Backport #2015

cli/src/commands/codegen.rs

@@ -210,8 +210,18 @@ fn codegen(
         codegen.no_docs()
     }
 
-    let metadata = subxt_metadata::Metadata::decode(&mut &*metadata_bytes)
-        .map_err(|e| eyre!("Cannot decode the provided metadata: {e}"))?;
+    let metadata = {
+        let mut metadata = subxt_metadata::Metadata::decode(&mut &*metadata_bytes)
+            .map_err(|e| eyre!("Cannot decode the provided metadata: {e}"))?;
+
+        // Run this first to ensure type paths are unique (which may result in 1,2,3 suffixes being added
+        // to type paths), so that when we validate derives/substitutions below, they are allowed for such
+        // types. See <https://github.com/paritytech/subxt/issues/2011>.
+        scale_typegen::utils::ensure_unique_type_paths(metadata.types_mut())
+            .expect("ensure_unique_type_paths should not fail; please report an issue.");
+
+        metadata
+    };
 
     // Configure derives:
     let global_derives = raw_derives