cl-ast: Add Fold and Visit traits, to more easily map or collect nodes in the AST

typeck.rs: Since this is apparently my testbed now, add a new mode.
TODO: replace the main `conlang` binary with this, since it's so much better.

cl-repl/examples/typeck.rs

@@ -1,3 +1,7 @@
+use cl_ast::{
+    ast_visitor::fold::Fold,
+    desugar::{squash_groups::SquashGroups, while_else::WhileElseDesugar},
+};
 use cl_lexer::Lexer;
 use cl_parser::Parser;
 use cl_repl::repline::{error::Error as RlError, Repline};
@@ -33,6 +37,7 @@ fn main() -> Result<(), Box<dyn Error>> {
             Err(e)?
         }
     };
+
     unsafe { TREES.push(code) }.collect_in_root(&mut prj)?;
 
     main_menu(&mut prj)
@@ -81,6 +86,7 @@ fn main_menu(prj: &mut Project) -> Result<(), Box<dyn Error>> {
             "l" | "list" => list_types(prj),
             "q" | "query" => query_type_expression(prj),
             "r" | "resolve" => resolve_all(prj),
+            "d" | "desugar" => live_desugar(),
             "h" | "help" => {
                 println!(
                     "Valid commands are:
@@ -88,6 +94,7 @@ fn main_menu(prj: &mut Project) -> Result<(), Box<dyn Error>> {
     list    (l): List all known types
     query   (q): Query the type system
     resolve (r): Perform type resolution
+    desugar (d): WIP: Test the experimental desugaring passes
     help    (h): Print this list
     exit    (e): Exit the program"
                 );
@@ -105,7 +112,7 @@ fn enter_code(prj: &mut Project) -> Result<(), Box<dyn Error>> {
             return Ok(Response::Break);
         }
         let code = Parser::new(Lexer::new(line)).file()?;
-
+        let code = WhileElseDesugar.fold_file(code);
         // Safety: this is totally unsafe
         unsafe { TREES.push(code) }.collect_in_root(prj)?;
 
@@ -113,6 +120,21 @@ fn enter_code(prj: &mut Project) -> Result<(), Box<dyn Error>> {
     })
 }
 
+fn live_desugar() -> Result<(), Box<dyn Error>> {
+    read_and(C_RESV, "se>", |line| {
+        let code = Parser::new(Lexer::new(line)).stmt()?;
+        println!("Raw, as parsed:\n{C_LISTING}{code}\x1b[0m");
+
+        let code = SquashGroups.fold_stmt(code);
+        println!("SquashGroups\n{C_LISTING}{code}\x1b[0m");
+
+        let code = WhileElseDesugar.fold_stmt(code);
+        println!("WhileElseDesugar\n{C_LISTING}{code}\x1b[0m");
+
+        Ok(Response::Accept)
+    })
+}
+
 fn query_type_expression(prj: &mut Project) -> Result<(), Box<dyn Error>> {
     read_and(C_RESV, "ty>", |line| {
         if line.trim().is_empty() {

cl-repl/src/lib.rs

@@ -112,10 +112,16 @@ pub mod program {
             self.parse_file().or_else(|_| self.parse_stmt())
         }
         pub fn parse_stmt(&self) -> PResult<Program<'t, Parsed>> {
-            Ok(Program { data: Parsed::Stmt(Parser::new(self.lex()).stmt()?), text: self.text })
+            let stmt = Parser::new(self.lex()).stmt()?;
+            // let stmt = WhileElseDesugar.fold_stmt(stmt);
+
+            Ok(Program { data: Parsed::Stmt(stmt), text: self.text })
         }
         pub fn parse_file(&self) -> PResult<Program<'t, Parsed>> {
-            Ok(Program { data: Parsed::File(Parser::new(self.lex()).file()?), text: self.text })
+            let file = Parser::new(self.lex()).file()?;
+            // let file = WhileElseDesugar.fold_file(file);
+
+            Ok(Program { data: Parsed::File(file), text: self.text })
         }
     }