1 files changed, 105 insertions, 0 deletions

diff --git a/crates/syntax/src/ast/edit_in_place.rs b/crates/syntax/src/ast/edit_in_place.rs
new file mode 100644
index 000000000..06cde591d
--- /dev/null
+++ b/crates/syntax/src/ast/edit_in_place.rs
@@ -0,0 +1,105 @@
+//! Structural editing for ast.
+
+use std::iter::empty;
+
+use ast::{edit::AstNodeEdit, make, GenericParamsOwner, WhereClause};
+use parser::T;
+
+use crate::{
+    ast,
+    ted::{self, Position},
+    AstNode, Direction, SyntaxKind,
+};
+
+use super::NameOwner;
+
+pub trait GenericParamsOwnerEdit: ast::GenericParamsOwner + AstNodeEdit {
+    fn get_or_create_where_clause(&self) -> ast::WhereClause;
+}
+
+impl GenericParamsOwnerEdit for ast::Fn {
+    fn get_or_create_where_clause(&self) -> WhereClause {
+        if self.where_clause().is_none() {
+            let position = if let Some(ty) = self.ret_type() {
+                Position::after(ty.syntax().clone())
+            } else if let Some(param_list) = self.param_list() {
+                Position::after(param_list.syntax().clone())
+            } else {
+                Position::last_child_of(self.syntax().clone())
+            };
+            create_where_clause(position)
+        }
+        self.where_clause().unwrap()
+    }
+}
+
+impl GenericParamsOwnerEdit for ast::Impl {
+    fn get_or_create_where_clause(&self) -> WhereClause {
+        if self.where_clause().is_none() {
+            let position = if let Some(ty) = self.self_ty() {
+                Position::after(ty.syntax().clone())
+            } else {
+                Position::last_child_of(self.syntax().clone())
+            };
+            create_where_clause(position)
+        }
+        self.where_clause().unwrap()
+    }
+}
+impl GenericParamsOwnerEdit for ast::Struct {
+    fn get_or_create_where_clause(&self) -> WhereClause {
+        if self.where_clause().is_none() {
+            let tfl = self.field_list().and_then(|fl| match fl {
+                ast::FieldList::RecordFieldList(_) => None,
+                ast::FieldList::TupleFieldList(it) => Some(it),
+            });
+            let position = if let Some(tfl) = tfl {
+                Position::after(tfl.syntax().clone())
+            } else if let Some(gpl) = self.generic_param_list() {
+                Position::after(gpl.syntax().clone())
+            } else if let Some(name) = self.name() {
+                Position::after(name.syntax().clone())
+            } else {
+                Position::last_child_of(self.syntax().clone())
+            };
+            create_where_clause(position)
+        }
+        self.where_clause().unwrap()
+    }
+}
+
+fn create_where_clause(position: Position) {
+    let elements = vec![
+        make::tokens::single_space().into(),
+        make::where_clause(empty()).clone_for_update().syntax().clone().into(),
+    ];
+    ted::insert_all(position, elements);
+}
+
+impl ast::WhereClause {
+    pub fn add_predicate(&self, predicate: ast::WherePred) {
+        if let Some(pred) = self.predicates().last() {
+            if !pred.syntax().siblings_with_tokens(Direction::Next).any(|it| it.kind() == T![,]) {
+                ted::append_child(self.syntax().clone(), make::token(T![,]));
+            }
+        }
+        if self.syntax().children_with_tokens().last().map(|it| it.kind())
+            != Some(SyntaxKind::WHITESPACE)
+        {
+            ted::append_child(self.syntax().clone(), make::tokens::single_space());
+        }
+        ted::append_child(self.syntax().clone(), predicate.syntax().clone())
+    }
+}
+
+impl ast::TypeBoundList {
+    pub fn remove(&self) {
+        if let Some(colon) =
+            self.syntax().siblings_with_tokens(Direction::Prev).find(|it| it.kind() == T![:])
+        {
+            ted::remove_all(colon..=self.syntax().clone().into())
+        } else {
+            ted::remove(self.syntax().clone())
+        }
+    }
+}