Add a method to output enum variant name

Summary:
Will use this to improve our current error message and logging. Right now, we have a generic message on unsupported flow type, but we don't know which flow type is invovled

used in next diff in the stack

Reviewed By: evanyeung

Differential Revision: D58311850

fbshipit-source-id: 9550741d2591e8b00e935ae5ee618dcd41548f37

unsupported/hermes/crates/hermes_estree/src/generated_extensions.rs

@@ -31,6 +31,10 @@ pub trait Range {
     fn range(&self) -> SourceRange;
 }
 
+pub trait Introspection {
+    fn name(&self) -> &'static str;
+}
+
 impl Default for SourceType {
     fn default() -> Self {
         Self::Module

unsupported/hermes/crates/hermes_estree_codegen/src/codegen.rs

@@ -153,7 +153,7 @@ impl Grammar {
             use std::num::NonZeroU32;
             use serde::ser::{Serializer, SerializeMap};
             use serde::{Serialize,Deserialize};
-            use crate::{JsValue, Binding, SourceRange, Number, ESTreeNode, Range};
+            use crate::{JsValue, Binding, SourceRange, Number, ESTreeNode, Range, Introspection};
 
             #(#object_defs)*
 
@@ -765,6 +765,11 @@ impl Enum {
             quote!(Self::#variant(node) => node.range())
         });
 
+        let name_variants = sorted_variants.iter().map(|name| {
+            let variant = format_ident!("{}", name);
+            quote!(Self::#variant(_) => #name)
+        });
+
         quote! {
             #[derive(Serialize, Clone, Debug)]
             #[serde(untagged)]
@@ -797,6 +802,14 @@ impl Enum {
                     }
                 }
             }
+
+            impl Introspection for #name {
+                fn name(&self) -> &'static str {
+                    match self {
+                        #(#name_variants),*
+                    }
+                }
+            }
         }
     }