7 files changed, 262 insertions, 20 deletions

diff --git a/crates/ra_assists/src/assists/add_derive.rs b/crates/ra_assists/src/assists/add_derive.rs
index 77ecc33c9..d3ba634c4 100644
--- a/crates/ra_assists/src/assists/add_derive.rs
+++ b/crates/ra_assists/src/assists/add_derive.rs
@@ -1,5 +1,3 @@
-//! FIXME: write short doc here
-
 use hir::db::HirDatabase;
 use ra_syntax::{
     ast::{self, AstNode, AttrsOwner},
@@ -9,6 +7,22 @@ use ra_syntax::{
 
 use crate::{Assist, AssistCtx, AssistId};
 
+// Assist: add_derive
+// Adds a new `#[derive()]` clause to a struct or enum.
+// ```
+// struct Point {
+//     x: u32,
+//     y: u32,<|>
+// }
+// ```
+// ->
+// ```
+// #[derive()]
+// struct Point {
+//     x: u32,
+//     y: u32,
+// }
+// ```
 pub(crate) fn add_derive(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let nominal = ctx.node_at_offset::<ast::NominalDef>()?;
     let node_start = derive_insertion_offset(&nominal)?;
diff --git a/crates/ra_assists/src/assists/add_explicit_type.rs b/crates/ra_assists/src/assists/add_explicit_type.rs
index 8c83dc987..33b7bea7f 100644
--- a/crates/ra_assists/src/assists/add_explicit_type.rs
+++ b/crates/ra_assists/src/assists/add_explicit_type.rs
@@ -1,5 +1,3 @@
-//! FIXME: write short doc here
-
 use hir::{db::HirDatabase, HirDisplay, Ty};
 use ra_syntax::{
     ast::{self, AstNode, LetStmt, NameOwner},
@@ -8,7 +6,19 @@ use ra_syntax::{
 
 use crate::{Assist, AssistCtx, AssistId};
 
-/// Add explicit type assist.
+// Assist: add_explicit_type
+// Specify type for a let binding
+// ```
+// fn main() {
+//     let x<|> = 92;
+// }
+// ```
+// ->
+// ```
+// fn main() {
+//     let x: i32 = 92;
+// }
+// ```
 pub(crate) fn add_explicit_type(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let stmt = ctx.node_at_offset::<LetStmt>()?;
     let expr = stmt.initializer()?;
diff --git a/crates/ra_assists/src/assists/add_impl.rs b/crates/ra_assists/src/assists/add_impl.rs
index 94801fbc9..40bc5c464 100644
--- a/crates/ra_assists/src/assists/add_impl.rs
+++ b/crates/ra_assists/src/assists/add_impl.rs
@@ -1,5 +1,3 @@
-//! FIXME: write short doc here
-
 use format_buf::format;
 use hir::db::HirDatabase;
 use join_to_string::join;
@@ -10,6 +8,23 @@ use ra_syntax::{
 
 use crate::{Assist, AssistCtx, AssistId};
 
+// Assist: add_impl
+// Adds a new inherent impl for a type
+// ```
+// struct Ctx<T: Clone> {
+//      data: T,<|>
+// }
+// ```
+// ->
+// ```
+// struct Ctx<T: Clone> {
+//      data: T,
+// }
+//
+// impl<T: Clone> Ctx<T> {
+//
+// }
+// ```
 pub(crate) fn add_impl(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let nominal = ctx.node_at_offset::<ast::NominalDef>()?;
     let name = nominal.name()?;
diff --git a/crates/ra_assists/src/assists/add_missing_impl_members.rs b/crates/ra_assists/src/assists/add_missing_impl_members.rs
index 565b96fb5..36fa6f9ea 100644
--- a/crates/ra_assists/src/assists/add_missing_impl_members.rs
+++ b/crates/ra_assists/src/assists/add_missing_impl_members.rs
@@ -1,5 +1,3 @@
-//! FIXME: write short doc here
-
 use hir::{db::HirDatabase, HasSource};
 use ra_syntax::{
     ast::{self, edit, make, AstNode, NameOwner},
@@ -14,6 +12,32 @@ enum AddMissingImplMembersMode {
     NoDefaultMethods,
 }
 
+// Assist: add_impl_missing_members
+// Adds scaffold for required impl members
+// ```
+// trait T {
+//     Type X;
+//     fn foo(&self);
+//     fn bar(&self) {}
+// }
+//
+// impl T for () {<|>
+//
+// }
+// ```
+// ->
+// ```
+// trait T {
+//     Type X;
+//     fn foo(&self);
+//     fn bar(&self) {}
+// }
+//
+// impl T for () {
+//     fn foo(&self) { unimplemented!() }
+//
+// }
+// ```
 pub(crate) fn add_missing_impl_members(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     add_missing_impl_members_inner(
         ctx,
@@ -23,6 +47,36 @@ pub(crate) fn add_missing_impl_members(ctx: AssistCtx<impl HirDatabase>) -> Opti
     )
 }
 
+// Assist: add_impl_default_members
+// Adds scaffold for overriding default impl members
+// ```
+// trait T {
+//     Type X;
+//     fn foo(&self);
+//     fn bar(&self) {}
+// }
+//
+// impl T for () {
+//     Type X = ();
+//     fn foo(&self) {}<|>
+//
+// }
+// ```
+// ->
+// ```
+// trait T {
+//     Type X;
+//     fn foo(&self);
+//     fn bar(&self) {}
+// }
+//
+// impl T for () {
+//     Type X = ();
+//     fn foo(&self) {}
+//     fn bar(&self) {}
+//
+// }
+// ```
 pub(crate) fn add_missing_default_members(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     add_missing_impl_members_inner(
         ctx,
diff --git a/crates/ra_assists/src/assists/apply_demorgan.rs b/crates/ra_assists/src/assists/apply_demorgan.rs
index 5f2b0dd18..a072f63e7 100644
--- a/crates/ra_assists/src/assists/apply_demorgan.rs
+++ b/crates/ra_assists/src/assists/apply_demorgan.rs
@@ -1,18 +1,26 @@
-//! This contains the functions associated with the demorgan assist.
-//! This assist transforms boolean expressions of the form `!a || !b` into
-//! `!(a && b)`.
 use hir::db::HirDatabase;
 use ra_syntax::ast::{self, AstNode};
 use ra_syntax::SyntaxNode;
 
 use crate::{Assist, AssistCtx, AssistId};
 
-/// Assist for applying demorgan's law
-///
-/// This transforms expressions of the form `!l || !r` into `!(l && r)`.
-/// This also works with `&&`. This assist can only be applied with the cursor
-/// on either `||` or `&&`, with both operands being a negation of some kind.
-/// This means something of the form `!x` or `x != y`.
+// Assist: apply_demorgan
+// Apply [De Morgan's law](https://en.wikipedia.org/wiki/De_Morgan%27s_laws).
+// This transforms expressions of the form `!l || !r` into `!(l && r)`.
+// This also works with `&&`. This assist can only be applied with the cursor
+// on either `||` or `&&`, with both operands being a negation of some kind.
+// This means something of the form `!x` or `x != y`.
+// ```
+// fn main() {
+//     if x != 4 ||<|> !y {}
+// }
+// ```
+// ->
+// ```
+// fn main() {
+//     if !(x == 4 && y) {}
+// }
+// ```
 pub(crate) fn apply_demorgan(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let expr = ctx.node_at_offset::<ast::BinExpr>()?;
     let op = expr.op_kind()?;
diff --git a/crates/ra_assists/src/doc_tests.rs b/crates/ra_assists/src/doc_tests.rs
index 88e901517..872bbdf17 100644
--- a/crates/ra_assists/src/doc_tests.rs
+++ b/crates/ra_assists/src/doc_tests.rs
@@ -15,8 +15,10 @@ fn check(assist_id: &str, before: &str, after: &str) {
     let (db, _source_root, file_id) = MockDatabase::with_single_file(&before);
     let frange = FileRange { file_id, range: TextRange::offset_len(before_cursor_pos, 0.into()) };
 
-    let (_assist_id, action) =
-        crate::assists(&db, frange).into_iter().find(|(id, _)| id.id.0 == assist_id).unwrap();
+    let (_assist_id, action) = crate::assists(&db, frange)
+        .into_iter()
+        .find(|(id, _)| id.id.0 == assist_id)
+        .unwrap_or_else(|| panic!("Assist {:?} is not applicable", assist_id));
 
     let actual = action.edit.apply(&before);
     assert_eq_text!(after, &actual);
diff --git a/crates/ra_assists/src/doc_tests/generated.rs b/crates/ra_assists/src/doc_tests/generated.rs
index e5f6910f1..76d86b93d 100644
--- a/crates/ra_assists/src/doc_tests/generated.rs
+++ b/crates/ra_assists/src/doc_tests/generated.rs
@@ -3,6 +3,145 @@
 use super::check;
 
 #[test]
+fn doctest_add_derive() {
+    check(
+        "add_derive",
+        r#####"
+struct Point {
+    x: u32,
+    y: u32,<|>
+}
+"#####,
+        r#####"
+#[derive()]
+struct Point {
+    x: u32,
+    y: u32,
+}
+"#####,
+    )
+}
+
+#[test]
+fn doctest_add_explicit_type() {
+    check(
+        "add_explicit_type",
+        r#####"
+fn main() {
+    let x<|> = 92;
+}
+"#####,
+        r#####"
+fn main() {
+    let x: i32 = 92;
+}
+"#####,
+    )
+}
+
+#[test]
+fn doctest_add_impl() {
+    check(
+        "add_impl",
+        r#####"
+struct Ctx<T: Clone> {
+     data: T,<|>
+}
+"#####,
+        r#####"
+struct Ctx<T: Clone> {
+     data: T,
+}
+
+impl<T: Clone> Ctx<T> {
+
+}
+"#####,
+    )
+}
+
+#[test]
+fn doctest_add_impl_default_members() {
+    check(
+        "add_impl_default_members",
+        r#####"
+trait T {
+    Type X;
+    fn foo(&self);
+    fn bar(&self) {}
+}
+
+impl T for () {
+    Type X = ();
+    fn foo(&self) {}<|>
+
+}
+"#####,
+        r#####"
+trait T {
+    Type X;
+    fn foo(&self);
+    fn bar(&self) {}
+}
+
+impl T for () {
+    Type X = ();
+    fn foo(&self) {}
+    fn bar(&self) {}
+
+}
+"#####,
+    )
+}
+
+#[test]
+fn doctest_add_impl_missing_members() {
+    check(
+        "add_impl_missing_members",
+        r#####"
+trait T {
+    Type X;
+    fn foo(&self);
+    fn bar(&self) {}
+}
+
+impl T for () {<|>
+
+}
+"#####,
+        r#####"
+trait T {
+    Type X;
+    fn foo(&self);
+    fn bar(&self) {}
+}
+
+impl T for () {
+    fn foo(&self) { unimplemented!() }
+
+}
+"#####,
+    )
+}
+
+#[test]
+fn doctest_apply_demorgan() {
+    check(
+        "apply_demorgan",
+        r#####"
+fn main() {
+    if x != 4 ||<|> !y {}
+}
+"#####,
+        r#####"
+fn main() {
+    if !(x == 4 && y) {}
+}
+"#####,
+    )
+}
+
+#[test]
 fn doctest_convert_to_guarded_return() {
     check(
         "convert_to_guarded_return",