intern struct type the first time it is defined

at that point the fields might not yet have proper types

src/ast2/mod.rs

@@ -977,6 +977,17 @@ impl Ast {
         loc: SourceLocation,
     ) -> Index {
         let i = self.reserve_node();
+        self.set_struct_decl(i, name, flags, fields, loc)
+    }
+
+    fn set_struct_decl<I: IntoIterator<Item = (intern::Index, Index)>>(
+        &mut self,
+        i: Index,
+        name: intern::Index,
+        flags: StructFlags,
+        fields: I,
+        loc: SourceLocation,
+    ) -> Index {
         let (offset, _) = self.extend_extra([flags.pack()]);
         let (names, types) = fields
             .into_iter()
@@ -3885,12 +3896,22 @@ pub mod ast_gen {
                 loc: tokens.current_source_location(),
             })?;
 
+            let decl = self.ast.reserve_node();
             let decl = self.parse_braced(tokens, |this, tokens| {
                 this.parse_struct_fields(tokens).map(|fields| {
                     _ = tokens.eat_token(Token::Comma);
                     let flags =
                         StructFlags::new(packed, c_like, fields.len() as u32);
-                    this.ast.push_struct_decl(name, flags, fields, loc)
+
+                    this.intern.insert_or_replace_struct_type(
+                        name,
+                        decl,
+                        flags.packed,
+                        flags.c_like,
+                        vec![],
+                    );
+
+                    this.ast.set_struct_decl(decl, name, flags, fields, loc)
                 })
             })?;