Add Ast as top level enum

ast/asdl_rs.py

@@ -289,7 +289,40 @@ class StructVisitor(EmitVisitor):
     def __init__(self, *args, **kw):
         super().__init__(*args, **kw)
 
+    def emit_attrs(self, depth):
+        self.emit("#[derive(Clone, Debug, PartialEq)]", depth)
+
+    def emit_range(self, has_attributes, depth):
+        if has_attributes:
+            self.emit("pub range: R,", depth + 1)
+        else:
+            self.emit("pub range: OptionalRange<R>,", depth + 1)
+
     def visitModule(self, mod):
+        self.emit_attrs(0)
+        self.emit("""
+        #[derive(is_macro::Is)]
+        pub enum Ast<R=TextRange> {
+        """, 0)
+        for dfn in mod.dfns:
+            rust_name = rust_type_name(dfn.name)
+            generics = "" if self.type_info[dfn.name].is_simple else "<R>"
+            if dfn.name == "mod":
+                # This is exceptional rule to other enums.
+                # Unlike other enums, this is justified because `Mod` is only used as
+                # the top node of parsing result and never a child node of other nodes.
+                # Because it will be very rarely used in very particular applications,
+                # "ast_" prefix to everywhere seems less useful.
+                self.emit('#[is(name = "module")]', 1)
+            self.emit(f"{rust_name}({rust_name}{generics}),", 1)
+        self.emit("""
+        }
+        impl<R> Node for Ast<R> {
+            const NAME: &'static str = "AST";
+            const FIELD_NAMES: &'static [&'static str] = &[];
+        }
+        """, 0)
+
         for dfn in mod.dfns:
             self.visit(dfn)
 
@@ -313,15 +346,6 @@ class StructVisitor(EmitVisitor):
             depth,
         )
 
-    def emit_attrs(self, depth):
-        self.emit("#[derive(Clone, Debug, PartialEq)]", depth)
-
-    def emit_range(self, has_attributes, depth):
-        if has_attributes:
-            self.emit("pub range: R,", depth + 1)
-        else:
-            self.emit("pub range: OptionalRange<R>,", depth + 1)
-
     def simple_sum(self, sum, type, depth):
         rust_name = rust_type_name(type.name)
         self.emit_attrs(depth)

ast/src/gen/generic.rs

@@ -1,6 +1,34 @@
 // File automatically generated by ast/asdl_rs.py.
 
 use crate::text_size::TextRange;
+#[derive(Clone, Debug, PartialEq)]
+#[derive(is_macro::Is)]
+pub enum Ast<R = TextRange> {
+    #[is(name = "module")]
+    Mod(Mod<R>),
+    Stmt(Stmt<R>),
+    Expr(Expr<R>),
+    ExprContext(ExprContext),
+    Boolop(Boolop),
+    Operator(Operator),
+    Unaryop(Unaryop),
+    Cmpop(Cmpop),
+    Comprehension(Comprehension<R>),
+    Excepthandler(Excepthandler<R>),
+    Arguments(Arguments<R>),
+    Arg(Arg<R>),
+    Keyword(Keyword<R>),
+    Alias(Alias<R>),
+    Withitem(Withitem<R>),
+    MatchCase(MatchCase<R>),
+    Pattern(Pattern<R>),
+    TypeIgnore(TypeIgnore<R>),
+}
+impl<R> Node for Ast<R> {
+    const NAME: &'static str = "AST";
+    const FIELD_NAMES: &'static [&'static str] = &[];
+}
+
 #[derive(Clone, Debug, PartialEq)]
 pub struct ModModule<R = TextRange> {
     pub range: OptionalRange<R>,