From 7f71000c12248b0d19833dcd749ca1ec5871dda3 Mon Sep 17 00:00:00 2001
From: Maan2003 <manmeetmann2003@gmail.com>
Date: Fri, 11 Jun 2021 12:24:56 +0530
Subject: Don't suggest Remove unused param in trait impls

---
 .../src/handlers/remove_unused_param.rs            | 30 +++++++++++++++++++++-
 1 file changed, 29 insertions(+), 1 deletion(-)

diff --git a/crates/ide_assists/src/handlers/remove_unused_param.rs b/crates/ide_assists/src/handlers/remove_unused_param.rs
index 2699d2861..fabfe7e93 100644
--- a/crates/ide_assists/src/handlers/remove_unused_param.rs
+++ b/crates/ide_assists/src/handlers/remove_unused_param.rs
@@ -37,8 +37,20 @@ pub(crate) fn remove_unused_param(acc: &mut Assists, ctx: &AssistContext) -> Opt
         _ => return None,
     };
     let func = param.syntax().ancestors().find_map(ast::Fn::cast)?;
-    let param_position = func.param_list()?.params().position(|it| it == param)?;
 
+    // check if fn is in impl Trait for ..
+    if func
+        .syntax()
+        .parent() // AssocItemList
+        .and_then(|x| x.parent())
+        .and_then(ast::Impl::cast)
+        .map_or(false, |imp| imp.trait_().is_some())
+    {
+        cov_mark::hit!(trait_impl);
+        return None;
+    }
+
+    let param_position = func.param_list()?.params().position(|it| it == param)?;
     let fn_def = {
         let func = ctx.sema.to_def(&func)?;
         Definition::ModuleDef(func.into())
@@ -253,6 +265,22 @@ fn main() { foo(9, 2) }
         );
     }
 
+    #[test]
+    fn trait_impl() {
+        cov_mark::check!(trait_impl);
+        check_assist_not_applicable(
+            remove_unused_param,
+            r#"
+trait Trait {
+    fn foo(x: i32);
+}
+impl Trait for () {
+    fn foo($0x: i32) {}
+}
+"#,
+        );
+    }
+
     #[test]
     fn remove_across_files() {
         check_assist(
-- 
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