vitessio/vitess · error

unknown ASTStep

Error message

unknown ASTStep

What it means

In the generated AST-path machinery, DebugString maps each ASTStep enum value to a human-readable path element name. When a step value has no case in the switch, it panics 'unknown ASTStep', meaning a new step constant was added without updating this (manually maintained) integration file. Used for debugging AST paths collected during rewriting.

Source

Thrown at go/tools/asthelpergen/integration/ast_path.go:85

		return "(ValueSliceContainer).ASTImplementationElements"
	case SliceOfASTOffset:
		return "([]AST)[]Offset"
	case SliceOfRefOfLeafOffset:
		return "([]*Leaf)[]Offset"
	case RefOfValueContainerASTType:
		return "(*ValueContainer).ASTType"
	case RefOfValueContainerASTImplementationType:
		return "(*ValueContainer).ASTImplementationType"
	case RefOfValueSliceContainerASTElementsOffset:
		return "(*ValueSliceContainer).ASTElementsOffset"
	case RefOfValueSliceContainerASTImplementationElements:
		return "(*ValueSliceContainer).ASTImplementationElements"
	case RefOfOptionsl:
		return "(*Options).l"
	case VisitableInner:
		return "VisitableInner"
	}
	panic("unknown ASTStep")
}

func GetNodeFromPath(node AST, path ASTPath) AST {
	for len(path) >= 2 {
		step := path.nextPathStep()
		path = path[2:]
		switch step {
		case InterfaceSliceOffset:
			idx, bytesRead := path.nextPathOffset()
			path = path[bytesRead:]
			node = node.(InterfaceSlice)[idx]
		case LeafSliceOffset:
			idx, bytesRead := path.nextPathOffset()
			path = path[bytesRead:]
			node = node.(LeafSlice)[idx]
		case RefOfRefContainerASTType:
			node = node.(*RefContainer).ASTType
		case RefOfRefContainerASTImplementationType:

View on GitHub (pinned to 01a25a7d17)

Solutions

1. Add a case for the missing step constant in the DebugString switch in go/tools/asthelpergen/integration/ast_path.go
2. Regenerate/update the integration files so the step enum and DebugString stay in sync
3. As a workaround, use GetNodeFromPath directly instead of DebugString for the path in question

Example fix

// before
case VisitableInner:
	return "VisitableInner"
}
// after
case VisitableInner:
	return "VisitableInner"
case NewStepKind:
	return "(*SomeNode).NewField"
}

// Ensure every ASTStep constant has a DebugString case
for step := range allASTSteps {
    if nameForStep(step) == "" {
        log.Fatalf("ASTStep %d missing DebugString case", step)
    }
}

When it happens

Trigger: Collecting an ASTPath (a.collectPaths / AddStep) whose step constant is not listed in DebugString's switch, then calling DebugString on it; typically after adding a new node/field step constant in go/tools/asthelpergen without updating ast_path.go.

Common situations: A developer adds a new AST node type or field, the enum grows, and a debug print of a collected path crashes during sqlparser work or tests that enable path collection.

Related errors

• [BUG] tried to replace 'ASTType' on 'ValueContainer'
• unknown ASTStep
• table expression is complex
• package '%s' does not contain 'ast_format.go'
• generator failed for type %s: %w

AI-assisted analysis of vitessio/vitess@01a25a7d17 (2026-09-01). Data as JSON: /api/errors/2f8b96b42adbdb6f. Report an issue: GitHub.