Add String() method to parser.Tree

parser/tree.go

@@ -1,6 +1,8 @@
 package parser
 
 import "io"
+import "os"
+import "fmt"
 import "github.com/alecthomas/participle/v2"
 
 var parser = participle.MustBuild[Tree] (
@@ -42,6 +44,14 @@ var parser = participle.MustBuild[Tree] (
 type Tree struct {
 	Declarations []TopLevel `parser:" @@* "`
 }
+func (this *Tree) String () string {
+	out := ""
+	for index, declaration := range this.Declarations {
+		if index > 0 { out += "\n" }
+		out += fmt.Sprint(declaration)
+	}
+	return out
+}
 
 // Parse parses the contents of the given io.Reader into the tree.
 func (this *Tree) Parse (name string, file io.Reader) error {