23 files changed, 178 insertions, 355 deletions

diff --git a/crates/ra_assists/src/assist_ctx.rs b/crates/ra_assists/src/assist_ctx.rs
index c45262efa..189cad7d0 100644
--- a/crates/ra_assists/src/assist_ctx.rs
+++ b/crates/ra_assists/src/assist_ctx.rs
@@ -1,8 +1,10 @@
+//! FIXME: write short doc here
+
 use hir::db::HirDatabase;
 use ra_db::FileRange;
 use ra_fmt::{leading_indent, reindent};
 use ra_syntax::{
-    algo::{find_covering_element, find_node_at_offset},
+    algo::{self, find_covering_element, find_node_at_offset},
     AstNode, SourceFile, SyntaxElement, SyntaxNode, SyntaxToken, TextRange, TextUnit,
     TokenAtOffset,
 };
@@ -177,6 +179,10 @@ impl AssistBuilder {
         &mut self.edit
     }
 
+    pub(crate) fn replace_ast<N: AstNode>(&mut self, old: N, new: N) {
+        algo::diff(old.syntax(), new.syntax()).into_text_edit(&mut self.edit)
+    }
+
     fn build(self) -> AssistAction {
         AssistAction {
             edit: self.edit.finish(),
diff --git a/crates/ra_assists/src/assists/add_derive.rs b/crates/ra_assists/src/assists/add_derive.rs
index 9c88644df..77ecc33c9 100644
--- a/crates/ra_assists/src/assists/add_derive.rs
+++ b/crates/ra_assists/src/assists/add_derive.rs
@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use hir::db::HirDatabase;
 use ra_syntax::{
     ast::{self, AstNode, AttrsOwner},
@@ -13,7 +15,7 @@ pub(crate) fn add_derive(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist>
     ctx.add_action(AssistId("add_derive"), "add `#[derive]`", |edit| {
         let derive_attr = nominal
             .attrs()
-            .filter_map(|x| x.as_call())
+            .filter_map(|x| x.as_simple_call())
             .filter(|(name, _arg)| name == "derive")
             .map(|(_name, arg)| arg)
             .next();
diff --git a/crates/ra_assists/src/assists/add_explicit_type.rs b/crates/ra_assists/src/assists/add_explicit_type.rs
index 78f0f7f28..8c83dc987 100644
--- a/crates/ra_assists/src/assists/add_explicit_type.rs
+++ b/crates/ra_assists/src/assists/add_explicit_type.rs
@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use hir::{db::HirDatabase, HirDisplay, Ty};
 use ra_syntax::{
     ast::{self, AstNode, LetStmt, NameOwner},
diff --git a/crates/ra_assists/src/assists/add_impl.rs b/crates/ra_assists/src/assists/add_impl.rs
index 4b61f4031..94801fbc9 100644
--- a/crates/ra_assists/src/assists/add_impl.rs
+++ b/crates/ra_assists/src/assists/add_impl.rs
@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use format_buf::format;
 use hir::db::HirDatabase;
 use join_to_string::join;
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 23da1e65f..565b96fb5 100644
--- a/crates/ra_assists/src/assists/add_missing_impl_members.rs
+++ b/crates/ra_assists/src/assists/add_missing_impl_members.rs
@@ -1,10 +1,12 @@
+//! FIXME: write short doc here
+
 use hir::{db::HirDatabase, HasSource};
 use ra_syntax::{
-    ast::{self, make, AstNode, NameOwner},
+    ast::{self, edit, make, AstNode, NameOwner},
     SmolStr,
 };
 
-use crate::{ast_editor::AstEditor, Assist, AssistCtx, AssistId};
+use crate::{Assist, AssistCtx, AssistId};
 
 #[derive(PartialEq)]
 enum AddMissingImplMembersMode {
@@ -75,37 +77,32 @@ fn add_missing_impl_members_inner(
 
     ctx.add_action(AssistId(assist_id), label, |edit| {
         let n_existing_items = impl_item_list.impl_items().count();
-        let items = missing_items.into_iter().map(|it| match it {
-            ast::ImplItem::FnDef(def) => strip_docstring(add_body(def).into()),
-            _ => strip_docstring(it),
-        });
-        let mut ast_editor = AstEditor::new(impl_item_list);
-
-        ast_editor.append_items(items);
-
-        let first_new_item = ast_editor.ast().impl_items().nth(n_existing_items).unwrap();
-        let cursor_position = first_new_item.syntax().text_range().start();
-        ast_editor.into_text_edit(edit.text_edit_builder());
-
+        let items = missing_items
+            .into_iter()
+            .map(|it| match it {
+                ast::ImplItem::FnDef(def) => ast::ImplItem::FnDef(add_body(def)),
+                _ => it,
+            })
+            .map(|it| edit::strip_attrs_and_docs(&it));
+        let new_impl_item_list = impl_item_list.append_items(items);
+        let cursor_position = {
+            let first_new_item = new_impl_item_list.impl_items().nth(n_existing_items).unwrap();
+            first_new_item.syntax().text_range().start()
+        };
+
+        edit.replace_ast(impl_item_list, new_impl_item_list);
         edit.set_cursor(cursor_position);
     });
 
     ctx.build()
 }
 
-fn strip_docstring(item: ast::ImplItem) -> ast::ImplItem {
-    let mut ast_editor = AstEditor::new(item);
-    ast_editor.strip_attrs_and_docs();
-    ast_editor.ast().to_owned()
-}
-
 fn add_body(fn_def: ast::FnDef) -> ast::FnDef {
-    let mut ast_editor = AstEditor::new(fn_def.clone());
     if fn_def.body().is_none() {
-        let body = make::block_from_expr(make::expr_unimplemented());
-        ast_editor.set_body(&body);
+        fn_def.with_body(make::block_from_expr(make::expr_unimplemented()))
+    } else {
+        fn_def
     }
-    ast_editor.ast().to_owned()
 }
 
 /// Given an `ast::ImplBlock`, resolves the target trait (the one being
@@ -332,5 +329,4 @@ impl Foo for S {
 }",
         )
     }
-
 }
diff --git a/crates/ra_assists/src/assists/apply_demorgan.rs b/crates/ra_assists/src/assists/apply_demorgan.rs
new file mode 100644
index 000000000..5f2b0dd18
--- /dev/null
+++ b/crates/ra_assists/src/assists/apply_demorgan.rs
@@ -0,0 +1,102 @@
+//! 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`.
+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()?;
+    let op_range = expr.op_token()?.text_range();
+    let opposite_op = opposite_logic_op(op)?;
+    let cursor_in_range = ctx.frange.range.is_subrange(&op_range);
+    if !cursor_in_range {
+        return None;
+    }
+    let lhs = expr.lhs()?.syntax().clone();
+    let lhs_range = lhs.text_range();
+    let rhs = expr.rhs()?.syntax().clone();
+    let rhs_range = rhs.text_range();
+    let not_lhs = undo_negation(lhs)?;
+    let not_rhs = undo_negation(rhs)?;
+
+    ctx.add_action(AssistId("apply_demorgan"), "apply demorgan's law", |edit| {
+        edit.target(op_range);
+        edit.replace(op_range, opposite_op);
+        edit.replace(lhs_range, format!("!({}", not_lhs));
+        edit.replace(rhs_range, format!("{})", not_rhs));
+    });
+    ctx.build()
+}
+
+// Return the opposite text for a given logical operator, if it makes sense
+fn opposite_logic_op(kind: ast::BinOp) -> Option<&'static str> {
+    match kind {
+        ast::BinOp::BooleanOr => Some("&&"),
+        ast::BinOp::BooleanAnd => Some("||"),
+        _ => None,
+    }
+}
+
+// This function tries to undo unary negation, or inequality
+fn undo_negation(node: SyntaxNode) -> Option<String> {
+    match ast::Expr::cast(node)? {
+        ast::Expr::BinExpr(bin) => match bin.op_kind()? {
+            ast::BinOp::NegatedEqualityTest => {
+                let lhs = bin.lhs()?.syntax().text();
+                let rhs = bin.rhs()?.syntax().text();
+                Some(format!("{} == {}", lhs, rhs))
+            }
+            _ => None,
+        },
+        ast::Expr::PrefixExpr(pe) => match pe.op_kind()? {
+            ast::PrefixOp::Not => {
+                let child = pe.expr()?.syntax().text();
+                Some(String::from(child))
+            }
+            _ => None,
+        },
+        _ => None,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    use crate::helpers::{check_assist, check_assist_not_applicable};
+
+    #[test]
+    fn demorgan_turns_and_into_or() {
+        check_assist(apply_demorgan, "fn f() { !x &&<|> !x }", "fn f() { !(x ||<|> x) }")
+    }
+
+    #[test]
+    fn demorgan_turns_or_into_and() {
+        check_assist(apply_demorgan, "fn f() { !x ||<|> !x }", "fn f() { !(x &&<|> x) }")
+    }
+
+    #[test]
+    fn demorgan_removes_inequality() {
+        check_assist(apply_demorgan, "fn f() { x != x ||<|> !x }", "fn f() { !(x == x &&<|> x) }")
+    }
+
+    #[test]
+    fn demorgan_doesnt_apply_with_cursor_not_on_op() {
+        check_assist_not_applicable(apply_demorgan, "fn f() { <|> !x || !x }")
+    }
+
+    #[test]
+    fn demorgan_doesnt_apply_when_operands_arent_negated_already() {
+        check_assist_not_applicable(apply_demorgan, "fn f() { x ||<|> x }")
+    }
+}
diff --git a/crates/ra_assists/src/assists/auto_import.rs b/crates/ra_assists/src/assists/auto_import.rs
index 5aae98546..02c58e7c6 100644
--- a/crates/ra_assists/src/assists/auto_import.rs
+++ b/crates/ra_assists/src/assists/auto_import.rs
@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use hir::{self, db::HirDatabase};
 use ra_text_edit::TextEditBuilder;
 
@@ -448,7 +450,6 @@ fn make_assist_add_in_tree_list(
         fmt_segments_raw(target, &mut buf);
         edit.insert(offset, buf);
     } else {
-
     }
 }
 
@@ -512,7 +513,7 @@ pub fn collect_hir_path_segments(path: &hir::Path) -> Option<Vec<SmolStr>> {
         hir::PathKind::Plain => {}
         hir::PathKind::Self_ => ps.push("self".into()),
         hir::PathKind::Super => ps.push("super".into()),
-        hir::PathKind::Type(_) => return None,
+        hir::PathKind::Type(_) | hir::PathKind::DollarCrate(_) => return None,
     }
     for s in path.segments.iter() {
         ps.push(s.name.to_string().into());
diff --git a/crates/ra_assists/src/assists/change_visibility.rs b/crates/ra_assists/src/assists/change_visibility.rs
index 60c74debc..df92c6b67 100644
--- a/crates/ra_assists/src/assists/change_visibility.rs
+++ b/crates/ra_assists/src/assists/change_visibility.rs
@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use hir::db::HirDatabase;
 use ra_syntax::{
     ast::{self, NameOwner, VisibilityOwner},
diff --git a/crates/ra_assists/src/assists/fill_match_arms.rs b/crates/ra_assists/src/assists/fill_match_arms.rs
index db82db89a..7335cce09 100644
--- a/crates/ra_assists/src/assists/fill_match_arms.rs
+++ b/crates/ra_assists/src/assists/fill_match_arms.rs
@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use std::iter;
 
 use hir::{db::HirDatabase, Adt, HasSource};
diff --git a/crates/ra_assists/src/assists/flip_binexpr.rs b/crates/ra_assists/src/assists/flip_binexpr.rs
index b55b36a8e..c51035282 100644
--- a/crates/ra_assists/src/assists/flip_binexpr.rs
+++ b/crates/ra_assists/src/assists/flip_binexpr.rs
@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use hir::db::HirDatabase;
 use ra_syntax::ast::{AstNode, BinExpr, BinOp};
 
diff --git a/crates/ra_assists/src/assists/flip_comma.rs b/crates/ra_assists/src/assists/flip_comma.rs
index 5ee7561bc..e31cc5e7d 100644
--- a/crates/ra_assists/src/assists/flip_comma.rs
+++ b/crates/ra_assists/src/assists/flip_comma.rs
@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use hir::db::HirDatabase;
 use ra_syntax::{algo::non_trivia_sibling, Direction, T};
 
diff --git a/crates/ra_assists/src/assists/inline_local_variable.rs b/crates/ra_assists/src/assists/inline_local_variable.rs
index eedb29199..9bd64decc 100644
--- a/crates/ra_assists/src/assists/inline_local_variable.rs
+++ b/crates/ra_assists/src/assists/inline_local_variable.rs
@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use hir::db::HirDatabase;
 use ra_syntax::{
     ast::{self, AstNode, AstToken},
diff --git a/crates/ra_assists/src/assists/introduce_variable.rs b/crates/ra_assists/src/assists/introduce_variable.rs
index 470ffe120..43378c4b0 100644
--- a/crates/ra_assists/src/assists/introduce_variable.rs
+++ b/crates/ra_assists/src/assists/introduce_variable.rs
@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use format_buf::format;
 use hir::db::HirDatabase;
 use ra_syntax::{
diff --git a/crates/ra_assists/src/assists/merge_match_arms.rs b/crates/ra_assists/src/assists/merge_match_arms.rs
index 3b6a99895..17baa98f9 100644
--- a/crates/ra_assists/src/assists/merge_match_arms.rs
+++ b/crates/ra_assists/src/assists/merge_match_arms.rs
@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use crate::{Assist, AssistCtx, AssistId, TextRange, TextUnit};
 use hir::db::HirDatabase;
 use ra_syntax::ast::{AstNode, MatchArm};
diff --git a/crates/ra_assists/src/assists/move_bounds.rs b/crates/ra_assists/src/assists/move_bounds.rs
index fd4bdc55c..f791d22b0 100644
--- a/crates/ra_assists/src/assists/move_bounds.rs
+++ b/crates/ra_assists/src/assists/move_bounds.rs
@@ -1,11 +1,13 @@
+//! FIXME: write short doc here
+
 use hir::db::HirDatabase;
 use ra_syntax::{
-    ast::{self, make, AstNode, NameOwner, TypeBoundsOwner},
+    ast::{self, edit, make, AstNode, NameOwner, TypeBoundsOwner},
     SyntaxElement,
     SyntaxKind::*,
 };
 
-use crate::{ast_editor::AstEditor, Assist, AssistCtx, AssistId};
+use crate::{Assist, AssistCtx, AssistId};
 
 pub(crate) fn move_bounds_to_where_clause(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let type_param_list = ctx.node_at_offset::<ast::TypeParamList>()?;
@@ -39,14 +41,12 @@ pub(crate) fn move_bounds_to_where_clause(mut ctx: AssistCtx<impl HirDatabase>)
                 .type_params()
                 .filter(|it| it.type_bound_list().is_some())
                 .map(|type_param| {
-                    let without_bounds =
-                        AstEditor::new(type_param.clone()).remove_bounds().ast().clone();
+                    let without_bounds = type_param.remove_bounds();
                     (type_param, without_bounds)
                 });
 
-            let mut ast_editor = AstEditor::new(type_param_list.clone());
-            ast_editor.replace_descendants(new_params);
-            ast_editor.into_text_edit(edit.text_edit_builder());
+            let new_type_param_list = edit::replace_descendants(&type_param_list, new_params);
+            edit.replace_ast(type_param_list.clone(), new_type_param_list);
 
             let where_clause = {
                 let predicates = type_param_list.type_params().filter_map(build_predicate);
diff --git a/crates/ra_assists/src/assists/move_guard.rs b/crates/ra_assists/src/assists/move_guard.rs
index 699221e33..51aea6334 100644
--- a/crates/ra_assists/src/assists/move_guard.rs
+++ b/crates/ra_assists/src/assists/move_guard.rs
@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use hir::db::HirDatabase;
 use ra_syntax::{
     ast,
diff --git a/crates/ra_assists/src/assists/raw_string.rs b/crates/ra_assists/src/assists/raw_string.rs
index 200aaa59a..2d2e31e51 100644
--- a/crates/ra_assists/src/assists/raw_string.rs
+++ b/crates/ra_assists/src/assists/raw_string.rs
@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use hir::db::HirDatabase;
 use ra_syntax::{ast::AstNode, ast::Literal, TextRange, TextUnit};
 use rustc_lexer;
diff --git a/crates/ra_assists/src/assists/remove_dbg.rs b/crates/ra_assists/src/assists/remove_dbg.rs
index 870133fda..1a7e2b305 100644
--- a/crates/ra_assists/src/assists/remove_dbg.rs
+++ b/crates/ra_assists/src/assists/remove_dbg.rs
@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use crate::{Assist, AssistCtx, AssistId};
 use hir::db::HirDatabase;
 use ra_syntax::{
diff --git a/crates/ra_assists/src/assists/replace_if_let_with_match.rs b/crates/ra_assists/src/assists/replace_if_let_with_match.rs
index 401835c57..749ff338a 100644
--- a/crates/ra_assists/src/assists/replace_if_let_with_match.rs
+++ b/crates/ra_assists/src/assists/replace_if_let_with_match.rs
@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use format_buf::format;
 use hir::db::HirDatabase;
 use ra_fmt::extract_trivial_expression;
diff --git a/crates/ra_assists/src/assists/split_import.rs b/crates/ra_assists/src/assists/split_import.rs
index 2c1edddb9..fe3e64af5 100644
--- a/crates/ra_assists/src/assists/split_import.rs
+++ b/crates/ra_assists/src/assists/split_import.rs
@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use std::iter::successors;
 
 use hir::db::HirDatabase;
@@ -49,13 +51,13 @@ mod tests {
     fn split_import_works_with_trees() {
         check_assist(
             split_import,
-            "use algo:<|>:visitor::{Visitor, visit}",
-            "use algo::{<|>visitor::{Visitor, visit}}",
+            "use crate:<|>:db::{RootDatabase, FileSymbol}",
+            "use crate::{<|>db::{RootDatabase, FileSymbol}}",
         )
     }
 
     #[test]
     fn split_import_target() {
-        check_assist_target(split_import, "use algo::<|>visitor::{Visitor, visit}", "::");
+        check_assist_target(split_import, "use crate::<|>db::{RootDatabase, FileSymbol}", "::");
     }
 }
diff --git a/crates/ra_assists/src/ast_editor.rs b/crates/ra_assists/src/ast_editor.rs
deleted file mode 100644
index 2a685f26e..000000000
--- a/crates/ra_assists/src/ast_editor.rs
+++ /dev/null
@@ -1,315 +0,0 @@
-use std::{iter, ops::RangeInclusive};
-
-use arrayvec::ArrayVec;
-use rustc_hash::FxHashMap;
-
-use ra_fmt::leading_indent;
-use ra_syntax::{
-    algo,
-    ast::{self, TypeBoundsOwner},
-    AstNode, Direction, InsertPosition, SyntaxElement,
-    SyntaxKind::*,
-    T,
-};
-use ra_text_edit::TextEditBuilder;
-
-pub struct AstEditor<N: AstNode> {
-    original_ast: N,
-    ast: N,
-}
-
-impl<N: AstNode> AstEditor<N> {
-    pub fn new(node: N) -> AstEditor<N>
-    where
-        N: Clone,
-    {
-        AstEditor { original_ast: node.clone(), ast: node }
-    }
-
-    pub fn into_text_edit(self, builder: &mut TextEditBuilder) {
-        for (from, to) in algo::diff(&self.original_ast.syntax(), self.ast().syntax()) {
-            builder.replace(from.text_range(), to.to_string())
-        }
-    }
-
-    pub fn ast(&self) -> &N {
-        &self.ast
-    }
-
-    pub fn replace_descendants<T: AstNode>(
-        &mut self,
-        replacement_map: impl Iterator<Item = (T, T)>,
-    ) -> &mut Self {
-        let map = replacement_map
-            .map(|(from, to)| (from.syntax().clone().into(), to.syntax().clone().into()))
-            .collect::<FxHashMap<_, _>>();
-        let new_syntax = algo::replace_descendants(self.ast.syntax(), &map);
-        self.ast = N::cast(new_syntax).unwrap();
-        self
-    }
-
-    #[must_use]
-    fn insert_children(
-        &self,
-        position: InsertPosition<SyntaxElement>,
-        mut to_insert: impl Iterator<Item = SyntaxElement>,
-    ) -> N {
-        let new_syntax = algo::insert_children(self.ast().syntax(), position, &mut to_insert);
-        N::cast(new_syntax).unwrap()
-    }
-
-    #[must_use]
-    fn replace_children(
-        &self,
-        to_delete: RangeInclusive<SyntaxElement>,
-        mut to_insert: impl Iterator<Item = SyntaxElement>,
-    ) -> N {
-        let new_syntax = algo::replace_children(self.ast().syntax(), to_delete, &mut to_insert);
-        N::cast(new_syntax).unwrap()
-    }
-
-    fn do_make_multiline(&mut self) {
-        let l_curly =
-            match self.ast().syntax().children_with_tokens().find(|it| it.kind() == T!['{']) {
-                Some(it) => it,
-                None => return,
-            };
-        let sibling = match l_curly.next_sibling_or_token() {
-            Some(it) => it,
-            None => return,
-        };
-        let existing_ws = match sibling.as_token() {
-            None => None,
-            Some(tok) if tok.kind() != WHITESPACE => None,
-            Some(ws) => {
-                if ws.text().contains('\n') {
-                    return;
-                }
-                Some(ws.clone())
-            }
-        };
-
-        let indent = leading_indent(self.ast().syntax()).unwrap_or("".into());
-        let ws = tokens::WsBuilder::new(&format!("\n{}", indent));
-        let to_insert = iter::once(ws.ws().into());
-        self.ast = match existing_ws {
-            None => self.insert_children(InsertPosition::After(l_curly), to_insert),
-            Some(ws) => {
-                self.replace_children(RangeInclusive::new(ws.clone().into(), ws.into()), to_insert)
-            }
-        };
-    }
-}
-
-impl AstEditor<ast::RecordFieldList> {
-    pub fn append_field(&mut self, field: &ast::RecordField) {
-        self.insert_field(InsertPosition::Last, field)
-    }
-
-    pub fn insert_field(
-        &mut self,
-        position: InsertPosition<&'_ ast::RecordField>,
-        field: &ast::RecordField,
-    ) {
-        let is_multiline = self.ast().syntax().text().contains_char('\n');
-        let ws;
-        let space = if is_multiline {
-            ws = tokens::WsBuilder::new(&format!(
-                "\n{}    ",
-                leading_indent(self.ast().syntax()).unwrap_or("".into())
-            ));
-            ws.ws()
-        } else {
-            tokens::single_space()
-        };
-
-        let mut to_insert: ArrayVec<[SyntaxElement; 4]> = ArrayVec::new();
-        to_insert.push(space.into());
-        to_insert.push(field.syntax().clone().into());
-        to_insert.push(tokens::comma().into());
-
-        macro_rules! after_l_curly {
-            () => {{
-                let anchor = match self.l_curly() {
-                    Some(it) => it,
-                    None => return,
-                };
-                InsertPosition::After(anchor)
-            }};
-        }
-
-        macro_rules! after_field {
-            ($anchor:expr) => {
-                if let Some(comma) = $anchor
-                    .syntax()
-                    .siblings_with_tokens(Direction::Next)
-                    .find(|it| it.kind() == T![,])
-                {
-                    InsertPosition::After(comma)
-                } else {
-                    to_insert.insert(0, tokens::comma().into());
-                    InsertPosition::After($anchor.syntax().clone().into())
-                }
-            };
-        };
-
-        let position = match position {
-            InsertPosition::First => after_l_curly!(),
-            InsertPosition::Last => {
-                if !is_multiline {
-                    // don't insert comma before curly
-                    to_insert.pop();
-                }
-                match self.ast().fields().last() {
-                    Some(it) => after_field!(it),
-                    None => after_l_curly!(),
-                }
-            }
-            InsertPosition::Before(anchor) => {
-                InsertPosition::Before(anchor.syntax().clone().into())
-            }
-            InsertPosition::After(anchor) => after_field!(anchor),
-        };
-
-        self.ast = self.insert_children(position, to_insert.iter().cloned());
-    }
-
-    fn l_curly(&self) -> Option<SyntaxElement> {
-        self.ast().syntax().children_with_tokens().find(|it| it.kind() == T!['{'])
-    }
-}
-
-impl AstEditor<ast::ItemList> {
-    pub fn append_items(&mut self, items: impl Iterator<Item = ast::ImplItem>) {
-        if !self.ast().syntax().text().contains_char('\n') {
-            self.do_make_multiline();
-        }
-        items.for_each(|it| self.append_item(it));
-    }
-
-    pub fn append_item(&mut self, item: ast::ImplItem) {
-        let (indent, position) = match self.ast().impl_items().last() {
-            Some(it) => (
-                leading_indent(it.syntax()).unwrap_or_default().to_string(),
-                InsertPosition::After(it.syntax().clone().into()),
-            ),
-            None => match self.l_curly() {
-                Some(it) => (
-                    "    ".to_string() + &leading_indent(self.ast().syntax()).unwrap_or_default(),
-                    InsertPosition::After(it),
-                ),
-                None => return,
-            },
-        };
-        let ws = tokens::WsBuilder::new(&format!("\n{}", indent));
-        let to_insert: ArrayVec<[SyntaxElement; 2]> =
-            [ws.ws().into(), item.syntax().clone().into()].into();
-        self.ast = self.insert_children(position, to_insert.into_iter());
-    }
-
-    fn l_curly(&self) -> Option<SyntaxElement> {
-        self.ast().syntax().children_with_tokens().find(|it| it.kind() == T!['{'])
-    }
-}
-
-impl AstEditor<ast::ImplItem> {
-    pub fn strip_attrs_and_docs(&mut self) {
-        while let Some(start) = self
-            .ast()
-            .syntax()
-            .children_with_tokens()
-            .find(|it| it.kind() == ATTR || it.kind() == COMMENT)
-        {
-            let end = match &start.next_sibling_or_token() {
-                Some(el) if el.kind() == WHITESPACE => el.clone(),
-                Some(_) | None => start.clone(),
-            };
-            self.ast = self.replace_children(RangeInclusive::new(start, end), iter::empty());
-        }
-    }
-}
-
-impl AstEditor<ast::FnDef> {
-    pub fn set_body(&mut self, body: &ast::Block) {
-        let mut to_insert: ArrayVec<[SyntaxElement; 2]> = ArrayVec::new();
-        let old_body_or_semi: SyntaxElement = if let Some(old_body) = self.ast().body() {
-            old_body.syntax().clone().into()
-        } else if let Some(semi) = self.ast().semicolon_token() {
-            to_insert.push(tokens::single_space().into());
-            semi.into()
-        } else {
-            to_insert.push(tokens::single_space().into());
-            to_insert.push(body.syntax().clone().into());
-            self.ast = self.insert_children(InsertPosition::Last, to_insert.into_iter());
-            return;
-        };
-        to_insert.push(body.syntax().clone().into());
-        let replace_range = RangeInclusive::new(old_body_or_semi.clone(), old_body_or_semi);
-        self.ast = self.replace_children(replace_range, to_insert.into_iter())
-    }
-}
-
-impl AstEditor<ast::TypeParam> {
-    pub fn remove_bounds(&mut self) -> &mut Self {
-        let colon = match self.ast.colon_token() {
-            Some(it) => it,
-            None => return self,
-        };
-        let end = match self.ast.type_bound_list() {
-            Some(it) => it.syntax().clone().into(),
-            None => colon.clone().into(),
-        };
-        self.ast = self.replace_children(RangeInclusive::new(colon.into(), end), iter::empty());
-        self
-    }
-}
-
-mod tokens {
-    use once_cell::sync::Lazy;
-    use ra_syntax::{AstNode, Parse, SourceFile, SyntaxKind::*, SyntaxToken, T};
-
-    static SOURCE_FILE: Lazy<Parse<SourceFile>> = Lazy::new(|| SourceFile::parse(",\n; ;"));
-
-    pub(crate) fn comma() -> SyntaxToken {
-        SOURCE_FILE
-            .tree()
-            .syntax()
-            .descendants_with_tokens()
-            .filter_map(|it| it.into_token())
-            .find(|it| it.kind() == T![,])
-            .unwrap()
-    }
-
-    pub(crate) fn single_space() -> SyntaxToken {
-        SOURCE_FILE
-            .tree()
-            .syntax()
-            .descendants_with_tokens()
-            .filter_map(|it| it.into_token())
-            .find(|it| it.kind() == WHITESPACE && it.text().as_str() == " ")
-            .unwrap()
-    }
-
-    #[allow(unused)]
-    pub(crate) fn single_newline() -> SyntaxToken {
-        SOURCE_FILE
-            .tree()
-            .syntax()
-            .descendants_with_tokens()
-            .filter_map(|it| it.into_token())
-            .find(|it| it.kind() == WHITESPACE && it.text().as_str() == "\n")
-            .unwrap()
-    }
-
-    pub(crate) struct WsBuilder(SourceFile);
-
-    impl WsBuilder {
-        pub(crate) fn new(text: &str) -> WsBuilder {
-            WsBuilder(SourceFile::parse(text).ok().unwrap())
-        }
-        pub(crate) fn ws(&self) -> SyntaxToken {
-            self.0.syntax().first_child_or_token().unwrap().into_token().unwrap()
-        }
-    }
-
-}
diff --git a/crates/ra_assists/src/lib.rs b/crates/ra_assists/src/lib.rs
index 3ca3320f7..d2376c475 100644
--- a/crates/ra_assists/src/lib.rs
+++ b/crates/ra_assists/src/lib.rs
@@ -7,7 +7,6 @@
 
 mod assist_ctx;
 mod marks;
-pub mod ast_editor;
 
 use hir::db::HirDatabase;
 use itertools::Itertools;
@@ -93,6 +92,7 @@ mod assists {
     mod add_derive;
     mod add_explicit_type;
     mod add_impl;
+    mod apply_demorgan;
     mod flip_comma;
     mod flip_binexpr;
     mod change_visibility;
@@ -114,6 +114,7 @@ mod assists {
             add_derive::add_derive,
             add_explicit_type::add_explicit_type,
             add_impl::add_impl,
+            apply_demorgan::apply_demorgan,
             change_visibility::change_visibility,
             fill_match_arms::fill_match_arms,
             merge_match_arms::merge_match_arms,
diff --git a/crates/ra_assists/src/marks.rs b/crates/ra_assists/src/marks.rs
index a29f9f658..c20e4db9e 100644
--- a/crates/ra_assists/src/marks.rs
+++ b/crates/ra_assists/src/marks.rs
@@ -1,3 +1,5 @@
+//! See test_utils/src/marks.rs
+
 test_utils::marks!(
     introduce_var_in_comment_is_not_applicable
     test_introduce_var_expr_stmt