conlang: Add Quote expression as a hack for testing

Possibly removed later, or replaced with something that turns Conlang AST nodes into Conlang data structures.

compiler/cl-ast/src/ast_impl.rs

@@ -415,6 +415,7 @@ mod display {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
             match self {
                 ExprKind::Empty => "()".fmt(f),
+                ExprKind::Quote(v) => v.fmt(f),
                 ExprKind::Let(v) => v.fmt(f),
                 ExprKind::Assign(v) => v.fmt(f),
                 ExprKind::Modify(v) => v.fmt(f),
@@ -442,6 +443,13 @@ mod display {
         }
     }
 
+    impl Display for Quote {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            let Self { quote } = self;
+            write!(f, "`{quote}`")
+        }
+    }
+
     impl Display for Let {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
             let Self { mutable, name, ty, init } = self;
@@ -764,6 +772,7 @@ mod convert {
         }
         impl From for ExprKind {
             Let => ExprKind::Let,
+            Quote => ExprKind::Quote,
             Assign => ExprKind::Assign,
             Modify => ExprKind::Modify,
             Binary => ExprKind::Binary,