feat(ast_codegen): introduce the #[span] hint. (#4012)

closes #3904

crates/oxc_ast/src/ast/js.rs

@@ -1344,6 +1344,7 @@ pub struct BindingPattern<'a> {
         feature = "serialize",
         tsify(type = "(BindingIdentifier | ObjectPattern | ArrayPattern | AssignmentPattern)")
     )]
+    #[span]
     pub kind: BindingPatternKind<'a>,
     pub type_annotation: Option<Box<'a, TSTypeAnnotation<'a>>>,
     pub optional: bool,

crates/oxc_ast/src/generated/span.rs

@@ -925,6 +925,13 @@ impl GetSpan for DebuggerStatement {
     }
 }
 
+impl<'a> GetSpan for BindingPattern<'a> {
+    #[inline]
+    fn span(&self) -> Span {
+        self.kind.span()
+    }
+}
+
 impl<'a> GetSpan for BindingPatternKind<'a> {
     fn span(&self) -> Span {
         match self {
@@ -2185,9 +2192,3 @@ impl<'a> GetSpan for JSXText<'a> {
         self.span
     }
 }
-
-impl<'a> GetSpan for BindingPattern<'a> {
-    fn span(&self) -> Span {
-        self.kind.span()
-    }
-}

crates/oxc_ast_macros/src/lib.rs

@@ -22,7 +22,7 @@ pub fn visited_node(_args: TokenStream, input: TokenStream) -> TokenStream {
 /// Dummy derive macro for a non-existent trait `VisitedNode`.
 ///
 /// Does not generate any code, only purpose is to allow using `#[scope]` attr in the type def.
-#[proc_macro_derive(VisitedNode, attributes(scope, visit, visit_as, visit_args))]
+#[proc_macro_derive(VisitedNode, attributes(span, scope, visit, visit_as, visit_args))]
 pub fn visited_node_derive(_item: TokenStream) -> TokenStream {
     TokenStream::new()
 }

tasks/ast_codegen/src/generators/impl_get_span.rs

@@ -15,23 +15,6 @@ use super::generated_header;
 
 pub struct ImplGetSpanGenerator;
 
-const EDGE_CASES: [&str; 1] = ["BindingPattern"];
-
-fn edge_case(it: &std::cell::Ref<RType>) -> bool {
-    !it.ident().is_some_and(|it| EDGE_CASES.contains(&it.to_string().as_str()))
-}
-
-fn edge_case_impls() -> TokenStream {
-    quote! {
-        endl!();
-        impl<'a> GetSpan for BindingPattern<'a> {
-            fn span(&self) -> Span {
-                self.kind.span()
-            }
-        }
-    }
-}
-
 impl Generator for ImplGetSpanGenerator {
     fn name(&self) -> &'static str {
         "ImplGetSpanGenerator"
@@ -44,7 +27,6 @@ impl Generator for ImplGetSpanGenerator {
             .map(|it| it.borrow())
             .filter(|it| it.visitable())
             .filter(|it| matches!(&**it, RType::Enum(_) | RType::Struct(_)))
-            .filter(edge_case)
             .map(|kind| match &*kind {
                 RType::Enum(it) => impl_enum(it),
                 RType::Struct(it) => impl_struct(it),
@@ -52,8 +34,6 @@ impl Generator for ImplGetSpanGenerator {
             })
             .collect();
 
-        let edge_impls = edge_case_impls();
-
         let header = generated_header!();
 
         GeneratorOutput::One(quote! {
@@ -65,9 +45,6 @@ impl Generator for ImplGetSpanGenerator {
             use oxc_span::{GetSpan, Span};
 
             #(#impls)*
-
-            #edge_impls
-
         })
     }
 }
@@ -96,12 +73,20 @@ fn impl_enum(it @ REnum { item, .. }: &REnum) -> TokenStream {
 fn impl_struct(it @ RStruct { item, .. }: &RStruct) -> TokenStream {
     let typ = it.as_type();
     let generics = &item.generics;
+    let inner_span_hint =
+        item.fields.iter().find(|it| it.attrs.iter().any(|a| a.path().is_ident("span")));
+    let span = if let Some(span_field) = inner_span_hint {
+        let ident = span_field.ident.as_ref().unwrap();
+        quote!(#ident.span())
+    } else {
+        quote!(span)
+    };
     quote! {
         endl!();
         impl #generics GetSpan for #typ {
             #[inline]
             fn span(&self) -> Span {
-                self.span
+                self.#span
             }
         }
     }