Merge #8280

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

In rust-analyzer/rowan#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 rust-analyzer/rowan#100 (comment)

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

Author: bors[bot]

Cargo.lock

@@ -283,7 +283,7 @@ fn macro_arg_text(db: &dyn AstDatabase, id: MacroCallId) -> Option<GreenNode> {
     };
     let loc = db.lookup_intern_macro(id);
     let arg = loc.kind.arg(db)?;
-    Some(arg.green())
+    Some(arg.green().into())
 }
 
 fn macro_def(db: &dyn AstDatabase, id: MacroDefId) -> Option<Arc<TokenExpander>> {

crates/hir_expand/src/db.rs

@@ -13,7 +13,7 @@ doctest = false
 [dependencies]
 cov-mark = { version = "1.1", features = ["thread-local"] }
 itertools = "0.10.0"
-rowan = "=0.13.0-pre.3"
+rowan = "=0.13.0-pre.5"
 rustc_lexer = { version = "716.0.0", package = "rustc-ap-rustc_lexer" }
 rustc-hash = "1.1.0"
 arrayvec = "0.7"

crates/syntax/Cargo.toml

@@ -555,7 +555,7 @@ impl SyntaxRewriter<'_> {
 
 fn element_to_green(element: SyntaxElement) -> NodeOrToken<rowan::GreenNode, rowan::GreenToken> {
     match element {
-        NodeOrToken::Node(it) => NodeOrToken::Node(it.green()),
+        NodeOrToken::Node(it) => NodeOrToken::Node(it.green().into_owned()),
         NodeOrToken::Token(it) => NodeOrToken::Token(it.green().to_owned()),
     }
 }

crates/syntax/src/algo.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 {

crates/syntax/src/ast/make.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(),

crates/syntax/src/ast/node_ext.rs

@@ -2,75 +2,93 @@
 
 use std::{cmp::Ordering, fmt, ops};
 
-pub struct TokenText(pub(crate) rowan::GreenToken);
+use rowan::GreenToken;
+
+pub struct TokenText<'a>(pub(crate) Repr<'a>);
+
+pub(crate) enum Repr<'a> {
+    Borrowed(&'a str),
+    Owned(GreenToken),
+}
+
+impl<'a> TokenText<'a> {
+    pub(crate) fn borrowed(text: &'a str) -> Self {
+        TokenText(Repr::Borrowed(text))
+    }
+
+    pub(crate) fn owned(green: GreenToken) -> Self {
+        TokenText(Repr::Owned(green))
+    }
 
-impl TokenText {
     pub fn as_str(&self) -> &str {
-        self.0.text()
+        match self.0 {
+            Repr::Borrowed(it) => it,
+            Repr::Owned(ref green) => green.text(),
+        }
     }
 }
 
-impl ops::Deref for TokenText {
+impl ops::Deref for TokenText<'_> {
     type Target = str;
 
     fn deref(&self) -> &str {
         self.as_str()
     }
 }
-impl AsRef<str> for TokenText {
+impl AsRef<str> for TokenText<'_> {
     fn as_ref(&self) -> &str {
         self.as_str()
     }
 }
 
-impl From<TokenText> for String {
+impl From<TokenText<'_>> for String {
     fn from(token_text: TokenText) -> Self {
         token_text.as_str().into()
     }
 }
 
-impl PartialEq<&'_ str> for TokenText {
+impl PartialEq<&'_ str> for TokenText<'_> {
     fn eq(&self, other: &&str) -> bool {
         self.as_str() == *other
     }
 }
-impl PartialEq<TokenText> for &'_ str {
+impl PartialEq<TokenText<'_>> for &'_ str {
     fn eq(&self, other: &TokenText) -> bool {
         other == self
     }
 }
-impl PartialEq<String> for TokenText {
+impl PartialEq<String> for TokenText<'_> {
     fn eq(&self, other: &String) -> bool {
         self.as_str() == other.as_str()
     }
 }
-impl PartialEq<TokenText> for String {
+impl PartialEq<TokenText<'_>> for String {
     fn eq(&self, other: &TokenText) -> bool {
         other == self
     }
 }
-impl PartialEq for TokenText {
+impl PartialEq for TokenText<'_> {
     fn eq(&self, other: &TokenText) -> bool {
         self.as_str() == other.as_str()
     }
 }
-impl Eq for TokenText {}
-impl Ord for TokenText {
+impl Eq for TokenText<'_> {}
+impl Ord for TokenText<'_> {
     fn cmp(&self, other: &Self) -> Ordering {
         self.as_str().cmp(other.as_str())
     }
 }
-impl PartialOrd for TokenText {
+impl PartialOrd for TokenText<'_> {
     fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
         Some(self.cmp(other))
     }
 }
-impl fmt::Display for TokenText {
+impl fmt::Display for TokenText<'_> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         fmt::Display::fmt(self.as_str(), f)
     }
 }
-impl fmt::Debug for TokenText {
+impl fmt::Debug for TokenText<'_> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         fmt::Debug::fmt(self.as_str(), f)
     }