5 files changed, 85 insertions, 25 deletions

diff --git a/crates/libeditor/src/code_actions.rs b/crates/libeditor/src/code_actions.rs
index 1e20c0f48..6c41923dd 100644
--- a/crates/libeditor/src/code_actions.rs
+++ b/crates/libeditor/src/code_actions.rs
@@ -1,4 +1,7 @@
-use {TextUnit, EditBuilder, Edit};
+use std::{
+    fmt::{self, Write},
+};
+
 use libsyntax2::{
     ast::{self, AstNode, AttrsOwner, TypeParamsOwner, NameOwner, ParsedFile},
     SyntaxKind::COMMA,
@@ -9,6 +12,8 @@ use libsyntax2::{
     },
 };
 
+use {TextUnit, EditBuilder, Edit};
+
 pub struct ActionResult {
     pub edit: Edit,
     pub cursor_position: Option<TextUnit>,
@@ -63,27 +68,31 @@ pub fn add_impl<'a>(file: &'a ParsedFile, offset: TextUnit) -> Option<impl FnOnc
     let name = nominal.name()?;
 
     Some(move || {
-        // let type_params = nominal.type_param_list();
-        // let type_args = match type_params {
-        //     None => String::new(),
-        //     Some(params) => {
-        //         let mut buf = String::new();
-        //     }
-        // };
+        let type_params = nominal.type_param_list();
         let mut edit = EditBuilder::new();
         let start_offset = nominal.syntax().range().end();
-        edit.insert(
-            start_offset,
-            format!(
-                "\n\nimpl {} {{\n\n}}",
-                name.text(),
-            )
-        );
+        let mut buf = String::new();
+        buf.push_str("\n\nimpl");
+        if let Some(type_params) = type_params {
+            buf.push_display(&type_params.syntax().text());
+        }
+        buf.push_str(" ");
+        buf.push_str(name.text().as_str());
+        if let Some(type_params) = type_params {
+            comma_list(
+                &mut buf, "<", ">",
+                type_params.type_params()
+                    .filter_map(|it| it.name())
+                    .map(|it| it.text())
+            );
+        }
+        buf.push_str(" {\n");
+        let offset = start_offset + TextUnit::of_str(&buf);
+        buf.push_str("\n}");
+        edit.insert(start_offset, buf);
         ActionResult {
             edit: edit.finish(),
-            cursor_position: Some(
-                start_offset + TextUnit::of_str("\n\nimpl  {\n") + name.syntax().range().len()
-            ),
+            cursor_position: Some(offset),
         }
     })
 }
@@ -104,3 +113,26 @@ pub fn find_node<'a, N: AstNode<'a>>(syntax: SyntaxNodeRef<'a>, offset: TextUnit
         .next()
 }
 
+fn comma_list(buf: &mut String, bra: &str, ket: &str, items: impl Iterator<Item=impl fmt::Display>) {
+    buf.push_str(bra);
+    let mut first = true;
+    for item in items {
+        if !first {
+            first = false;
+            buf.push_str(", ");
+        }
+        write!(buf, "{}", item).unwrap();
+    }
+    buf.push_str(ket);
+}
+
+trait PushDisplay {
+    fn push_display<T: fmt::Display>(&mut self, item: &T);
+}
+
+impl PushDisplay for String {
+    fn push_display<T: fmt::Display>(&mut self, item: &T) {
+        use std::fmt::Write;
+        write!(self, "{}", item).unwrap()
+    }
+}
diff --git a/crates/libeditor/tests/test.rs b/crates/libeditor/tests/test.rs
index 3b0ec78eb..42926ffc8 100644
--- a/crates/libeditor/tests/test.rs
+++ b/crates/libeditor/tests/test.rs
@@ -151,11 +151,11 @@ fn test_add_impl() {
         "struct Foo {}\n\nimpl Foo {\n<|>\n}\n",
         |file, off| add_impl(file, off).map(|f| f()),
     );
-    // check_action(
-    //     "struct Foo<T: Clone> {<|>}",
-    //     "struct Foo<T: Clone> {}\nimpl<T: Clone> Foo<T> {\n<|>\n}",
-    //     |file, off| add_impl(file, off).map(|f| f()),
-    // );
+    check_action(
+        "struct Foo<T: Clone> {<|>}",
+        "struct Foo<T: Clone> {}\n\nimpl<T: Clone> Foo<T> {\n<|>\n}",
+        |file, off| add_impl(file, off).map(|f| f()),
+    );
 }
 
 #[test]
diff --git a/crates/libsyntax2/src/ast/generated.rs b/crates/libsyntax2/src/ast/generated.rs
index 6df1d2311..5edb9faaa 100644
--- a/crates/libsyntax2/src/ast/generated.rs
+++ b/crates/libsyntax2/src/ast/generated.rs
@@ -580,6 +580,25 @@ impl<'a> ast::TypeParamsOwner<'a> for TypeDef<'a> {}
 impl<'a> ast::AttrsOwner<'a> for TypeDef<'a> {}
 impl<'a> TypeDef<'a> {}
 
+// TypeParam
+#[derive(Debug, Clone, Copy)]
+pub struct TypeParam<'a> {
+    syntax: SyntaxNodeRef<'a>,
+}
+
+impl<'a> AstNode<'a> for TypeParam<'a> {
+    fn cast(syntax: SyntaxNodeRef<'a>) -> Option<Self> {
+        match syntax.kind() {
+            TYPE_PARAM => Some(TypeParam { syntax }),
+            _ => None,
+        }
+    }
+    fn syntax(self) -> SyntaxNodeRef<'a> { self.syntax }
+}
+
+impl<'a> ast::NameOwner<'a> for TypeParam<'a> {}
+impl<'a> TypeParam<'a> {}
+
 // TypeParamList
 #[derive(Debug, Clone, Copy)]
 pub struct TypeParamList<'a> {
@@ -596,7 +615,11 @@ impl<'a> AstNode<'a> for TypeParamList<'a> {
     fn syntax(self) -> SyntaxNodeRef<'a> { self.syntax }
 }
 
-impl<'a> TypeParamList<'a> {}
+impl<'a> TypeParamList<'a> {
+    pub fn type_params(self) -> impl Iterator<Item = TypeParam<'a>> + 'a {
+        super::children(self)
+    }
+}
 
 // TypeRef
 #[derive(Debug, Clone, Copy)]
diff --git a/crates/libsyntax2/src/grammar.ron b/crates/libsyntax2/src/grammar.ron
index e56496be1..daf80dde3 100644
--- a/crates/libsyntax2/src/grammar.ron
+++ b/crates/libsyntax2/src/grammar.ron
@@ -310,7 +310,8 @@ Grammar(
         "NameRef": (),
         "Attr": ( options: [ ["value", "TokenTree"] ] ),
         "TokenTree": (),
-        "TypeParamList": (),
+        "TypeParamList": ( collections: [ ["type_params", "TypeParam" ] ]),
+        "TypeParam": ( traits: ["NameOwner"]),
         "WhereClause": (),
     },
 )
diff --git a/crates/server/src/main_loop/handlers.rs b/crates/server/src/main_loop/handlers.rs
index 9ff821a8b..b47cbc0fc 100644
--- a/crates/server/src/main_loop/handlers.rs
+++ b/crates/server/src/main_loop/handlers.rs
@@ -110,6 +110,7 @@ pub fn handle_code_action(
     let actions = &[
         (ActionId::FlipComma, libeditor::flip_comma(&file, offset).is_some()),
         (ActionId::AddDerive, libeditor::add_derive(&file, offset).is_some()),
+        (ActionId::AddImpl, libeditor::add_impl(&file, offset).is_some()),
     ];
 
     for (id, edit) in actions {
@@ -218,6 +219,7 @@ pub fn handle_execute_command(
     let action_result = match arg.id {
         ActionId::FlipComma => libeditor::flip_comma(&file, arg.offset).map(|f| f()),
         ActionId::AddDerive => libeditor::add_derive(&file, arg.offset).map(|f| f()),
+        ActionId::AddImpl => libeditor::add_impl(&file, arg.offset).map(|f| f()),
     }.ok_or_else(|| format_err!("command not applicable"))?;
     let line_index = world.analysis().file_line_index(file_id)?;
     let mut changes = HashMap::new();
@@ -259,6 +261,7 @@ fn apply_code_action_cmd(id: ActionId, doc: TextDocumentIdentifier, offset: Text
 enum ActionId {
     FlipComma,
     AddDerive,
+    AddImpl,
 }
 
 impl ActionId {
@@ -266,6 +269,7 @@ impl ActionId {
         match *self {
             ActionId::FlipComma => "Flip `,`",
             ActionId::AddDerive => "Add `#[derive]`",
+            ActionId::AddImpl => "Add impl",
         }
     }
 }