When generating code from a valid OpenAPI spec, ogen produces a type switch with duplicate case statements, resulting in Go compilation error.

Reproduction

Using spec from: https://github.com/gojitsu/jitsu

ogen --target /tmp/test --clean carriers/jitsu/specs/openapi.yaml
cd /tmp/test && go mod init test && go mod tidy && go build ./...

Error

./oas_response_encoders_gen.go:42:7: duplicate case *NewShipmentResponseStatusCode in type switch
	./oas_response_encoders_gen.go:17:7: previous case

Generated Code (oas_response_encoders_gen.go)

func encodeNewShipmentResponse(response NewShipmentRes, w http.ResponseWriter, span trace.Span) error {
	switch v := response.(type) {
	case *NewShipmentResponseStatusCode:  // Line 17
		// ...
	// ... other cases ...
	case *NewShipmentResponseStatusCode:  // Line 42 - DUPLICATE!
		// ...
	}
}

Expected

Generated Go code should compile without errors

Actual

Duplicate case statements in generated switch statement - Go compilation fails

Impact

Valid OpenAPI 3.0.1 spec cannot generate working Go client. This is a critical bug as the spec is valid but codegen produces invalid Go.

Environment

• ogen version: v1.16.0
• Go version: 1.21+
• OS: macOS

Context

Discovered while validating 20 carrier/logistics API specs. This appears to be related to how ogen generates response encoders when multiple response status codes share the same schema type.