1 files changed, 37 insertions, 0 deletions
diff --git a/compiler/ast.go b/compiler/ast.go
index 0b72f8d..e9c1b50 100644
--- a/compiler/ast.go
+++ b/compiler/ast.go
@@ -2,6 +2,7 @@ package compiler
 
 import (
 	"fmt"
+	"io"
 	"sort"
 	"strings"
 )
@@ -421,3 +422,39 @@ func positionSymbols(node astNode, n uint8) uint8 {
 	}
 	return p
 }
+
+func printAST(w io.Writer, ast astNode, ruledLine string, childRuledLinePrefix string, withAttrs bool) {
+	if ast == nil {
+		return
+	}
+	fmt.Fprintf(w, ruledLine)
+	fmt.Fprintf(w, "node: %v", ast)
+	if withAttrs {
+		fmt.Fprintf(w, ", nullable: %v, first: %v, last: %v", ast.nullable(), ast.first(), ast.last())
+	}
+	fmt.Fprintf(w, "\n")
+	left, right := ast.children()
+	children := []astNode{}
+	if left != nil {
+		children = append(children, left)
+	}
+	if right != nil {
+		children = append(children, right)
+	}
+	num := len(children)
+	for i, child := range children {
+		line := "└─ "
+		if num > 1 {
+			if i == 0 {
+				line = "├─ "
+			} else if i < num-1 {
+				line = "│  "
+			}
+		}
+		prefix := "│  "
+		if i >= num-1 {
+			prefix = "    "
+		}
+		printAST(w, child, childRuledLinePrefix+line, childRuledLinePrefix+prefix, withAttrs)
+	}
+}