Add inlay hint for exclusive ranges

Adds an inlay hint containing a '<' character to exclusive range expressions and patterns that specify an upper bound.

crates/syntax/src/ast/node_ext.rs

@@ -14,6 +14,8 @@ use crate::{
     ted, NodeOrToken, SmolStr, SyntaxElement, SyntaxToken, TokenText, T,
 };
 
+use super::{RangeItem, RangeOp};
+
 impl ast::Lifetime {
     pub fn text(&self) -> TokenText<'_> {
         text_of_first_token(self.syntax())
@@ -875,8 +877,10 @@ impl ast::Module {
     }
 }
 
-impl ast::RangePat {
-    pub fn start(&self) -> Option<ast::Pat> {
+impl RangeItem for ast::RangePat {
+    type Bound = ast::Pat;
+
+    fn start(&self) -> Option<ast::Pat> {
         self.syntax()
             .children_with_tokens()
             .take_while(|it| !(it.kind() == T![..] || it.kind() == T![..=]))
@@ -884,13 +888,37 @@ impl ast::RangePat {
             .find_map(ast::Pat::cast)
     }
 
-    pub fn end(&self) -> Option<ast::Pat> {
+    fn end(&self) -> Option<ast::Pat> {
         self.syntax()
             .children_with_tokens()
             .skip_while(|it| !(it.kind() == T![..] || it.kind() == T![..=]))
             .filter_map(|it| it.into_node())
             .find_map(ast::Pat::cast)
     }
+
+    fn op_token(&self) -> Option<SyntaxToken> {
+        self.syntax().children_with_tokens().find_map(|it| {
+            let token = it.into_token()?;
+
+            match token.kind() {
+                T![..] => Some(token),
+                T![..=] => Some(token),
+                _ => None,
+            }
+        })
+    }
+
+    fn op_kind(&self) -> Option<RangeOp> {
+        self.syntax().children_with_tokens().find_map(|it| {
+            let token = it.into_token()?;
+
+            match token.kind() {
+                T![..] => Some(RangeOp::Exclusive),
+                T![..=] => Some(RangeOp::Inclusive),
+                _ => None,
+            }
+        })
+    }
 }
 
 impl ast::TokenTree {