Merge #8280

8280: Borrow text of immutable syntax node r=iDawer a=iDawer

In https://github.com/rust-analyzer/rowan/pull/101 `rowan::SyntaxNode::green` returns `Cow<'_, GreenNodeData>`. It returns borrow of green node of immutable syntax tree node.
Using this we can return borrowed text from `ast::Name::text`.

~~However now it allocates in case of mutable syntax trees.~~ (see next comment)

The idea comes from https://github.com/rust-analyzer/rowan/pull/100#issuecomment-809330325

Co-authored-by: Dawer <[email protected]>

2 files changed, 16 insertions, 11 deletions

diff --git a/crates/syntax/src/ast/make.rs b/crates/syntax/src/ast/make.rs
index 42da09606..4bcea28cc 100644
--- a/crates/syntax/src/ast/make.rs
+++ b/crates/syntax/src/ast/make.rs
@@ -572,7 +572,7 @@ fn ast_from_text<N: AstNode>(text: &str) -> N {
 }
 
 fn unroot(n: SyntaxNode) -> SyntaxNode {
-    SyntaxNode::new_root(n.green())
+    SyntaxNode::new_root(n.green().into())
 }
 
 pub mod tokens {
diff --git a/crates/syntax/src/ast/node_ext.rs b/crates/syntax/src/ast/node_ext.rs
index 492fbc4a0..bef49238f 100644
--- a/crates/syntax/src/ast/node_ext.rs
+++ b/crates/syntax/src/ast/node_ext.rs
@@ -1,30 +1,31 @@
 //! Various extension methods to ast Nodes, which are hard to code-generate.
 //! Extensions for various expressions live in a sibling `expr_extensions` module.
 
-use std::{fmt, iter::successors};
+use std::{borrow::Cow, fmt, iter::successors};
 
 use itertools::Itertools;
 use parser::SyntaxKind;
+use rowan::{GreenNodeData, GreenTokenData};
 
 use crate::{
     ast::{self, support, AstNode, AstToken, AttrsOwner, NameOwner, SyntaxNode},
-    SmolStr, SyntaxElement, SyntaxToken, TokenText, T,
+    NodeOrToken, SmolStr, SyntaxElement, SyntaxToken, TokenText, T,
 };
 
 impl ast::Lifetime {
-    pub fn text(&self) -> TokenText {
+    pub fn text(&self) -> TokenText<'_> {
         text_of_first_token(self.syntax())
     }
 }
 
 impl ast::Name {
-    pub fn text(&self) -> TokenText {
+    pub fn text(&self) -> TokenText<'_> {
         text_of_first_token(self.syntax())
     }
 }
 
 impl ast::NameRef {
-    pub fn text(&self) -> TokenText {
+    pub fn text(&self) -> TokenText<'_> {
         text_of_first_token(self.syntax())
     }
 
@@ -33,11 +34,15 @@ impl ast::NameRef {
     }
 }
 
-fn text_of_first_token(node: &SyntaxNode) -> TokenText {
-    let first_token =
-        node.green().children().next().and_then(|it| it.into_token()).unwrap().to_owned();
+fn text_of_first_token(node: &SyntaxNode) -> TokenText<'_> {
+    fn first_token(green_ref: &GreenNodeData) -> &GreenTokenData {
+        green_ref.children().next().and_then(NodeOrToken::into_token).unwrap()
+    }
 
-    TokenText(first_token)
+    match node.green() {
+        Cow::Borrowed(green_ref) => TokenText::borrowed(first_token(green_ref).text()),
+        Cow::Owned(green) => TokenText::owned(first_token(&green).to_owned()),
+    }
 }
 
 #[derive(Debug, PartialEq, Eq, Clone)]
@@ -412,7 +417,7 @@ impl fmt::Display for NameOrNameRef {
 }
 
 impl NameOrNameRef {
-    pub fn text(&self) -> TokenText {
+    pub fn text(&self) -> TokenText<'_> {
         match self {
             NameOrNameRef::Name(name) => name.text(),
             NameOrNameRef::NameRef(name_ref) => name_ref.text(),