Add (Rule)Node::reconstruct that recreates the source code

crates/codegen/parser/runtime/src/cst.rs

@@ -51,20 +51,42 @@ impl Node {
         Cursor::new(self.clone(), text_offset)
     }
 
+    /// Reconstructs the original source code from the parse tree.
+    pub fn reconstruct(self) -> String {
+        match self {
+            Self::Rule(rule) => rule.reconstruct(),
+            Self::Token(token) => token.text.clone(),
+        }
+    }
+
     pub fn as_rule(&self) -> Option<&Rc<RuleNode>> {
         match self {
             Self::Rule(node) => Some(node),
             _ => None,
         }
     }
 
+    pub fn into_rule(self) -> Option<Rc<RuleNode>> {
+        match self {
+            Self::Rule(node) => Some(node),
+            _ => None,
+        }
+    }
+
     pub fn as_token(&self) -> Option<&Rc<TokenNode>> {
         match self {
             Self::Token(node) => Some(node),
             _ => None,
         }
     }
 
+    pub fn into_token(self) -> Option<Rc<TokenNode>> {
+        match self {
+            Self::Token(node) => Some(node),
+            _ => None,
+        }
+    }
+
     pub fn as_token_with_kind(&self, kinds: &[TokenKind]) -> Option<&Rc<TokenNode>> {
         self.as_token_matching(|token| kinds.contains(&token.kind))
     }
@@ -111,4 +133,16 @@ impl RuleNode {
     pub fn cursor_with_offset(self: Rc<Self>, text_offset: TextIndex) -> Cursor {
         Cursor::new(Node::Rule(self), text_offset)
     }
+
+    /// Reconstructs the original source code from the parse tree.
+    pub fn reconstruct(self: Rc<Self>) -> String {
+        let acc = String::with_capacity(self.text_len.utf8);
+
+        self.cursor_with_offset(TextIndex::ZERO)
+            .filter_map(Node::into_token)
+            .fold(acc, |mut acc, token| {
+                acc.push_str(&token.text);
+                acc
+            })
+    }
 }

crates/codegen/parser/runtime/src/text_index.rs

@@ -12,6 +12,15 @@ pub struct TextIndex {
     pub char: usize,
 }
 
+impl TextIndex {
+    /// Shorthand for `TextIndex { utf8: 0, utf16: 0, char: 0 }`.
+    pub const ZERO: TextIndex = TextIndex {
+        utf8: 0,
+        utf16: 0,
+        char: 0,
+    };
+}
+
 impl PartialOrd for TextIndex {
     fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
         self.utf8.partial_cmp(&other.utf8)

crates/solidity/outputs/cargo/tests/src/doc_examples/simple_contract.rs

@@ -14,12 +14,13 @@ fn simple_contract() -> Result<()> {
 
     let parse_tree = parse_output.tree();
 
-    let children = if let Node::Rule(rule) = &parse_tree {
+    let rule = if let Node::Rule(rule) = parse_tree {
         assert_eq!(rule.kind, RuleKind::ContractDefinition);
-        &rule.children
+        rule
     } else {
         panic!("Unexpected parse_tree");
     };
+    let children = &rule.children;
 
     assert_eq!(children.len(), 6);
 
@@ -30,5 +31,7 @@ fn simple_contract() -> Result<()> {
     assert!(matches!(&children[4], Node::Token(token) if token.kind == TokenKind::OpenBrace));
     assert!(matches!(&children[5], Node::Token(token) if token.kind == TokenKind::CloseBrace));
 
+    assert_eq!(rule.reconstruct(), "contract Foo {}");
+
     return Ok(());
 }