test_issue_3913().map(Into::into);
     let _: Result<(), Absorb> = test_issue_3913().map_err(Into::into);
     let _: Result<Absorb, std::io::Error> = test_issue_3913().map(From::from);
     let _: Result<(), Absorb> = test_issue_3913().map_err(From::from);
-    let _: Vec<u32> = [1u32].into_iter().map(Into::into).collect();
+}
+
+fn gen_identity<T>(x: [T; 3]) -> Vec<T> {
+    x.into_iter().map(Into::into).collect()
+    //~^ useless_conversion
 }
diff --git a/tests/ui/useless_conversion.stderr b/tests/ui/useless_conversion.stderr
index f1e18f6b0031..6aeb382902ba 100644
--- a/tests/ui/useless_conversion.stderr
+++ b/tests/ui/useless_conversion.stderr
@@ -262,5 +262,17 @@ error: useless conversion to the same type: `()`
 LL |     let _: ControlFlow<()> = c.map_continue(Into::into);
    |                               ^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing
 
-error: aborting due to 34 previous errors
+error: useless conversion to the same type: `u32`
+  --> tests/ui/useless_conversion.rs:331:41
+   |
+LL |     let _: Vec<u32> = [1u32].into_iter().map(Into::into).collect();
+   |                                         ^^^^^^^^^^^^^^^^ help: consider removing
+
+error: useless conversion to the same type: `T`
+  --> tests/ui/useless_conversion.rs:342:18
+   |
+LL |     x.into_iter().map(Into::into).collect()
+   |                  ^^^^^^^^^^^^^^^^ help: consider removing
+
+error: aborting due to 36 previous errors