Refactor Symbol and Keyword as nodes (#67)

Refactor the previous implementation of `Symbol`/`Keyword` handling to
treat them as first-class nodes in the build configuration.

`Keyword` and `Symbol` represent identifiers (interned strings), not
traditional AST nodes. However, the C parser defines them in
`rbs_node_type` (as `RBS_KEYWORD` and `RBS_AST_SYMBOL`) and treats them
as nodes (`rbs_node_t*`) in many contexts (lists, hashes).

Instead of manually defining `RBSSymbol`/`RBSKeyword` structs, we now
inject them into the `config.yml` node list in `build.rs`. This allows
them to be generated as `SymbolNode`/`KeywordNode` variants in the
`Node` enum, enabling polymorphic handling (in Node lists and Hashes)

Author: alexcrocha

rust/ruby-rbs/build.rs

@@ -37,6 +37,22 @@ fn main() -> Result<(), Box<dyn Error>> {
     let config_file = File::open(&config_path)?;
     let mut config: Config = serde_yaml::from_reader(config_file)?;
 
+    // Keyword and Symbol represent identifiers (interned strings), not traditional AST nodes.
+    // However, the C parser defines them in `rbs_node_type` (RBS_KEYWORD, RBS_AST_SYMBOL) and
+    // treats them as nodes (rbs_node_t*) in many contexts (lists, hashes).
+    // We inject them into the config so they are generated as structs matching the Node pattern,
+    // allowing them to be wrapped in the Node enum and handled uniformly in Rust.
+    config.nodes.push(Node {
+        name: "RBS::Keyword".to_string(),
+        rust_name: "KeywordNode".to_string(),
+        fields: None,
+    });
+    config.nodes.push(Node {
+        name: "RBS::AST::Symbol".to_string(),
+        rust_name: "SymbolNode".to_string(),
+        fields: None,
+    });
+
     config.nodes.sort_by(|a, b| a.name.cmp(&b.name));
     generate(&config)?;
 
@@ -148,10 +164,10 @@ fn generate(config: &Config) -> Result<(), Box<dyn Error>> {
                         writeln!(file, "    }}")?;
                     }
                     "rbs_ast_symbol" => {
-                        writeln!(file, "    pub fn {}(&self) -> RBSSymbol {{", field.name)?;
+                        writeln!(file, "    pub fn {}(&self) -> SymbolNode {{", field.name)?;
                         writeln!(
                             file,
-                            "        RBSSymbol::new(unsafe {{ (*self.pointer).{} }}, self.parser)",
+                            "        SymbolNode {{ parser: self.parser, pointer: unsafe {{ (*self.pointer).{} }} }}",
                             field.c_name()
                         )?;
                         writeln!(file, "    }}")?;
@@ -212,10 +228,10 @@ fn generate(config: &Config) -> Result<(), Box<dyn Error>> {
                         writeln!(file, "    }}")?;
                     }
                     "rbs_keyword" => {
-                        writeln!(file, "    pub fn {}(&self) -> RBSKeyword {{", field.name)?;
+                        writeln!(file, "    pub fn {}(&self) -> KeywordNode {{", field.name)?;
                         writeln!(
                             file,
-                            "        RBSKeyword::new(self.parser, unsafe {{ (*self.pointer).{} }})",
+                            "        KeywordNode {{ parser: self.parser, pointer: unsafe {{ (*self.pointer).{} }} }}",
                             field.c_name()
                         )?;
                         writeln!(file, "    }}")?;

rust/ruby-rbs/src/lib.rs

@@ -169,16 +169,7 @@ impl RBSString {
     }
 }
 
-pub struct RBSSymbol {
-    pointer: *const rbs_ast_symbol_t,
-    parser: *mut rbs_parser_t,
-}
-
-impl RBSSymbol {
-    pub fn new(pointer: *const rbs_ast_symbol_t, parser: *mut rbs_parser_t) -> Self {
-        Self { pointer, parser }
-    }
-
+impl SymbolNode {
     pub fn name(&self) -> &[u8] {
         unsafe {
             let constant_ptr = rbs_constant_pool_id_to_constant(
@@ -195,16 +186,7 @@ impl RBSSymbol {
     }
 }
 
-pub struct RBSKeyword {
-    parser: *mut rbs_parser_t,
-    pointer: *const rbs_keyword,
-}
-
-impl RBSKeyword {
-    pub fn new(parser: *mut rbs_parser_t, pointer: *const rbs_keyword) -> Self {
-        Self { parser, pointer }
-    }
-
+impl KeywordNode {
     pub fn name(&self) -> &[u8] {
         unsafe {
             let constant_ptr = rbs_constant_pool_id_to_constant(