What causes "failed to process type %s: %w" in vitessio/vitess?

Read the wrapped cause (error 449 or a generator failure) and fix the root generator issue

failed to process type %s: %w

Error message

failed to process type %s: %w

What it means

processTypeQueue dequeues each discovered type name and runs it through processTypeWithGenerators. Any failure from a generator is wrapped with this message identifying the type, so the caller knows which type's helper generation failed.

Source

Thrown at go/tools/asthelpergen/asthelpergen.go:368

		return nil, err
	}
	return gen.generateOutputFiles(), nil
}

// processTypeQueue processes all types in the todo queue with all generators
func (gen *astHelperGen) processTypeQueue() error {
	alreadyDone := map[string]bool{}
	for len(gen.todo) > 0 {
		t := gen.todo[0]
		typeName := printableTypeName(t)
		gen.todo = gen.todo[1:]

		if alreadyDone[typeName] {
			continue
		}

		if err := gen.processTypeWithGenerators(t); err != nil {
			return fmt.Errorf("failed to process type %s: %w", typeName, err)
		}
		alreadyDone[typeName] = true
	}
	return nil
}

// processTypeWithGenerators dispatches a type to all generators based on its underlying type
func (gen *astHelperGen) processTypeWithGenerators(t types.Type) error {
	underlying := t.Underlying()
	typeName := printableTypeName(t)

	for _, g := range gen.gens {
		var err error
		switch underlying := underlying.(type) {
		case *types.Interface:
			err = g.interfaceMethod(t, underlying, gen)
		case *types.Slice:
			err = g.sliceMethod(t, underlying, gen)

View on GitHub (pinned to 01a25a7d17)

Solutions

Read the wrapped cause (error 449 or a generator failure) and fix the root generator issue
Add or extend a generator to support the type's underlying kind (interface/pointer/struct/basic/map/slice)
Exclude the unsupported type from generation if it should not receive helpers

Defensive patterns

Strategy: try-catch

Try / catch

if err := gen.createFiles(); err != nil {
    if strings.HasPrefix(err.Error(), "failed to process type ") {
        typeName := extractTypeName(err.Error())
        log.Printf("fix generator for type %s: %v", typeName, err)
    }
    return err
}

Prevention

Read the wrapped cause before changing top-level queue code
Extend generators whenever new AST types with new underlying kinds are added
Run codegen locally after adding any new node type

When it happens

Trigger: processTypeWithGenerators returns an error for a type (e.g. an unsupported underlying type or a sub-generator failure) while draining the type queue created by createFiles.

Common situations: A newly added AST type with an underlying kind no generator supports; cascading failure from an earlier generation bug surfacing at the queue-processing level.

Related errors

AI-assisted analysis of vitessio/vitess@01a25a7d17 (2026-09-01). Data as JSON: /api/errors/f950cf0818074814. Report an issue: GitHub.