Rust: distinguish [a, b] from [a; b]

This splits the `ArrayExpr` class into `ArrayListExpr` and `ArrayRepeatExpr`.
This uses the `synth.from_class` machinery to integrate seamlessly into the
generated code, by hiding the extracted `ArrayExpr` behind an internal class
and replacing it with a hierarchy of those two classes under a new
`ArrayExpr` class.

rust/ast-generator/src/main.rs

@@ -21,6 +21,7 @@ fn class_name(type_name: &str) -> String {
         "Fn" => "Function",
         "Literal" => "LiteralExpr",
         "Type" => "TypeRef",
+        "ArrayExpr" => "ArrayExprInternal",
         _ => type_name,
     };
     name.to_owned()
@@ -354,6 +355,13 @@ fn get_fields(node: &AstNodeSrc) -> Vec<FieldInfo> {
                 is_many: false,
             });
         }
+        "ArrayExpr" => {
+            result.push(FieldInfo {
+                name: "is_semicolon".to_string(),
+                tp: "predicate".to_string(),
+                is_many: true,
+            });
+        }
         _ => {}
     }