Add getter/setter assists

Finish implementing `generate_setter` assists

Make `generate_impl_text` util generic

generate getter methods

Fix getter / setter naming

It's now in-line with the Rust API naming guidelines: https://rust-lang.github.io/api-guidelines/naming.html#getter-names-follow-rust-convention-c-getter

apply clippy

Improve examples

9 files changed, 603 insertions, 68 deletions

diff --git a/crates/assists/src/handlers/generate_enum_match_method.rs b/crates/assists/src/handlers/generate_enum_match_method.rs
index 9d6b161c9..c3ff38b66 100644
--- a/crates/assists/src/handlers/generate_enum_match_method.rs
+++ b/crates/assists/src/handlers/generate_enum_match_method.rs
@@ -4,7 +4,7 @@ use syntax::ast::{self, AstNode, NameOwner};
 use test_utils::mark;
 
 use crate::{
-    utils::{find_impl_block, find_struct_impl},
+    utils::{find_impl_block, find_struct_impl, generate_impl_text},
     AssistContext, AssistId, AssistKind, Assists,
 };
 
@@ -82,7 +82,7 @@ pub(crate) fn generate_enum_match_method(acc: &mut Assists, ctx: &AssistContext)
             let start_offset = impl_def
                 .and_then(|impl_def| find_impl_block(impl_def, &mut buf))
                 .unwrap_or_else(|| {
-                    buf = generate_impl_text(&parent_enum, &buf);
+                    buf = generate_impl_text(&ast::Adt::Enum(parent_enum.clone()), &buf);
                     parent_enum.syntax().text_range().end()
                 });
 
@@ -91,16 +91,6 @@ pub(crate) fn generate_enum_match_method(acc: &mut Assists, ctx: &AssistContext)
     )
 }
 
-// Generates the surrounding `impl Type { <code> }` including type and lifetime
-// parameters
-fn generate_impl_text(strukt: &ast::Enum, code: &str) -> String {
-    let mut buf = String::with_capacity(code.len());
-    buf.push_str("\n\nimpl ");
-    buf.push_str(strukt.name().unwrap().text());
-    format_to!(buf, " {{\n{}\n}}", code);
-    buf
-}
-
 #[cfg(test)]
 mod tests {
     use test_utils::mark;
diff --git a/crates/assists/src/handlers/generate_getter.rs b/crates/assists/src/handlers/generate_getter.rs
new file mode 100644
index 000000000..b63dfce41
--- /dev/null
+++ b/crates/assists/src/handlers/generate_getter.rs
@@ -0,0 +1,156 @@
+use stdx::{format_to, to_lower_snake_case};
+use syntax::ast::VisibilityOwner;
+use syntax::ast::{self, AstNode, NameOwner};
+
+use crate::{
+    utils::{find_impl_block, find_struct_impl, generate_impl_text},
+    AssistContext, AssistId, AssistKind, Assists,
+};
+
+// Assist: generate_getter
+//
+// Generate a getter method.
+//
+// ```
+// struct Person {
+//     nam$0e: String,
+// }
+// ```
+// ->
+// ```
+// struct Person {
+//     name: String,
+// }
+//
+// impl Person {
+//     /// Get a reference to the person's name.
+//     fn name(&self) -> &String {
+//         &self.name
+//     }
+// }
+// ```
+pub(crate) fn generate_getter(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
+    let strukt = ctx.find_node_at_offset::<ast::Struct>()?;
+    let field = ctx.find_node_at_offset::<ast::RecordField>()?;
+
+    let strukt_name = strukt.name()?;
+    let field_name = field.name()?;
+    let field_ty = field.ty()?;
+
+    // Return early if we've found an existing fn
+    let fn_name = to_lower_snake_case(&field_name.to_string());
+    let impl_def = find_struct_impl(&ctx, &ast::Adt::Struct(strukt.clone()), fn_name.as_str())?;
+
+    let target = field.syntax().text_range();
+    acc.add(
+        AssistId("generate_getter", AssistKind::Generate),
+        "Generate a getter method",
+        target,
+        |builder| {
+            let mut buf = String::with_capacity(512);
+
+            let fn_name_spaced = fn_name.replace('_', " ");
+            let strukt_name_spaced =
+                to_lower_snake_case(&strukt_name.to_string()).replace('_', " ");
+
+            if impl_def.is_some() {
+                buf.push('\n');
+            }
+
+            let vis = strukt.visibility().map_or(String::new(), |v| format!("{} ", v));
+            format_to!(
+                buf,
+                "    /// Get a reference to the {}'s {}.
+    {}fn {}(&self) -> &{} {{
+        &self.{}
+    }}",
+                strukt_name_spaced,
+                fn_name_spaced,
+                vis,
+                fn_name,
+                field_ty,
+                fn_name,
+            );
+
+            let start_offset = impl_def
+                .and_then(|impl_def| find_impl_block(impl_def, &mut buf))
+                .unwrap_or_else(|| {
+                    buf = generate_impl_text(&ast::Adt::Struct(strukt.clone()), &buf);
+                    strukt.syntax().text_range().end()
+                });
+
+            builder.insert(start_offset, buf);
+        },
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tests::{check_assist, check_assist_not_applicable};
+
+    use super::*;
+
+    fn check_not_applicable(ra_fixture: &str) {
+        check_assist_not_applicable(generate_getter, ra_fixture)
+    }
+
+    #[test]
+    fn test_generate_getter_from_field() {
+        check_assist(
+            generate_getter,
+            r#"
+struct Context<T: Clone> {
+    dat$0a: T,
+}"#,
+            r#"
+struct Context<T: Clone> {
+    data: T,
+}
+
+impl<T: Clone> Context<T> {
+    /// Get a reference to the context's data.
+    fn data(&self) -> &T {
+        &self.data
+    }
+}"#,
+        );
+    }
+
+    #[test]
+    fn test_generate_getter_already_implemented() {
+        check_not_applicable(
+            r#"
+struct Context<T: Clone> {
+    dat$0a: T,
+}
+
+impl<T: Clone> Context<T> {
+    fn data(&self) -> &T {
+        &self.data
+    }
+}"#,
+        );
+    }
+
+    #[test]
+    fn test_generate_getter_from_field_with_visibility_marker() {
+        check_assist(
+            generate_getter,
+            r#"
+pub(crate) struct Context<T: Clone> {
+    dat$0a: T,
+}"#,
+            r#"
+pub(crate) struct Context<T: Clone> {
+    data: T,
+}
+
+impl<T: Clone> Context<T> {
+    /// Get a reference to the context's data.
+    pub(crate) fn data(&self) -> &T {
+        &self.data
+    }
+}"#,
+        );
+    }
+}
diff --git a/crates/assists/src/handlers/generate_getter_mut.rs b/crates/assists/src/handlers/generate_getter_mut.rs
new file mode 100644
index 000000000..b5085035e
--- /dev/null
+++ b/crates/assists/src/handlers/generate_getter_mut.rs
@@ -0,0 +1,159 @@
+use stdx::{format_to, to_lower_snake_case};
+use syntax::ast::VisibilityOwner;
+use syntax::ast::{self, AstNode, NameOwner};
+
+use crate::{
+    utils::{find_impl_block, find_struct_impl, generate_impl_text},
+    AssistContext, AssistId, AssistKind, Assists,
+};
+
+// Assist: generate_getter_mut
+//
+// Generate a mut getter method.
+//
+// ```
+// struct Person {
+//     nam$0e: String,
+// }
+// ```
+// ->
+// ```
+// struct Person {
+//     name: String,
+// }
+//
+// impl Person {
+//     /// Get a mutable reference to the person's name.
+//     fn name_mut(&mut self) -> &mut String {
+//         &mut self.name
+//     }
+// }
+// ```
+pub(crate) fn generate_getter_mut(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
+    let strukt = ctx.find_node_at_offset::<ast::Struct>()?;
+    let field = ctx.find_node_at_offset::<ast::RecordField>()?;
+
+    let strukt_name = strukt.name()?;
+    let field_name = field.name()?;
+    let field_ty = field.ty()?;
+
+    // Return early if we've found an existing fn
+    let fn_name = to_lower_snake_case(&field_name.to_string());
+    let impl_def = find_struct_impl(
+        &ctx,
+        &ast::Adt::Struct(strukt.clone()),
+        format!("{}_mut", fn_name).as_str(),
+    )?;
+
+    let target = field.syntax().text_range();
+    acc.add(
+        AssistId("generate_getter_mut", AssistKind::Generate),
+        "Generate a mut getter method",
+        target,
+        |builder| {
+            let mut buf = String::with_capacity(512);
+            let fn_name_spaced = fn_name.replace('_', " ");
+            let strukt_name_spaced =
+                to_lower_snake_case(&strukt_name.to_string()).replace('_', " ");
+
+            if impl_def.is_some() {
+                buf.push('\n');
+            }
+
+            let vis = strukt.visibility().map_or(String::new(), |v| format!("{} ", v));
+            format_to!(
+                buf,
+                "    /// Get a mutable reference to the {}'s {}.
+    {}fn {}_mut(&mut self) -> &mut {} {{
+        &mut self.{}
+    }}",
+                strukt_name_spaced,
+                fn_name_spaced,
+                vis,
+                fn_name,
+                field_ty,
+                fn_name,
+            );
+
+            let start_offset = impl_def
+                .and_then(|impl_def| find_impl_block(impl_def, &mut buf))
+                .unwrap_or_else(|| {
+                    buf = generate_impl_text(&ast::Adt::Struct(strukt.clone()), &buf);
+                    strukt.syntax().text_range().end()
+                });
+
+            builder.insert(start_offset, buf);
+        },
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tests::{check_assist, check_assist_not_applicable};
+
+    use super::*;
+
+    fn check_not_applicable(ra_fixture: &str) {
+        check_assist_not_applicable(generate_getter_mut, ra_fixture)
+    }
+
+    #[test]
+    fn test_generate_getter_mut_from_field() {
+        check_assist(
+            generate_getter_mut,
+            r#"
+struct Context<T: Clone> {
+    dat$0a: T,
+}"#,
+            r#"
+struct Context<T: Clone> {
+    data: T,
+}
+
+impl<T: Clone> Context<T> {
+    /// Get a mutable reference to the context's data.
+    fn data_mut(&mut self) -> &mut T {
+        &mut self.data
+    }
+}"#,
+        );
+    }
+
+    #[test]
+    fn test_generate_getter_mut_already_implemented() {
+        check_not_applicable(
+            r#"
+struct Context<T: Clone> {
+    dat$0a: T,
+}
+
+impl<T: Clone> Context<T> {
+    fn data_mut(&mut self) -> &mut T {
+        &mut self.data
+    }
+}"#,
+        );
+    }
+
+    #[test]
+    fn test_generate_getter_mut_from_field_with_visibility_marker() {
+        check_assist(
+            generate_getter_mut,
+            r#"
+pub(crate) struct Context<T: Clone> {
+    dat$0a: T,
+}"#,
+            r#"
+pub(crate) struct Context<T: Clone> {
+    data: T,
+}
+
+impl<T: Clone> Context<T> {
+    /// Get a mutable reference to the context's data.
+    pub(crate) fn data_mut(&mut self) -> &mut T {
+        &mut self.data
+    }
+}"#,
+        );
+    }
+}
diff --git a/crates/assists/src/handlers/generate_new.rs b/crates/assists/src/handlers/generate_new.rs
index a9203d33f..c29077225 100644
--- a/crates/assists/src/handlers/generate_new.rs
+++ b/crates/assists/src/handlers/generate_new.rs
@@ -1,12 +1,10 @@
+use ast::Adt;
 use itertools::Itertools;
 use stdx::format_to;
-use syntax::{
-    ast::{self, AstNode, GenericParamsOwner, NameOwner, StructKind, VisibilityOwner},
-    SmolStr,
-};
+use syntax::ast::{self, AstNode, NameOwner, StructKind, VisibilityOwner};
 
 use crate::{
-    utils::{find_impl_block, find_struct_impl},
+    utils::{find_impl_block, find_struct_impl, generate_impl_text},
     AssistContext, AssistId, AssistKind, Assists,
 };
 
@@ -28,7 +26,6 @@ use crate::{
 // impl<T: Clone> Ctx<T> {
 //     fn $0new(data: T) -> Self { Self { data } }
 // }
-//
 // ```
 pub(crate) fn generate_new(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
     let strukt = ctx.find_node_at_offset::<ast::Struct>()?;
@@ -40,7 +37,7 @@ pub(crate) fn generate_new(acc: &mut Assists, ctx: &AssistContext) -> Option<()>
     };
 
     // Return early if we've found an existing new fn
-    let impl_def = find_struct_impl(&ctx, &ast::Adt::Struct(strukt.clone()), "new")?;
+    let impl_def = find_struct_impl(&ctx, &Adt::Struct(strukt.clone()), "new")?;
 
     let target = strukt.syntax().text_range();
     acc.add(AssistId("generate_new", AssistKind::Generate), "Generate `new`", target, |builder| {
@@ -63,7 +60,7 @@ pub(crate) fn generate_new(acc: &mut Assists, ctx: &AssistContext) -> Option<()>
         let start_offset = impl_def
             .and_then(|impl_def| find_impl_block(impl_def, &mut buf))
             .unwrap_or_else(|| {
-                buf = generate_impl_text(&strukt, &buf);
+                buf = generate_impl_text(&Adt::Struct(strukt.clone()), &buf);
                 strukt.syntax().text_range().end()
             });
 
@@ -77,32 +74,6 @@ pub(crate) fn generate_new(acc: &mut Assists, ctx: &AssistContext) -> Option<()>
     })
 }
 
-// Generates the surrounding `impl Type { <code> }` including type and lifetime
-// parameters
-fn generate_impl_text(strukt: &ast::Struct, code: &str) -> String {
-    let type_params = strukt.generic_param_list();
-    let mut buf = String::with_capacity(code.len());
-    buf.push_str("\n\nimpl");
-    if let Some(type_params) = &type_params {
-        format_to!(buf, "{}", type_params.syntax());
-    }
-    buf.push(' ');
-    buf.push_str(strukt.name().unwrap().text());
-    if let Some(type_params) = type_params {
-        let lifetime_params = type_params
-            .lifetime_params()
-            .filter_map(|it| it.lifetime())
-            .map(|it| SmolStr::from(it.text()));
-        let type_params =
-            type_params.type_params().filter_map(|it| it.name()).map(|it| SmolStr::from(it.text()));
-        format_to!(buf, "<{}>", lifetime_params.chain(type_params).format(", "))
-    }
-
-    format_to!(buf, " {{\n{}\n}}\n", code);
-
-    buf
-}
-
 #[cfg(test)]
 mod tests {
     use crate::tests::{check_assist, check_assist_not_applicable, check_assist_target};
@@ -120,8 +91,7 @@ mod tests {
 
 impl Foo {
     fn $0new() -> Self { Self {  } }
-}
-",
+}",
         );
         check_assist(
             generate_new,
@@ -130,8 +100,7 @@ impl Foo {
 
 impl<T: Clone> Foo<T> {
     fn $0new() -> Self { Self {  } }
-}
-",
+}",
         );
         check_assist(
             generate_new,
@@ -140,8 +109,7 @@ impl<T: Clone> Foo<T> {
 
 impl<'a, T: Foo<'a>> Foo<'a, T> {
     fn $0new() -> Self { Self {  } }
-}
-",
+}",
         );
         check_assist(
             generate_new,
@@ -150,8 +118,7 @@ impl<'a, T: Foo<'a>> Foo<'a, T> {
 
 impl Foo {
     fn $0new(baz: String) -> Self { Self { baz } }
-}
-",
+}",
         );
         check_assist(
             generate_new,
@@ -160,8 +127,7 @@ impl Foo {
 
 impl Foo {
     fn $0new(baz: String, qux: Vec<i32>) -> Self { Self { baz, qux } }
-}
-",
+}",
         );
 
         // Check that visibility modifiers don't get brought in for fields
@@ -172,8 +138,7 @@ impl Foo {
 
 impl Foo {
     fn $0new(baz: String, qux: Vec<i32>) -> Self { Self { baz, qux } }
-}
-",
+}",
         );
 
         // Check that it reuses existing impls
@@ -240,8 +205,7 @@ impl Foo {
 
 impl Foo {
     pub fn $0new() -> Self { Self {  } }
-}
-",
+}",
         );
         check_assist(
             generate_new,
@@ -250,8 +214,7 @@ impl Foo {
 
 impl Foo {
     pub(crate) fn $0new() -> Self { Self {  } }
-}
-",
+}",
         );
     }
 
@@ -322,8 +285,7 @@ impl<T> Source<T> {
     pub fn map<F: FnOnce(T) -> U, U>(self, f: F) -> Source<U> {
         Source { file_id: self.file_id, ast: f(self.ast) }
     }
-}
-"##,
+}"##,
             r##"
 pub struct AstId<N: AstNode> {
     file_id: HirFileId,
@@ -347,8 +309,7 @@ impl<T> Source<T> {
     pub fn map<F: FnOnce(T) -> U, U>(self, f: F) -> Source<U> {
         Source { file_id: self.file_id, ast: f(self.ast) }
     }
-}
-"##,
+}"##,
         );
     }
 }
diff --git a/crates/assists/src/handlers/generate_setter.rs b/crates/assists/src/handlers/generate_setter.rs
new file mode 100644
index 000000000..c9043a162
--- /dev/null
+++ b/crates/assists/src/handlers/generate_setter.rs
@@ -0,0 +1,162 @@
+use stdx::{format_to, to_lower_snake_case};
+use syntax::ast::VisibilityOwner;
+use syntax::ast::{self, AstNode, NameOwner};
+
+use crate::{
+    utils::{find_impl_block, find_struct_impl, generate_impl_text},
+    AssistContext, AssistId, AssistKind, Assists,
+};
+
+// Assist: generate_setter
+//
+// Generate a setter method.
+//
+// ```
+// struct Person {
+//     nam$0e: String,
+// }
+// ```
+// ->
+// ```
+// struct Person {
+//     name: String,
+// }
+//
+// impl Person {
+//     /// Set the person's name.
+//     fn set_name(&mut self, name: String) {
+//         self.name = name;
+//     }
+// }
+// ```
+pub(crate) fn generate_setter(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
+    let strukt = ctx.find_node_at_offset::<ast::Struct>()?;
+    let field = ctx.find_node_at_offset::<ast::RecordField>()?;
+
+    let strukt_name = strukt.name()?;
+    let field_name = field.name()?;
+    let field_ty = field.ty()?;
+
+    // Return early if we've found an existing fn
+    let fn_name = to_lower_snake_case(&field_name.to_string());
+    let impl_def = find_struct_impl(
+        &ctx,
+        &ast::Adt::Struct(strukt.clone()),
+        format!("set_{}", fn_name).as_str(),
+    )?;
+
+    let target = field.syntax().text_range();
+    acc.add(
+        AssistId("generate_setter", AssistKind::Generate),
+        "Generate a setter method",
+        target,
+        |builder| {
+            let mut buf = String::with_capacity(512);
+
+            let fn_name_spaced = fn_name.replace('_', " ");
+            let strukt_name_spaced =
+                to_lower_snake_case(&strukt_name.to_string()).replace('_', " ");
+
+            if impl_def.is_some() {
+                buf.push('\n');
+            }
+
+            let vis = strukt.visibility().map_or(String::new(), |v| format!("{} ", v));
+            format_to!(
+                buf,
+                "    /// Set the {}'s {}.
+    {}fn set_{}(&mut self, {}: {}) {{
+        self.{} = {};
+    }}",
+                strukt_name_spaced,
+                fn_name_spaced,
+                vis,
+                fn_name,
+                fn_name,
+                field_ty,
+                fn_name,
+                fn_name,
+            );
+
+            let start_offset = impl_def
+                .and_then(|impl_def| find_impl_block(impl_def, &mut buf))
+                .unwrap_or_else(|| {
+                    buf = generate_impl_text(&ast::Adt::Struct(strukt.clone()), &buf);
+                    strukt.syntax().text_range().end()
+                });
+
+            builder.insert(start_offset, buf);
+        },
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tests::{check_assist, check_assist_not_applicable};
+
+    use super::*;
+
+    fn check_not_applicable(ra_fixture: &str) {
+        check_assist_not_applicable(generate_setter, ra_fixture)
+    }
+
+    #[test]
+    fn test_generate_setter_from_field() {
+        check_assist(
+            generate_setter,
+            r#"
+struct Person<T: Clone> {
+    dat$0a: T,
+}"#,
+            r#"
+struct Person<T: Clone> {
+    data: T,
+}
+
+impl<T: Clone> Person<T> {
+    /// Set the person's data.
+    fn set_data(&mut self, data: T) {
+        self.data = data;
+    }
+}"#,
+        );
+    }
+
+    #[test]
+    fn test_generate_setter_already_implemented() {
+        check_not_applicable(
+            r#"
+struct Person<T: Clone> {
+    dat$0a: T,
+}
+
+impl<T: Clone> Person<T> {
+    fn set_data(&mut self, data: T) {
+        self.data = data;
+    }
+}"#,
+        );
+    }
+
+    #[test]
+    fn test_generate_setter_from_field_with_visibility_marker() {
+        check_assist(
+            generate_setter,
+            r#"
+pub(crate) struct Person<T: Clone> {
+    dat$0a: T,
+}"#,
+            r#"
+pub(crate) struct Person<T: Clone> {
+    data: T,
+}
+
+impl<T: Clone> Person<T> {
+    /// Set the person's data.
+    pub(crate) fn set_data(&mut self, data: T) {
+        self.data = data;
+    }
+}"#,
+        );
+    }
+}
diff --git a/crates/assists/src/lib.rs b/crates/assists/src/lib.rs
index 83fbf6986..957efa6b9 100644
--- a/crates/assists/src/lib.rs
+++ b/crates/assists/src/lib.rs
@@ -130,8 +130,11 @@ mod handlers {
     mod generate_enum_match_method;
     mod generate_from_impl_for_enum;
     mod generate_function;
+    mod generate_getter;
+    mod generate_getter_mut;
     mod generate_impl;
     mod generate_new;
+    mod generate_setter;
     mod infer_function_return_type;
     mod inline_function;
     mod inline_local_variable;
@@ -189,8 +192,11 @@ mod handlers {
             generate_enum_match_method::generate_enum_match_method,
             generate_from_impl_for_enum::generate_from_impl_for_enum,
             generate_function::generate_function,
+            generate_getter::generate_getter,
+            generate_getter_mut::generate_getter_mut,
             generate_impl::generate_impl,
             generate_new::generate_new,
+            generate_setter::generate_setter,
             infer_function_return_type::infer_function_return_type,
             inline_function::inline_function,
             inline_local_variable::inline_local_variable,
diff --git a/crates/assists/src/tests.rs b/crates/assists/src/tests.rs
index 32bd8698b..1bdcb9ede 100644
--- a/crates/assists/src/tests.rs
+++ b/crates/assists/src/tests.rs
@@ -169,6 +169,9 @@ fn assist_order_field_struct() {
     let mut assists = assists.iter();
 
     assert_eq!(assists.next().expect("expected assist").label, "Change visibility to pub(crate)");
+    assert_eq!(assists.next().expect("expected assist").label, "Generate a getter method");
+    assert_eq!(assists.next().expect("expected assist").label, "Generate a mut getter method");
+    assert_eq!(assists.next().expect("expected assist").label, "Generate a setter method");
     assert_eq!(assists.next().expect("expected assist").label, "Add `#[derive]`");
 }
 
diff --git a/crates/assists/src/tests/generated.rs b/crates/assists/src/tests/generated.rs
index 0dbb05f2a..6f2b22bc2 100644
--- a/crates/assists/src/tests/generated.rs
+++ b/crates/assists/src/tests/generated.rs
@@ -534,6 +534,54 @@ fn bar(arg: &str, baz: Baz) ${0:-> ()} {
 }
 
 #[test]
+fn doctest_generate_getter() {
+    check_doc_test(
+        "generate_getter",
+        r#####"
+struct Person {
+    nam$0e: String,
+}
+"#####,
+        r#####"
+struct Person {
+    name: String,
+}
+
+impl Person {
+    /// Get a reference to the person's name.
+    fn name(&self) -> &String {
+        &self.name
+    }
+}
+"#####,
+    )
+}
+
+#[test]
+fn doctest_generate_getter_mut() {
+    check_doc_test(
+        "generate_getter_mut",
+        r#####"
+struct Person {
+    nam$0e: String,
+}
+"#####,
+        r#####"
+struct Person {
+    name: String,
+}
+
+impl Person {
+    /// Get a mutable reference to the person's name.
+    fn name_mut(&mut self) -> &mut String {
+        &mut self.name
+    }
+}
+"#####,
+    )
+}
+
+#[test]
 fn doctest_generate_impl() {
     check_doc_test(
         "generate_impl",
@@ -571,7 +619,30 @@ struct Ctx<T: Clone> {
 impl<T: Clone> Ctx<T> {
     fn $0new(data: T) -> Self { Self { data } }
 }
+"#####,
+    )
+}
 
+#[test]
+fn doctest_generate_setter() {
+    check_doc_test(
+        "generate_setter",
+        r#####"
+struct Person {
+    nam$0e: String,
+}
+"#####,
+        r#####"
+struct Person {
+    name: String,
+}
+
+impl Person {
+    /// Set the person's name.
+    fn set_name(&mut self, name: String) {
+        self.name = name;
+    }
+}
 "#####,
     )
 }
diff --git a/crates/assists/src/utils.rs b/crates/assists/src/utils.rs
index cd80c2958..643dade23 100644
--- a/crates/assists/src/utils.rs
+++ b/crates/assists/src/utils.rs
@@ -5,12 +5,13 @@ use std::ops;
 use hir::{Adt, HasSource};
 use ide_db::{helpers::SnippetCap, RootDatabase};
 use itertools::Itertools;
+use stdx::format_to;
 use syntax::{
     ast::edit::AstNodeEdit,
     ast::AttrsOwner,
     ast::NameOwner,
-    ast::{self, edit, make, ArgListOwner},
-    AstNode, Direction,
+    ast::{self, edit, make, ArgListOwner, GenericParamsOwner},
+    AstNode, Direction, SmolStr,
     SyntaxKind::*,
     SyntaxNode, TextSize, T,
 };
@@ -354,3 +355,29 @@ pub(crate) fn find_impl_block(impl_def: ast::Impl, buf: &mut String) -> Option<T
         .end();
     Some(start)
 }
+
+// Generates the surrounding `impl Type { <code> }` including type and lifetime
+// parameters
+pub(crate) fn generate_impl_text(adt: &ast::Adt, code: &str) -> String {
+    let type_params = adt.generic_param_list();
+    let mut buf = String::with_capacity(code.len());
+    buf.push_str("\n\nimpl");
+    if let Some(type_params) = &type_params {
+        format_to!(buf, "{}", type_params.syntax());
+    }
+    buf.push(' ');
+    buf.push_str(adt.name().unwrap().text());
+    if let Some(type_params) = type_params {
+        let lifetime_params = type_params
+            .lifetime_params()
+            .filter_map(|it| it.lifetime())
+            .map(|it| SmolStr::from(it.text()));
+        let type_params =
+            type_params.type_params().filter_map(|it| it.name()).map(|it| SmolStr::from(it.text()));
+        format_to!(buf, "<{}>", lifetime_params.chain(type_params).format(", "))
+    }
+
+    format_to!(buf, " {{\n{}\n}}", code);
+
+    buf
+}