25 files changed, 409 insertions, 242 deletions

diff --git a/crates/ra_assists/src/assist_config.rs b/crates/ra_assists/src/assist_config.rs
new file mode 100644
index 000000000..c0a0226fb
--- /dev/null
+++ b/crates/ra_assists/src/assist_config.rs
@@ -0,0 +1,27 @@
+//! Settings for tweaking assists.
+//!
+//! The fun thing here is `SnippetCap` -- this type can only be created in this
+//! module, and we use to statically check that we only produce snippet
+//! assists if we are allowed to.
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct AssistConfig {
+    pub snippet_cap: Option<SnippetCap>,
+}
+
+impl AssistConfig {
+    pub fn allow_snippets(&mut self, yes: bool) {
+        self.snippet_cap = if yes { Some(SnippetCap { _private: () }) } else { None }
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct SnippetCap {
+    _private: (),
+}
+
+impl Default for AssistConfig {
+    fn default() -> Self {
+        AssistConfig { snippet_cap: Some(SnippetCap { _private: () }) }
+    }
+}
diff --git a/crates/ra_assists/src/assist_context.rs b/crates/ra_assists/src/assist_context.rs
index a680f752b..0dcd9df61 100644
--- a/crates/ra_assists/src/assist_context.rs
+++ b/crates/ra_assists/src/assist_context.rs
@@ -15,7 +15,10 @@ use ra_syntax::{
 };
 use ra_text_edit::TextEditBuilder;
 
-use crate::{Assist, AssistId, GroupLabel, ResolvedAssist};
+use crate::{
+    assist_config::{AssistConfig, SnippetCap},
+    Assist, AssistId, GroupLabel, ResolvedAssist,
+};
 
 /// `AssistContext` allows to apply an assist or check if it could be applied.
 ///
@@ -48,6 +51,7 @@ use crate::{Assist, AssistId, GroupLabel, ResolvedAssist};
 /// moment, because the LSP API is pretty awkward in this place, and it's much
 /// easier to just compute the edit eagerly :-)
 pub(crate) struct AssistContext<'a> {
+    pub(crate) config: &'a AssistConfig,
     pub(crate) sema: Semantics<'a, RootDatabase>,
     pub(crate) db: &'a RootDatabase,
     pub(crate) frange: FileRange,
@@ -55,10 +59,14 @@ pub(crate) struct AssistContext<'a> {
 }
 
 impl<'a> AssistContext<'a> {
-    pub fn new(sema: Semantics<'a, RootDatabase>, frange: FileRange) -> AssistContext<'a> {
+    pub(crate) fn new(
+        sema: Semantics<'a, RootDatabase>,
+        config: &'a AssistConfig,
+        frange: FileRange,
+    ) -> AssistContext<'a> {
         let source_file = sema.parse(frange.file_id);
         let db = sema.db;
-        AssistContext { sema, db, frange, source_file }
+        AssistContext { config, sema, db, frange, source_file }
     }
 
     // NB, this ignores active selection.
@@ -165,11 +173,17 @@ pub(crate) struct AssistBuilder {
     edit: TextEditBuilder,
     cursor_position: Option<TextSize>,
     file: FileId,
+    is_snippet: bool,
 }
 
 impl AssistBuilder {
     pub(crate) fn new(file: FileId) -> AssistBuilder {
-        AssistBuilder { edit: TextEditBuilder::default(), cursor_position: None, file }
+        AssistBuilder {
+            edit: TextEditBuilder::default(),
+            cursor_position: None,
+            file,
+            is_snippet: false,
+        }
     }
 
     /// Remove specified `range` of text.
@@ -180,6 +194,16 @@ impl AssistBuilder {
     pub(crate) fn insert(&mut self, offset: TextSize, text: impl Into<String>) {
         self.edit.insert(offset, text.into())
     }
+    /// Append specified `text` at the given `offset`
+    pub(crate) fn insert_snippet(
+        &mut self,
+        _cap: SnippetCap,
+        offset: TextSize,
+        text: impl Into<String>,
+    ) {
+        self.is_snippet = true;
+        self.edit.insert(offset, text.into())
+    }
     /// Replaces specified `range` of text with a given string.
     pub(crate) fn replace(&mut self, range: TextRange, replace_with: impl Into<String>) {
         self.edit.replace(range, replace_with.into())
@@ -227,7 +251,12 @@ impl AssistBuilder {
         if edit.is_empty() && self.cursor_position.is_none() {
             panic!("Only call `add_assist` if the assist can be applied")
         }
-        SingleFileChange { label: change_label, edit, cursor_position: self.cursor_position }
-            .into_source_change(self.file)
+        let mut res =
+            SingleFileChange { label: change_label, edit, cursor_position: self.cursor_position }
+                .into_source_change(self.file);
+        if self.is_snippet {
+            res.is_snippet = true;
+        }
+        res
     }
 }
diff --git a/crates/ra_assists/src/handlers/add_custom_impl.rs b/crates/ra_assists/src/handlers/add_custom_impl.rs
index 2baeb8607..fa70c8496 100644
--- a/crates/ra_assists/src/handlers/add_custom_impl.rs
+++ b/crates/ra_assists/src/handlers/add_custom_impl.rs
@@ -25,7 +25,7 @@ use crate::{
 // struct S;
 //
 // impl Debug for S {
-//
+//     $0
 // }
 // ```
 pub(crate) fn add_custom_impl(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
@@ -52,7 +52,7 @@ pub(crate) fn add_custom_impl(acc: &mut Assists, ctx: &AssistContext) -> Option<
         format!("Add custom impl `{}` for `{}`", trait_token.text().as_str(), annotated_name);
 
     let target = attr.syntax().text_range();
-    acc.add(AssistId("add_custom_impl"), label, target, |edit| {
+    acc.add(AssistId("add_custom_impl"), label, target, |builder| {
         let new_attr_input = input
             .syntax()
             .descendants_with_tokens()
@@ -63,20 +63,11 @@ pub(crate) fn add_custom_impl(acc: &mut Assists, ctx: &AssistContext) -> Option<
         let has_more_derives = !new_attr_input.is_empty();
         let new_attr_input = new_attr_input.iter().sep_by(", ").surround_with("(", ")").to_string();
 
-        let mut buf = String::new();
-        buf.push_str("\n\nimpl ");
-        buf.push_str(trait_token.text().as_str());
-        buf.push_str(" for ");
-        buf.push_str(annotated_name.as_str());
-        buf.push_str(" {\n");
-
-        let cursor_delta = if has_more_derives {
-            let delta = input.syntax().text_range().len() - TextSize::of(&new_attr_input);
-            edit.replace(input.syntax().text_range(), new_attr_input);
-            delta
+        if has_more_derives {
+            builder.replace(input.syntax().text_range(), new_attr_input);
         } else {
             let attr_range = attr.syntax().text_range();
-            edit.delete(attr_range);
+            builder.delete(attr_range);
 
             let line_break_range = attr
                 .syntax()
@@ -84,14 +75,24 @@ pub(crate) fn add_custom_impl(acc: &mut Assists, ctx: &AssistContext) -> Option<
                 .filter(|t| t.kind() == WHITESPACE)
                 .map(|t| t.text_range())
                 .unwrap_or_else(|| TextRange::new(TextSize::from(0), TextSize::from(0)));
-            edit.delete(line_break_range);
-
-            attr_range.len() + line_break_range.len()
-        };
-
-        edit.set_cursor(start_offset + TextSize::of(&buf) - cursor_delta);
-        buf.push_str("\n}");
-        edit.insert(start_offset, buf);
+            builder.delete(line_break_range);
+        }
+
+        match ctx.config.snippet_cap {
+            Some(cap) => {
+                builder.insert_snippet(
+                    cap,
+                    start_offset,
+                    format!("\n\nimpl {} for {} {{\n    $0\n}}", trait_token, annotated_name),
+                );
+            }
+            None => {
+                builder.insert(
+                    start_offset,
+                    format!("\n\nimpl {} for {} {{\n\n}}", trait_token, annotated_name),
+                );
+            }
+        }
     })
 }
 
@@ -117,7 +118,7 @@ struct Foo {
 }
 
 impl Debug for Foo {
-<|>
+    $0
 }
             ",
         )
@@ -139,7 +140,7 @@ pub struct Foo {
 }
 
 impl Debug for Foo {
-<|>
+    $0
 }
             ",
         )
@@ -158,7 +159,7 @@ struct Foo {}
 struct Foo {}
 
 impl Debug for Foo {
-<|>
+    $0
 }
             ",
         )
diff --git a/crates/ra_assists/src/handlers/add_derive.rs b/crates/ra_assists/src/handlers/add_derive.rs
index fb08c19e9..b123b8498 100644
--- a/crates/ra_assists/src/handlers/add_derive.rs
+++ b/crates/ra_assists/src/handlers/add_derive.rs
@@ -18,31 +18,37 @@ use crate::{AssistContext, AssistId, Assists};
 // ```
 // ->
 // ```
-// #[derive()]
+// #[derive($0)]
 // struct Point {
 //     x: u32,
 //     y: u32,
 // }
 // ```
 pub(crate) fn add_derive(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
+    let cap = ctx.config.snippet_cap?;
     let nominal = ctx.find_node_at_offset::<ast::NominalDef>()?;
     let node_start = derive_insertion_offset(&nominal)?;
     let target = nominal.syntax().text_range();
-    acc.add(AssistId("add_derive"), "Add `#[derive]`", target, |edit| {
+    acc.add(AssistId("add_derive"), "Add `#[derive]`", target, |builder| {
         let derive_attr = nominal
             .attrs()
             .filter_map(|x| x.as_simple_call())
             .filter(|(name, _arg)| name == "derive")
             .map(|(_name, arg)| arg)
             .next();
-        let offset = match derive_attr {
+        match derive_attr {
             None => {
-                edit.insert(node_start, "#[derive()]\n");
-                node_start + TextSize::of("#[derive(")
+                builder.insert_snippet(cap, node_start, "#[derive($0)]\n");
+            }
+            Some(tt) => {
+                // Just move the cursor.
+                builder.insert_snippet(
+                    cap,
+                    tt.syntax().text_range().end() - TextSize::of(')'),
+                    "$0",
+                )
             }
-            Some(tt) => tt.syntax().text_range().end() - TextSize::of(')'),
         };
-        edit.set_cursor(offset)
     })
 }
 
@@ -66,12 +72,12 @@ mod tests {
         check_assist(
             add_derive,
             "struct Foo { a: i32, <|>}",
-            "#[derive(<|>)]\nstruct Foo { a: i32, }",
+            "#[derive($0)]\nstruct Foo { a: i32, }",
         );
         check_assist(
             add_derive,
             "struct Foo { <|> a: i32, }",
-            "#[derive(<|>)]\nstruct Foo {  a: i32, }",
+            "#[derive($0)]\nstruct Foo {  a: i32, }",
         );
     }
 
@@ -80,7 +86,7 @@ mod tests {
         check_assist(
             add_derive,
             "#[derive(Clone)]\nstruct Foo { a: i32<|>, }",
-            "#[derive(Clone<|>)]\nstruct Foo { a: i32, }",
+            "#[derive(Clone$0)]\nstruct Foo { a: i32, }",
         );
     }
 
@@ -96,7 +102,7 @@ struct Foo { a: i32<|>, }
             "
 /// `Foo` is a pretty important struct.
 /// It does stuff.
-#[derive(<|>)]
+#[derive($0)]
 struct Foo { a: i32, }
             ",
         );
diff --git a/crates/ra_assists/src/handlers/add_impl.rs b/crates/ra_assists/src/handlers/add_impl.rs
index df114a0d8..eceba7d0a 100644
--- a/crates/ra_assists/src/handlers/add_impl.rs
+++ b/crates/ra_assists/src/handlers/add_impl.rs
@@ -1,7 +1,4 @@
-use ra_syntax::{
-    ast::{self, AstNode, NameOwner, TypeParamsOwner},
-    TextSize,
-};
+use ra_syntax::ast::{self, AstNode, NameOwner, TypeParamsOwner};
 use stdx::{format_to, SepBy};
 
 use crate::{AssistContext, AssistId, Assists};
@@ -12,17 +9,17 @@ use crate::{AssistContext, AssistId, Assists};
 //
 // ```
 // struct Ctx<T: Clone> {
-//      data: T,<|>
+//     data: T,<|>
 // }
 // ```
 // ->
 // ```
 // struct Ctx<T: Clone> {
-//      data: T,
+//     data: T,
 // }
 //
 // impl<T: Clone> Ctx<T> {
-//
+//     $0
 // }
 // ```
 pub(crate) fn add_impl(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
@@ -50,30 +47,37 @@ pub(crate) fn add_impl(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
             let generic_params = lifetime_params.chain(type_params).sep_by(", ");
             format_to!(buf, "<{}>", generic_params)
         }
-        buf.push_str(" {\n");
-        edit.set_cursor(start_offset + TextSize::of(&buf));
-        buf.push_str("\n}");
-        edit.insert(start_offset, buf);
+        match ctx.config.snippet_cap {
+            Some(cap) => {
+                buf.push_str(" {\n    $0\n}");
+                edit.insert_snippet(cap, start_offset, buf);
+            }
+            None => {
+                buf.push_str(" {\n}");
+                edit.insert(start_offset, buf);
+            }
+        }
     })
 }
 
 #[cfg(test)]
 mod tests {
-    use super::*;
     use crate::tests::{check_assist, check_assist_target};
 
+    use super::*;
+
     #[test]
     fn test_add_impl() {
-        check_assist(add_impl, "struct Foo {<|>}\n", "struct Foo {}\n\nimpl Foo {\n<|>\n}\n");
+        check_assist(add_impl, "struct Foo {<|>}\n", "struct Foo {}\n\nimpl Foo {\n    $0\n}\n");
         check_assist(
             add_impl,
             "struct Foo<T: Clone> {<|>}",
-            "struct Foo<T: Clone> {}\n\nimpl<T: Clone> Foo<T> {\n<|>\n}",
+            "struct Foo<T: Clone> {}\n\nimpl<T: Clone> Foo<T> {\n    $0\n}",
         );
         check_assist(
             add_impl,
             "struct Foo<'a, T: Foo<'a>> {<|>}",
-            "struct Foo<'a, T: Foo<'a>> {}\n\nimpl<'a, T: Foo<'a>> Foo<'a, T> {\n<|>\n}",
+            "struct Foo<'a, T: Foo<'a>> {}\n\nimpl<'a, T: Foo<'a>> Foo<'a, T> {\n    $0\n}",
         );
     }
 
diff --git a/crates/ra_assists/src/lib.rs b/crates/ra_assists/src/lib.rs
index b6dc7cb1b..7f0a723c9 100644
--- a/crates/ra_assists/src/lib.rs
+++ b/crates/ra_assists/src/lib.rs
@@ -10,6 +10,7 @@ macro_rules! eprintln {
     ($($tt:tt)*) => { stdx::eprintln!($($tt)*) };
 }
 
+mod assist_config;
 mod assist_context;
 mod marks;
 #[cfg(test)]
@@ -24,6 +25,8 @@ use ra_syntax::TextRange;
 
 pub(crate) use crate::assist_context::{AssistContext, Assists};
 
+pub use assist_config::AssistConfig;
+
 /// Unique identifier of the assist, should not be shown to the user
 /// directly.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -54,9 +57,9 @@ impl Assist {
     ///
     /// Assists are returned in the "unresolved" state, that is only labels are
     /// returned, without actual edits.
-    pub fn unresolved(db: &RootDatabase, range: FileRange) -> Vec<Assist> {
+    pub fn unresolved(db: &RootDatabase, config: &AssistConfig, range: FileRange) -> Vec<Assist> {
         let sema = Semantics::new(db);
-        let ctx = AssistContext::new(sema, range);
+        let ctx = AssistContext::new(sema, config, range);
         let mut acc = Assists::new_unresolved(&ctx);
         handlers::all().iter().for_each(|handler| {
             handler(&mut acc, &ctx);
@@ -68,9 +71,13 @@ impl Assist {
     ///
     /// Assists are returned in the "resolved" state, that is with edit fully
     /// computed.
-    pub fn resolved(db: &RootDatabase, range: FileRange) -> Vec<ResolvedAssist> {
+    pub fn resolved(
+        db: &RootDatabase,
+        config: &AssistConfig,
+        range: FileRange,
+    ) -> Vec<ResolvedAssist> {
         let sema = Semantics::new(db);
-        let ctx = AssistContext::new(sema, range);
+        let ctx = AssistContext::new(sema, config, range);
         let mut acc = Assists::new_resolved(&ctx);
         handlers::all().iter().for_each(|handler| {
             handler(&mut acc, &ctx);
diff --git a/crates/ra_assists/src/tests.rs b/crates/ra_assists/src/tests.rs
index a3eacb8f1..9ba3da786 100644
--- a/crates/ra_assists/src/tests.rs
+++ b/crates/ra_assists/src/tests.rs
@@ -11,7 +11,7 @@ use test_utils::{
     RangeOrOffset,
 };
 
-use crate::{handlers::Handler, Assist, AssistContext, Assists};
+use crate::{handlers::Handler, Assist, AssistConfig, AssistContext, Assists};
 
 pub(crate) fn with_single_file(text: &str) -> (RootDatabase, FileId) {
     let (mut db, file_id) = RootDatabase::with_single_file(text);
@@ -41,14 +41,14 @@ fn check_doc_test(assist_id: &str, before: &str, after: &str) {
     let (db, file_id) = crate::tests::with_single_file(&before);
     let frange = FileRange { file_id, range: selection.into() };
 
-    let mut assist = Assist::resolved(&db, frange)
+    let mut assist = Assist::resolved(&db, &AssistConfig::default(), frange)
         .into_iter()
         .find(|assist| assist.assist.id.0 == assist_id)
         .unwrap_or_else(|| {
             panic!(
                 "\n\nAssist is not applicable: {}\nAvailable assists: {}",
                 assist_id,
-                Assist::resolved(&db, frange)
+                Assist::resolved(&db, &AssistConfig::default(), frange)
                     .into_iter()
                     .map(|assist| assist.assist.id.0)
                     .collect::<Vec<_>>()
@@ -90,7 +90,8 @@ fn check(handler: Handler, before: &str, expected: ExpectedResult) {
     let frange = FileRange { file_id: file_with_caret_id, range: range_or_offset.into() };
 
     let sema = Semantics::new(&db);
-    let ctx = AssistContext::new(sema, frange);
+    let config = AssistConfig::default();
+    let ctx = AssistContext::new(sema, &config, frange);
     let mut acc = Assists::new_resolved(&ctx);
     handler(&mut acc, &ctx);
     let mut res = acc.finish_resolved();
@@ -103,19 +104,20 @@ fn check(handler: Handler, before: &str, expected: ExpectedResult) {
             let mut actual = db.file_text(change.file_id).as_ref().to_owned();
             change.edit.apply(&mut actual);
 
-            match source_change.cursor_position {
-                None => {
-                    if let RangeOrOffset::Offset(before_cursor_pos) = range_or_offset {
-                        let off = change
-                            .edit
-                            .apply_to_offset(before_cursor_pos)
-                            .expect("cursor position is affected by the edit");
-                        actual = add_cursor(&actual, off)
+            if !source_change.is_snippet {
+                match source_change.cursor_position {
+                    None => {
+                        if let RangeOrOffset::Offset(before_cursor_pos) = range_or_offset {
+                            let off = change
+                                .edit
+                                .apply_to_offset(before_cursor_pos)
+                                .expect("cursor position is affected by the edit");
+                            actual = add_cursor(&actual, off)
+                        }
                     }
-                }
-                Some(off) => actual = add_cursor(&actual, off.offset),
-            };
-
+                    Some(off) => actual = add_cursor(&actual, off.offset),
+                };
+            }
             assert_eq_text!(after, &actual);
         }
         (Some(assist), ExpectedResult::Target(target)) => {
@@ -136,7 +138,7 @@ fn assist_order_field_struct() {
     let (before_cursor_pos, before) = extract_offset(before);
     let (db, file_id) = with_single_file(&before);
     let frange = FileRange { file_id, range: TextRange::empty(before_cursor_pos) };
-    let assists = Assist::resolved(&db, frange);
+    let assists = Assist::resolved(&db, &AssistConfig::default(), frange);
     let mut assists = assists.iter();
 
     assert_eq!(
@@ -159,7 +161,7 @@ fn assist_order_if_expr() {
     let (range, before) = extract_range(before);
     let (db, file_id) = with_single_file(&before);
     let frange = FileRange { file_id, range };
-    let assists = Assist::resolved(&db, frange);
+    let assists = Assist::resolved(&db, &AssistConfig::default(), frange);
     let mut assists = assists.iter();
 
     assert_eq!(assists.next().expect("expected assist").assist.label, "Extract into variable");
diff --git a/crates/ra_assists/src/tests/generated.rs b/crates/ra_assists/src/tests/generated.rs
index 972dbd251..9487c9239 100644
--- a/crates/ra_assists/src/tests/generated.rs
+++ b/crates/ra_assists/src/tests/generated.rs
@@ -15,7 +15,7 @@ struct S;
 struct S;
 
 impl Debug for S {
-
+    $0
 }
 "#####,
     )
@@ -32,7 +32,7 @@ struct Point {
 }
 "#####,
         r#####"
-#[derive()]
+#[derive($0)]
 struct Point {
     x: u32,
     y: u32,
@@ -108,16 +108,16 @@ fn doctest_add_impl() {
         "add_impl",
         r#####"
 struct Ctx<T: Clone> {
-     data: T,<|>
+    data: T,<|>
 }
 "#####,
         r#####"
 struct Ctx<T: Clone> {
-     data: T,
+    data: T,
 }
 
 impl<T: Clone> Ctx<T> {
-
+    $0
 }
 "#####,
     )
diff --git a/crates/ra_ide/src/completion.rs b/crates/ra_ide/src/completion.rs
index 8bdc43b1a..191300704 100644
--- a/crates/ra_ide/src/completion.rs
+++ b/crates/ra_ide/src/completion.rs
@@ -59,8 +59,8 @@ pub use crate::completion::{
 /// with ordering of completions (currently this is done by the client).
 pub(crate) fn completions(
     db: &RootDatabase,
-    position: FilePosition,
     config: &CompletionConfig,
+    position: FilePosition,
 ) -> Option<Completions> {
     let ctx = CompletionContext::new(db, position, config)?;
 
diff --git a/crates/ra_ide/src/completion/test_utils.rs b/crates/ra_ide/src/completion/test_utils.rs
index eb90b5279..bf22452a2 100644
--- a/crates/ra_ide/src/completion/test_utils.rs
+++ b/crates/ra_ide/src/completion/test_utils.rs
@@ -20,7 +20,7 @@ pub(crate) fn do_completion_with_options(
     } else {
         single_file_with_position(code)
     };
-    let completions = analysis.completions(position, options).unwrap().unwrap();
+    let completions = analysis.completions(options, position).unwrap().unwrap();
     let completion_items: Vec<CompletionItem> = completions.into();
     let mut kind_completions: Vec<CompletionItem> =
         completion_items.into_iter().filter(|c| c.completion_kind == kind).collect();
diff --git a/crates/ra_ide/src/diagnostics.rs b/crates/ra_ide/src/diagnostics.rs
index 87a0b80f1..54c2bcc09 100644
--- a/crates/ra_ide/src/diagnostics.rs
+++ b/crates/ra_ide/src/diagnostics.rs
@@ -629,6 +629,7 @@ mod tests {
                             },
                         ],
                         cursor_position: None,
+                        is_snippet: false,
                     },
                 ),
                 severity: Error,
@@ -685,6 +686,7 @@ mod tests {
                         ],
                         file_system_edits: [],
                         cursor_position: None,
+                        is_snippet: false,
                     },
                 ),
                 severity: Error,
diff --git a/crates/ra_ide/src/lib.rs b/crates/ra_ide/src/lib.rs
index 78149ddfc..66125f2f5 100644
--- a/crates/ra_ide/src/lib.rs
+++ b/crates/ra_ide/src/lib.rs
@@ -82,7 +82,7 @@ pub use crate::{
 };
 
 pub use hir::Documentation;
-pub use ra_assists::AssistId;
+pub use ra_assists::{AssistConfig, AssistId};
 pub use ra_db::{
     Canceled, CrateGraph, CrateId, Edition, FileId, FilePosition, FileRange, SourceRootId,
 };
@@ -458,17 +458,17 @@ impl Analysis {
     /// Computes completions at the given position.
     pub fn completions(
         &self,
-        position: FilePosition,
         config: &CompletionConfig,
+        position: FilePosition,
     ) -> Cancelable<Option<Vec<CompletionItem>>> {
-        self.with_db(|db| completion::completions(db, position, config).map(Into::into))
+        self.with_db(|db| completion::completions(db, config, position).map(Into::into))
     }
 
     /// Computes assists (aka code actions aka intentions) for the given
     /// position.
-    pub fn assists(&self, frange: FileRange) -> Cancelable<Vec<Assist>> {
+    pub fn assists(&self, config: &AssistConfig, frange: FileRange) -> Cancelable<Vec<Assist>> {
         self.with_db(|db| {
-            ra_assists::Assist::resolved(db, frange)
+            ra_assists::Assist::resolved(db, config, frange)
                 .into_iter()
                 .map(|assist| Assist {
                     id: assist.assist.id,
diff --git a/crates/ra_ide/src/references/rename.rs b/crates/ra_ide/src/references/rename.rs
index 410dae75c..68a53ad4b 100644
--- a/crates/ra_ide/src/references/rename.rs
+++ b/crates/ra_ide/src/references/rename.rs
@@ -670,6 +670,7 @@ mod tests {
                         },
                     ],
                     cursor_position: None,
+                    is_snippet: false,
                 },
             },
         )
@@ -722,6 +723,7 @@ mod tests {
                         },
                     ],
                     cursor_position: None,
+                    is_snippet: false,
                 },
             },
         )
@@ -818,6 +820,7 @@ mod tests {
                         },
                     ],
                     cursor_position: None,
+                    is_snippet: false,
                 },
             },
         )
diff --git a/crates/ra_ide_db/src/source_change.rs b/crates/ra_ide_db/src/source_change.rs
index af81a91a4..c64165f3a 100644
--- a/crates/ra_ide_db/src/source_change.rs
+++ b/crates/ra_ide_db/src/source_change.rs
@@ -13,6 +13,7 @@ pub struct SourceChange {
     pub source_file_edits: Vec<SourceFileEdit>,
     pub file_system_edits: Vec<FileSystemEdit>,
     pub cursor_position: Option<FilePosition>,
+    pub is_snippet: bool,
 }
 
 impl SourceChange {
@@ -28,6 +29,7 @@ impl SourceChange {
             source_file_edits,
             file_system_edits,
             cursor_position: None,
+            is_snippet: false,
         }
     }
 
@@ -41,6 +43,7 @@ impl SourceChange {
             source_file_edits: edits,
             file_system_edits: vec![],
             cursor_position: None,
+            is_snippet: false,
         }
     }
 
@@ -52,6 +55,7 @@ impl SourceChange {
             source_file_edits: vec![],
             file_system_edits: edits,
             cursor_position: None,
+            is_snippet: false,
         }
     }
 
@@ -115,6 +119,7 @@ impl SingleFileChange {
             source_file_edits: vec![SourceFileEdit { file_id, edit: self.edit }],
             file_system_edits: Vec::new(),
             cursor_position: self.cursor_position.map(|offset| FilePosition { file_id, offset }),
+            is_snippet: false,
         }
     }
 }
diff --git a/crates/rust-analyzer/src/cli/analysis_bench.rs b/crates/rust-analyzer/src/cli/analysis_bench.rs
index 6147ae207..b20efe98d 100644
--- a/crates/rust-analyzer/src/cli/analysis_bench.rs
+++ b/crates/rust-analyzer/src/cli/analysis_bench.rs
@@ -105,7 +105,7 @@ pub fn analysis_bench(
             if is_completion {
                 let options = CompletionConfig::default();
                 let res = do_work(&mut host, file_id, |analysis| {
-                    analysis.completions(file_position, &options)
+                    analysis.completions(&options, file_position)
                 });
                 if verbosity.is_verbose() {
                     println!("\n{:#?}", res);
diff --git a/crates/rust-analyzer/src/config.rs b/crates/rust-analyzer/src/config.rs
index b5dc6f0fa..d75c48597 100644
--- a/crates/rust-analyzer/src/config.rs
+++ b/crates/rust-analyzer/src/config.rs
@@ -11,7 +11,7 @@ use std::{ffi::OsString, path::PathBuf};
 
 use lsp_types::ClientCapabilities;
 use ra_flycheck::FlycheckConfig;
-use ra_ide::{CompletionConfig, InlayHintsConfig};
+use ra_ide::{AssistConfig, CompletionConfig, InlayHintsConfig};
 use ra_project_model::CargoConfig;
 use serde::Deserialize;
 
@@ -32,6 +32,7 @@ pub struct Config {
 
     pub inlay_hints: InlayHintsConfig,
     pub completion: CompletionConfig,
+    pub assist: AssistConfig,
     pub call_info_full: bool,
     pub lens: LensConfig,
 }
@@ -136,6 +137,7 @@ impl Default for Config {
                 add_call_argument_snippets: true,
                 ..CompletionConfig::default()
             },
+            assist: AssistConfig::default(),
             call_info_full: true,
             lens: LensConfig::default(),
         }
@@ -273,6 +275,7 @@ impl Config {
             {
                 self.client_caps.code_action_literals = value;
             }
+
             self.completion.allow_snippets(false);
             if let Some(completion) = &doc_caps.completion {
                 if let Some(completion_item) = &completion.completion_item {
@@ -288,5 +291,12 @@ impl Config {
                 self.client_caps.work_done_progress = value;
             }
         }
+
+        self.assist.allow_snippets(false);
+        if let Some(experimental) = &caps.experimental {
+            let enable =
+                experimental.get("snippetTextEdit").and_then(|it| it.as_bool()) == Some(true);
+            self.assist.allow_snippets(enable);
+        }
     }
 }
diff --git a/crates/rust-analyzer/src/diagnostics.rs b/crates/rust-analyzer/src/diagnostics.rs
index 4bdd45a7d..25856c543 100644
--- a/crates/rust-analyzer/src/diagnostics.rs
+++ b/crates/rust-analyzer/src/diagnostics.rs
@@ -3,9 +3,11 @@ pub(crate) mod to_proto;
 
 use std::{collections::HashMap, sync::Arc};
 
-use lsp_types::{CodeActionOrCommand, Diagnostic, Range};
+use lsp_types::{Diagnostic, Range};
 use ra_ide::FileId;
 
+use crate::lsp_ext;
+
 pub type CheckFixes = Arc<HashMap<FileId, Vec<Fix>>>;
 
 #[derive(Debug, Default, Clone)]
@@ -18,13 +20,13 @@ pub struct DiagnosticCollection {
 #[derive(Debug, Clone)]
 pub struct Fix {
     pub range: Range,
-    pub action: CodeActionOrCommand,
+    pub action: lsp_ext::CodeAction,
 }
 
 #[derive(Debug)]
 pub enum DiagnosticTask {
     ClearCheck,
-    AddCheck(FileId, Diagnostic, Vec<CodeActionOrCommand>),
+    AddCheck(FileId, Diagnostic, Vec<lsp_ext::CodeAction>),
     SetNative(FileId, Vec<Diagnostic>),
 }
 
@@ -38,7 +40,7 @@ impl DiagnosticCollection {
         &mut self,
         file_id: FileId,
         diagnostic: Diagnostic,
-        fixes: Vec<CodeActionOrCommand>,
+        fixes: Vec<lsp_ext::CodeAction>,
     ) {
         let diagnostics = self.check.entry(file_id).or_default();
         for existing_diagnostic in diagnostics.iter() {
diff --git a/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_multi_line_fix.snap b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_multi_line_fix.snap
index 076b3cf27..96466b5c9 100644
--- a/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_multi_line_fix.snap
+++ b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_multi_line_fix.snap
@@ -68,9 +68,9 @@ expression: diag
                 kind: Some(
                     "quickfix",
                 ),
-                diagnostics: None,
+                command: None,
                 edit: Some(
-                    WorkspaceEdit {
+                    SnippetWorkspaceEdit {
                         changes: Some(
                             {
                                 "file:///test/src/main.rs": [
@@ -106,8 +106,6 @@ expression: diag
                         document_changes: None,
                     },
                 ),
-                command: None,
-                is_preferred: None,
             },
         ],
     },
diff --git a/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_rustc_unused_variable.snap b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_rustc_unused_variable.snap
index 69138c15b..8f962277f 100644
--- a/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_rustc_unused_variable.snap
+++ b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_rustc_unused_variable.snap
@@ -53,9 +53,9 @@ expression: diag
                 kind: Some(
                     "quickfix",
                 ),
-                diagnostics: None,
+                command: None,
                 edit: Some(
-                    WorkspaceEdit {
+                    SnippetWorkspaceEdit {
                         changes: Some(
                             {
                                 "file:///test/driver/subcommand/repl.rs": [
@@ -78,8 +78,6 @@ expression: diag
                         document_changes: None,
                     },
                 ),
-                command: None,
-                is_preferred: None,
             },
         ],
     },
diff --git a/crates/rust-analyzer/src/diagnostics/to_proto.rs b/crates/rust-analyzer/src/diagnostics/to_proto.rs
index eabf4908f..afea59525 100644
--- a/crates/rust-analyzer/src/diagnostics/to_proto.rs
+++ b/crates/rust-analyzer/src/diagnostics/to_proto.rs
@@ -7,13 +7,13 @@ use std::{
 };
 
 use lsp_types::{
-    CodeAction, Diagnostic, DiagnosticRelatedInformation, DiagnosticSeverity, DiagnosticTag,
-    Location, NumberOrString, Position, Range, TextEdit, Url, WorkspaceEdit,
+    Diagnostic, DiagnosticRelatedInformation, DiagnosticSeverity, DiagnosticTag, Location,
+    NumberOrString, Position, Range, TextEdit, Url,
 };
 use ra_flycheck::{Applicability, DiagnosticLevel, DiagnosticSpan, DiagnosticSpanMacroExpansion};
 use stdx::format_to;
 
-use crate::Result;
+use crate::{lsp_ext, Result};
 
 /// Converts a Rust level string to a LSP severity
 fn map_level_to_severity(val: DiagnosticLevel) -> Option<DiagnosticSeverity> {
@@ -110,7 +110,7 @@ fn is_deprecated(rd: &ra_flycheck::Diagnostic) -> bool {
 
 enum MappedRustChildDiagnostic {
     Related(DiagnosticRelatedInformation),
-    SuggestedFix(CodeAction),
+    SuggestedFix(lsp_ext::CodeAction),
     MessageLine(String),
 }
 
@@ -143,13 +143,15 @@ fn map_rust_child_diagnostic(
             message: rd.message.clone(),
         })
     } else {
-        MappedRustChildDiagnostic::SuggestedFix(CodeAction {
+        MappedRustChildDiagnostic::SuggestedFix(lsp_ext::CodeAction {
             title: rd.message.clone(),
             kind: Some("quickfix".to_string()),
-            diagnostics: None,
-            edit: Some(WorkspaceEdit::new(edit_map)),
+            edit: Some(lsp_ext::SnippetWorkspaceEdit {
+                // FIXME: there's no good reason to use edit_map here....
+                changes: Some(edit_map),
+                document_changes: None,
+            }),
             command: None,
-            is_preferred: None,
         })
     }
 }
@@ -158,7 +160,7 @@ fn map_rust_child_diagnostic(
 pub(crate) struct MappedRustDiagnostic {
     pub location: Location,
     pub diagnostic: Diagnostic,
-    pub fixes: Vec<CodeAction>,
+    pub fixes: Vec<lsp_ext::CodeAction>,
 }
 
 /// Converts a Rust root diagnostic to LSP form
diff --git a/crates/rust-analyzer/src/lsp_ext.rs b/crates/rust-analyzer/src/lsp_ext.rs
index 313a8c769..f75a26eb7 100644
--- a/crates/rust-analyzer/src/lsp_ext.rs
+++ b/crates/rust-analyzer/src/lsp_ext.rs
@@ -1,6 +1,6 @@
 //! rust-analyzer extensions to the LSP.
 
-use std::path::PathBuf;
+use std::{collections::HashMap, path::PathBuf};
 
 use lsp_types::request::Request;
 use lsp_types::{Location, Position, Range, TextDocumentIdentifier};
@@ -137,7 +137,7 @@ pub struct Runnable {
 #[serde(rename_all = "camelCase")]
 pub struct SourceChange {
     pub label: String,
-    pub workspace_edit: lsp_types::WorkspaceEdit,
+    pub workspace_edit: SnippetWorkspaceEdit,
     pub cursor_position: Option<lsp_types::TextDocumentPositionParams>,
 }
 
@@ -183,3 +183,54 @@ pub struct SsrParams {
     pub query: String,
     pub parse_only: bool,
 }
+
+pub enum CodeActionRequest {}
+
+impl Request for CodeActionRequest {
+    type Params = lsp_types::CodeActionParams;
+    type Result = Option<Vec<CodeAction>>;
+    const METHOD: &'static str = "textDocument/codeAction";
+}
+
+#[derive(Debug, PartialEq, Clone, Default, Deserialize, Serialize)]
+pub struct CodeAction {
+    pub title: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub kind: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub command: Option<lsp_types::Command>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub edit: Option<SnippetWorkspaceEdit>,
+}
+
+#[derive(Debug, Eq, PartialEq, Clone, Default, Deserialize, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct SnippetWorkspaceEdit {
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub changes: Option<HashMap<lsp_types::Url, Vec<lsp_types::TextEdit>>>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub document_changes: Option<Vec<SnippetDocumentChangeOperation>>,
+}
+
+#[derive(Debug, Eq, PartialEq, Clone, Deserialize, Serialize)]
+#[serde(untagged, rename_all = "lowercase")]
+pub enum SnippetDocumentChangeOperation {
+    Op(lsp_types::ResourceOp),
+    Edit(SnippetTextDocumentEdit),
+}
+
+#[derive(Debug, Eq, PartialEq, Clone, Deserialize, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct SnippetTextDocumentEdit {
+    pub text_document: lsp_types::VersionedTextDocumentIdentifier,
+    pub edits: Vec<SnippetTextEdit>,
+}
+
+#[derive(Debug, Eq, PartialEq, Clone, Default, Deserialize, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct SnippetTextEdit {
+    pub range: Range,
+    pub new_text: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub insert_text_format: Option<lsp_types::InsertTextFormat>,
+}
diff --git a/crates/rust-analyzer/src/main_loop.rs b/crates/rust-analyzer/src/main_loop.rs
index 15e5bb354..87795fffb 100644
--- a/crates/rust-analyzer/src/main_loop.rs
+++ b/crates/rust-analyzer/src/main_loop.rs
@@ -518,6 +518,7 @@ fn on_request(
         .on::<lsp_ext::ParentModule>(handlers::handle_parent_module)?
         .on::<lsp_ext::Runnables>(handlers::handle_runnables)?
         .on::<lsp_ext::InlayHints>(handlers::handle_inlay_hints)?
+        .on::<lsp_ext::CodeActionRequest>(handlers::handle_code_action)?
         .on::<lsp_types::request::OnTypeFormatting>(handlers::handle_on_type_formatting)?
         .on::<lsp_types::request::DocumentSymbolRequest>(handlers::handle_document_symbol)?
         .on::<lsp_types::request::WorkspaceSymbol>(handlers::handle_workspace_symbol)?
@@ -525,7 +526,6 @@ fn on_request(
         .on::<lsp_types::request::GotoImplementation>(handlers::handle_goto_implementation)?
         .on::<lsp_types::request::GotoTypeDefinition>(handlers::handle_goto_type_definition)?
         .on::<lsp_types::request::Completion>(handlers::handle_completion)?
-        .on::<lsp_types::request::CodeActionRequest>(handlers::handle_code_action)?
         .on::<lsp_types::request::CodeLensRequest>(handlers::handle_code_lens)?
         .on::<lsp_types::request::CodeLensResolve>(handlers::handle_code_lens_resolve)?
         .on::<lsp_types::request::FoldingRangeRequest>(handlers::handle_folding_range)?
diff --git a/crates/rust-analyzer/src/main_loop/handlers.rs b/crates/rust-analyzer/src/main_loop/handlers.rs
index e67556752..4ff8fa69e 100644
--- a/crates/rust-analyzer/src/main_loop/handlers.rs
+++ b/crates/rust-analyzer/src/main_loop/handlers.rs
@@ -11,12 +11,11 @@ use lsp_server::ErrorCode;
 use lsp_types::{
     CallHierarchyIncomingCall, CallHierarchyIncomingCallsParams, CallHierarchyItem,
     CallHierarchyOutgoingCall, CallHierarchyOutgoingCallsParams, CallHierarchyPrepareParams,
-    CodeAction, CodeActionResponse, CodeLens, Command, CompletionItem, Diagnostic,
-    DocumentFormattingParams, DocumentHighlight, DocumentSymbol, FoldingRange, FoldingRangeParams,
-    Hover, HoverContents, Location, MarkupContent, MarkupKind, Position, PrepareRenameResponse,
-    Range, RenameParams, SemanticTokensParams, SemanticTokensRangeParams,
-    SemanticTokensRangeResult, SemanticTokensResult, SymbolInformation, TextDocumentIdentifier,
-    TextEdit, Url, WorkspaceEdit,
+    CodeLens, Command, CompletionItem, Diagnostic, DocumentFormattingParams, DocumentHighlight,
+    DocumentSymbol, FoldingRange, FoldingRangeParams, Hover, HoverContents, Location,
+    MarkupContent, MarkupKind, Position, PrepareRenameResponse, Range, RenameParams,
+    SemanticTokensParams, SemanticTokensRangeParams, SemanticTokensRangeResult,
+    SemanticTokensResult, SymbolInformation, TextDocumentIdentifier, TextEdit, Url, WorkspaceEdit,
 };
 use ra_ide::{
     Assist, FileId, FilePosition, FileRange, Query, RangeInfo, Runnable, RunnableKind, SearchScope,
@@ -476,7 +475,7 @@ pub fn handle_completion(
         return Ok(None);
     }
 
-    let items = match world.analysis().completions(position, &world.config.completion)? {
+    let items = match world.analysis().completions(&world.config.completion, position)? {
         None => return Ok(None),
         Some(items) => items,
     };
@@ -585,9 +584,8 @@ pub fn handle_rename(world: WorldSnapshot, params: RenameParams) -> Result<Optio
         None => return Ok(None),
         Some(it) => it.info,
     };
-
-    let source_change = to_proto::source_change(&world, source_change)?;
-    Ok(Some(source_change.workspace_edit))
+    let workspace_edit = to_proto::workspace_edit(&world, source_change)?;
+    Ok(Some(workspace_edit))
 }
 
 pub fn handle_references(
@@ -696,14 +694,21 @@ pub fn handle_formatting(
 pub fn handle_code_action(
     world: WorldSnapshot,
     params: lsp_types::CodeActionParams,
-) -> Result<Option<CodeActionResponse>> {
+) -> Result<Option<Vec<lsp_ext::CodeAction>>> {
     let _p = profile("handle_code_action");
+    // We intentionally don't support command-based actions, as those either
+    // requires custom client-code anyway, or requires server-initiated edits.
+    // Server initiated edits break causality, so we avoid those as well.
+    if !world.config.client_caps.code_action_literals {
+        return Ok(None);
+    }
+
     let file_id = from_proto::file_id(&world, &params.text_document.uri)?;
     let line_index = world.analysis().file_line_index(file_id)?;
     let range = from_proto::text_range(&line_index, params.range);
 
     let diagnostics = world.analysis().diagnostics(file_id)?;
-    let mut res = CodeActionResponse::default();
+    let mut res: Vec<lsp_ext::CodeAction> = Vec::new();
 
     let fixes_from_diagnostics = diagnostics
         .into_iter()
@@ -713,22 +718,9 @@ pub fn handle_code_action(
 
     for source_edit in fixes_from_diagnostics {
         let title = source_edit.label.clone();
-        let edit = to_proto::source_change(&world, source_edit)?;
-
-        let command = Command {
-            title,
-            command: "rust-analyzer.applySourceChange".to_string(),
-            arguments: Some(vec![to_value(edit).unwrap()]),
-        };
-        let action = CodeAction {
-            title: command.title.clone(),
-            kind: None,
-            diagnostics: None,
-            edit: None,
-            command: Some(command),
-            is_preferred: None,
-        };
-        res.push(action.into());
+        let edit = to_proto::snippet_workspace_edit(&world, source_edit)?;
+        let action = lsp_ext::CodeAction { title, kind: None, edit: Some(edit), command: None };
+        res.push(action);
     }
 
     for fix in world.check_fixes.get(&file_id).into_iter().flatten() {
@@ -740,14 +732,21 @@ pub fn handle_code_action(
     }
 
     let mut grouped_assists: FxHashMap<String, (usize, Vec<Assist>)> = FxHashMap::default();
-    for assist in world.analysis().assists(FileRange { file_id, range })?.into_iter() {
+    for assist in
+        world.analysis().assists(&world.config.assist, FileRange { file_id, range })?.into_iter()
+    {
         match &assist.group_label {
             Some(label) => grouped_assists
                 .entry(label.to_owned())
                 .or_insert_with(|| {
                     let idx = res.len();
-                    let dummy = Command::new(String::new(), String::new(), None);
-                    res.push(dummy.into());
+                    let dummy = lsp_ext::CodeAction {
+                        title: String::new(),
+                        kind: None,
+                        command: None,
+                        edit: None,
+                    };
+                    res.push(dummy);
                     (idx, Vec::new())
                 })
                 .1
@@ -775,35 +774,10 @@ pub fn handle_code_action(
                 command: "rust-analyzer.selectAndApplySourceChange".to_string(),
                 arguments: Some(vec![serde_json::Value::Array(arguments)]),
             });
-            res[idx] = CodeAction {
-                title,
-                kind: None,
-                diagnostics: None,
-                edit: None,
-                command,
-                is_preferred: None,
-            }
-            .into();
+            res[idx] = lsp_ext::CodeAction { title, kind: None, edit: None, command };
         }
     }
 
-    // If the client only supports commands then filter the list
-    // and remove and actions that depend on edits.
-    if !world.config.client_caps.code_action_literals {
-        // FIXME: use drain_filter once it hits stable.
-        res = res
-            .into_iter()
-            .filter_map(|it| match it {
-                cmd @ lsp_types::CodeActionOrCommand::Command(_) => Some(cmd),
-                lsp_types::CodeActionOrCommand::CodeAction(action) => match action.command {
-                    Some(cmd) if action.edit.is_none() => {
-                        Some(lsp_types::CodeActionOrCommand::Command(cmd))
-                    }
-                    _ => None,
-                },
-            })
-            .collect();
-    }
     Ok(Some(res))
 }
 
diff --git a/crates/rust-analyzer/src/to_proto.rs b/crates/rust-analyzer/src/to_proto.rs
index a8e2e535f..2b1a3378f 100644
--- a/crates/rust-analyzer/src/to_proto.rs
+++ b/crates/rust-analyzer/src/to_proto.rs
@@ -112,6 +112,22 @@ pub(crate) fn text_edit(
     lsp_types::TextEdit { range, new_text }
 }
 
+pub(crate) fn snippet_text_edit(
+    line_index: &LineIndex,
+    line_endings: LineEndings,
+    is_snippet: bool,
+    indel: Indel,
+) -> lsp_ext::SnippetTextEdit {
+    let text_edit = text_edit(line_index, line_endings, indel);
+    let insert_text_format =
+        if is_snippet { Some(lsp_types::InsertTextFormat::Snippet) } else { None };
+    lsp_ext::SnippetTextEdit {
+        range: text_edit.range,
+        new_text: text_edit.new_text,
+        insert_text_format,
+    }
+}
+
 pub(crate) fn text_edit_vec(
     line_index: &LineIndex,
     line_endings: LineEndings,
@@ -441,10 +457,11 @@ pub(crate) fn goto_definition_response(
     }
 }
 
-pub(crate) fn text_document_edit(
+pub(crate) fn snippet_text_document_edit(
     world: &WorldSnapshot,
+    is_snippet: bool,
     source_file_edit: SourceFileEdit,
-) -> Result<lsp_types::TextDocumentEdit> {
+) -> Result<lsp_ext::SnippetTextDocumentEdit> {
     let text_document = versioned_text_document_identifier(world, source_file_edit.file_id, None)?;
     let line_index = world.analysis().file_line_index(source_file_edit.file_id)?;
     let line_endings = world.file_line_endings(source_file_edit.file_id);
@@ -452,9 +469,9 @@ pub(crate) fn text_document_edit(
         .edit
         .as_indels()
         .iter()
-        .map(|it| text_edit(&line_index, line_endings, it.clone()))
+        .map(|it| snippet_text_edit(&line_index, line_endings, is_snippet, it.clone()))
         .collect();
-    Ok(lsp_types::TextDocumentEdit { text_document, edits })
+    Ok(lsp_ext::SnippetTextDocumentEdit { text_document, edits })
 }
 
 pub(crate) fn resource_op(
@@ -500,20 +517,70 @@ pub(crate) fn source_change(
             })
         }
     };
-    let mut document_changes: Vec<lsp_types::DocumentChangeOperation> = Vec::new();
+    let label = source_change.label.clone();
+    let workspace_edit = self::snippet_workspace_edit(world, source_change)?;
+    Ok(lsp_ext::SourceChange { label, workspace_edit, cursor_position })
+}
+
+pub(crate) fn snippet_workspace_edit(
+    world: &WorldSnapshot,
+    source_change: SourceChange,
+) -> Result<lsp_ext::SnippetWorkspaceEdit> {
+    let mut document_changes: Vec<lsp_ext::SnippetDocumentChangeOperation> = Vec::new();
     for op in source_change.file_system_edits {
         let op = resource_op(&world, op)?;
-        document_changes.push(lsp_types::DocumentChangeOperation::Op(op));
+        document_changes.push(lsp_ext::SnippetDocumentChangeOperation::Op(op));
     }
     for edit in source_change.source_file_edits {
-        let edit = text_document_edit(&world, edit)?;
-        document_changes.push(lsp_types::DocumentChangeOperation::Edit(edit));
+        let edit = snippet_text_document_edit(&world, source_change.is_snippet, edit)?;
+        document_changes.push(lsp_ext::SnippetDocumentChangeOperation::Edit(edit));
+    }
+    let workspace_edit =
+        lsp_ext::SnippetWorkspaceEdit { changes: None, document_changes: Some(document_changes) };
+    Ok(workspace_edit)
+}
+
+pub(crate) fn workspace_edit(
+    world: &WorldSnapshot,
+    source_change: SourceChange,
+) -> Result<lsp_types::WorkspaceEdit> {
+    assert!(!source_change.is_snippet);
+    snippet_workspace_edit(world, source_change).map(|it| it.into())
+}
+
+impl From<lsp_ext::SnippetWorkspaceEdit> for lsp_types::WorkspaceEdit {
+    fn from(snippet_workspace_edit: lsp_ext::SnippetWorkspaceEdit) -> lsp_types::WorkspaceEdit {
+        lsp_types::WorkspaceEdit {
+            changes: None,
+            document_changes: snippet_workspace_edit.document_changes.map(|changes| {
+                lsp_types::DocumentChanges::Operations(
+                    changes
+                        .into_iter()
+                        .map(|change| match change {
+                            lsp_ext::SnippetDocumentChangeOperation::Op(op) => {
+                                lsp_types::DocumentChangeOperation::Op(op)
+                            }
+                            lsp_ext::SnippetDocumentChangeOperation::Edit(edit) => {
+                                lsp_types::DocumentChangeOperation::Edit(
+                                    lsp_types::TextDocumentEdit {
+                                        text_document: edit.text_document,
+                                        edits: edit
+                                            .edits
+                                            .into_iter()
+                                            .map(|edit| lsp_types::TextEdit {
+                                                range: edit.range,
+                                                new_text: edit.new_text,
+                                            })
+                                            .collect(),
+                                    },
+                                )
+                            }
+                        })
+                        .collect(),
+                )
+            }),
+        }
     }
-    let workspace_edit = lsp_types::WorkspaceEdit {
-        changes: None,
-        document_changes: Some(lsp_types::DocumentChanges::Operations(document_changes)),
-    };
-    Ok(lsp_ext::SourceChange { label: source_change.label, workspace_edit, cursor_position })
 }
 
 pub fn call_hierarchy_item(
@@ -571,22 +638,25 @@ fn main() <fold>{
     }
 }
 
-pub(crate) fn code_action(world: &WorldSnapshot, assist: Assist) -> Result<lsp_types::CodeAction> {
-    let source_change = source_change(&world, assist.source_change)?;
-    let arg = serde_json::to_value(source_change)?;
-    let title = assist.label;
-    let command = lsp_types::Command {
-        title: title.clone(),
-        command: "rust-analyzer.applySourceChange".to_string(),
-        arguments: Some(vec![arg]),
-    };
+pub(crate) fn code_action(world: &WorldSnapshot, assist: Assist) -> Result<lsp_ext::CodeAction> {
+    let res = if assist.source_change.is_snippet {
+        lsp_ext::CodeAction {
+            title: assist.label,
+            kind: Some(String::new()),
+            edit: Some(snippet_workspace_edit(world, assist.source_change)?),
+            command: None,
+        }
+    } else {
+        let source_change = source_change(&world, assist.source_change)?;
+        let arg = serde_json::to_value(source_change)?;
+        let title = assist.label;
+        let command = lsp_types::Command {
+            title: title.clone(),
+            command: "rust-analyzer.applySourceChange".to_string(),
+            arguments: Some(vec![arg]),
+        };
 
-    Ok(lsp_types::CodeAction {
-        title,
-        kind: Some(String::new()),
-        diagnostics: None,
-        edit: None,
-        command: Some(command),
-        is_preferred: None,
-    })
+        lsp_ext::CodeAction { title, kind: Some(String::new()), edit: None, command: Some(command) }
+    };
+    Ok(res)
 }
diff --git a/crates/rust-analyzer/tests/heavy_tests/main.rs b/crates/rust-analyzer/tests/heavy_tests/main.rs
index 5011cc273..74676b3ee 100644
--- a/crates/rust-analyzer/tests/heavy_tests/main.rs
+++ b/crates/rust-analyzer/tests/heavy_tests/main.rs
@@ -333,29 +333,17 @@ fn main() {}
             partial_result_params: PartialResultParams::default(),
             work_done_progress_params: WorkDoneProgressParams::default(),
         },
-        json!([
-          {
-            "command": {
-              "arguments": [
+        json!([{
+            "edit": {
+              "documentChanges": [
                 {
-                  "cursorPosition": null,
-                  "label": "Create module",
-                  "workspaceEdit": {
-                    "documentChanges": [
-                      {
-                        "kind": "create",
-                        "uri": "file:///[..]/src/bar.rs"
-                      }
-                    ]
-                  }
+                  "kind": "create",
+                  "uri": "file:///[..]/src/bar.rs"
                 }
-              ],
-              "command": "rust-analyzer.applySourceChange",
-              "title": "Create module"
+              ]
             },
             "title": "Create module"
-          }
-        ]),
+        }]),
     );
 
     server.request::<CodeActionRequest>(
@@ -416,29 +404,17 @@ fn main() {{}}
             partial_result_params: PartialResultParams::default(),
             work_done_progress_params: WorkDoneProgressParams::default(),
         },
-        json!([
-          {
-            "command": {
-              "arguments": [
+        json!([{
+            "edit": {
+              "documentChanges": [
                 {
-                  "cursorPosition": null,
-                  "label": "Create module",
-                  "workspaceEdit": {
-                    "documentChanges": [
-                      {
-                        "kind": "create",
-                        "uri": "file:///[..]/src/bar.rs"
-                      }
-                    ]
-                  }
+                  "kind": "create",
+                  "uri": "file://[..]/src/bar.rs"
                 }
-              ],
-              "command": "rust-analyzer.applySourceChange",
-              "title": "Create module"
+              ]
             },
             "title": "Create module"
-          }
-        ]),
+        }]),
     );
 
     server.request::<CodeActionRequest>(