From 95cabfd7227d5dc70d1ec370da3173e92447a476 Mon Sep 17 00:00:00 2001
From: Jeroen Vannevel <jer_vannevel@outlook.com>
Date: Tue, 4 Jan 2022 01:48:08 +0000
Subject: [PATCH 1/3] Correctly pass through mutable references when extracting
 a function

---
 .../src/handlers/extract_function.rs          | 39 ++++++++++++++++++-
 1 file changed, 38 insertions(+), 1 deletion(-)

diff --git a/crates/ide_assists/src/handlers/extract_function.rs b/crates/ide_assists/src/handlers/extract_function.rs
index 63b0a91ce5a..8c7fb03f7af 100644
--- a/crates/ide_assists/src/handlers/extract_function.rs
+++ b/crates/ide_assists/src/handlers/extract_function.rs
@@ -878,7 +878,7 @@ impl FunctionBody {
                 // We can move the value into the function call if it's not used after the call,
                 // if the var is not used but defined outside a loop we are extracting from we can't move it either
                 // as the function will reuse it in the next iteration.
-                let move_local = !has_usages && defined_outside_parent_loop;
+                let move_local = (!has_usages && defined_outside_parent_loop) || ty.is_reference();
                 Param { var, ty, move_local, requires_mut, is_copy }
             })
             .collect()
@@ -4332,6 +4332,43 @@ fn foo() {
 fn $0fun_name(a: _) -> _ {
     a
 }
+"#,
+        );
+    }
+
+    #[test]
+    fn test_jeroen() {
+        check_assist(
+            extract_function,
+            r#"
+pub struct Foo {
+    field: u32,
+}
+
+pub fn testfn(arg: &mut Foo) {
+    $0arg.field = 8; // write access
+    println!("{}", arg.field); // read access$0
+    // Simulating access after the extracted portion
+    arg.field = 16; // write access
+    println!("{}", arg.field); // read access
+}
+"#,
+            r#"
+pub struct Foo {
+    field: u32,
+}
+
+pub fn testfn(arg: &mut Foo) {
+    fun_name(arg); // read access
+    // Simulating access after the extracted portion
+    arg.field = 16; // write access
+    println!("{}", arg.field); // read access
+}
+
+fn $0fun_name(arg: &mut Foo) {
+    arg.field = 8;
+    println!("{}", arg.field);
+}
 "#,
         );
     }

From 5beddf93e75ab1d001fc2382830cea560b1473fd Mon Sep 17 00:00:00 2001
From: Jeroen Vannevel <jer_vannevel@outlook.com>
Date: Tue, 4 Jan 2022 02:12:53 +0000
Subject: [PATCH 2/3] additional test without further usages

---
 .../src/handlers/extract_function.rs          | 33 ++++++++++++++++++-
 1 file changed, 32 insertions(+), 1 deletion(-)

diff --git a/crates/ide_assists/src/handlers/extract_function.rs b/crates/ide_assists/src/handlers/extract_function.rs
index 8c7fb03f7af..2821f6cde98 100644
--- a/crates/ide_assists/src/handlers/extract_function.rs
+++ b/crates/ide_assists/src/handlers/extract_function.rs
@@ -4337,7 +4337,7 @@ fn $0fun_name(a: _) -> _ {
     }
 
     #[test]
-    fn test_jeroen() {
+    fn reference_mutable_param_with_further_usages() {
         check_assist(
             extract_function,
             r#"
@@ -4365,6 +4365,37 @@ pub fn testfn(arg: &mut Foo) {
     println!("{}", arg.field); // read access
 }
 
+fn $0fun_name(arg: &mut Foo) {
+    arg.field = 8;
+    println!("{}", arg.field);
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn reference_mutable_param_without_further_usages() {
+        check_assist(
+            extract_function,
+            r#"
+pub struct Foo {
+    field: u32,
+}
+
+pub fn testfn(arg: &mut Foo) {
+    $0arg.field = 8; // write access
+    println!("{}", arg.field); // read access$0
+}
+"#,
+            r#"
+pub struct Foo {
+    field: u32,
+}
+
+pub fn testfn(arg: &mut Foo) {
+    fun_name(arg); // read access
+}
+
 fn $0fun_name(arg: &mut Foo) {
     arg.field = 8;
     println!("{}", arg.field);

From ec61abbe930ae07b2a89813e37d595de1d47b288 Mon Sep 17 00:00:00 2001
From: Jeroen Vannevel <jer_vannevel@outlook.com>
Date: Tue, 4 Jan 2022 10:11:04 +0000
Subject: [PATCH 3/3] reduced the tests to their bare essence

---
 .../src/handlers/extract_function.rs           | 18 ++++++------------
 1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/crates/ide_assists/src/handlers/extract_function.rs b/crates/ide_assists/src/handlers/extract_function.rs
index 2821f6cde98..59c52dcd04a 100644
--- a/crates/ide_assists/src/handlers/extract_function.rs
+++ b/crates/ide_assists/src/handlers/extract_function.rs
@@ -4346,11 +4346,9 @@ pub struct Foo {
 }
 
 pub fn testfn(arg: &mut Foo) {
-    $0arg.field = 8; // write access
-    println!("{}", arg.field); // read access$0
+    $0arg.field = 8;$0
     // Simulating access after the extracted portion
-    arg.field = 16; // write access
-    println!("{}", arg.field); // read access
+    arg.field = 16;
 }
 "#,
             r#"
@@ -4359,15 +4357,13 @@ pub struct Foo {
 }
 
 pub fn testfn(arg: &mut Foo) {
-    fun_name(arg); // read access
+    fun_name(arg);
     // Simulating access after the extracted portion
-    arg.field = 16; // write access
-    println!("{}", arg.field); // read access
+    arg.field = 16;
 }
 
 fn $0fun_name(arg: &mut Foo) {
     arg.field = 8;
-    println!("{}", arg.field);
 }
 "#,
         );
@@ -4383,8 +4379,7 @@ pub struct Foo {
 }
 
 pub fn testfn(arg: &mut Foo) {
-    $0arg.field = 8; // write access
-    println!("{}", arg.field); // read access$0
+    $0arg.field = 8;$0
 }
 "#,
             r#"
@@ -4393,12 +4388,11 @@ pub struct Foo {
 }
 
 pub fn testfn(arg: &mut Foo) {
-    fun_name(arg); // read access
+    fun_name(arg);
 }
 
 fn $0fun_name(arg: &mut Foo) {
     arg.field = 8;
-    println!("{}", arg.field);
 }
 "#,
         );