refactor(transformer/typescript): do not need to go through TSModuleDeclaration if is a NamespaceModule (#10366)

Benefits from #10350. `NamespaceModule` means this `TSModuleDeclaration` is a type-only declaration, so that we can get rid of it early without going through its block.

Author: Dunqing

crates/oxc_syntax/src/symbol.rs

@@ -255,6 +255,11 @@ impl SymbolFlags {
         self.contains(Self::Ambient)
     }
 
+    #[inline]
+    pub fn is_namespace(&self) -> bool {
+        self.contains(Self::NameSpaceModule)
+    }
+
     /// If true, then the symbol can be referenced by a type reference
     #[inline]
     pub fn can_be_referenced_by_type(&self) -> bool {

crates/oxc_transformer/src/typescript/namespace.rs

@@ -111,6 +111,11 @@ impl<'a> TypeScriptNamespace<'a, '_> {
             return;
         };
 
+        // Empty namespace or only have type declarations.
+        if ctx.scoping().symbol_flags(ident.symbol_id()).is_namespace() {
+            return;
+        }
+
         let Some(body) = body else {
             return;
         };
@@ -235,14 +240,6 @@ impl<'a> TypeScriptNamespace<'a, '_> {
             new_stmts.push(stmt);
         }
 
-        if new_stmts.is_empty() {
-            // Delete the scope binding that `ctx.generate_uid` created above,
-            // as no binding is actually being created
-            ctx.scoping_mut().remove_binding(scope_id, uid_binding.name.as_str());
-
-            return;
-        }
-
         if !Self::is_redeclaration_namespace(&ident, ctx) {
             let declaration = Self::create_variable_declaration(&binding, ctx);
             if is_export {