Initial QSfera import

Server/vendor/github.com/open-policy-agent/opa/v1/ir/walk.go

@@ -0,0 +1,93 @@
+// Copyright 2018 The OPA Authors.  All rights reserved.
+// Use of this source code is governed by an Apache2
+// license that can be found in the LICENSE file.
+
+package ir
+
+// Visitor defines the interface for visiting IR nodes.
+type Visitor interface {
+	Before(x any)
+	Visit(x any) (Visitor, error)
+	After(x any)
+}
+
+// Walk invokes the visitor for nodes under x.
+func Walk(vis Visitor, x any) error {
+	impl := walkerImpl{
+		vis: vis,
+	}
+	impl.walk(x)
+	return impl.err
+}
+
+type walkerImpl struct {
+	vis Visitor
+	err error
+}
+
+func (w *walkerImpl) walk(x any) {
+	if w.err != nil { // abort on error
+		return
+	}
+	if x == nil {
+		return
+	}
+
+	prev := w.vis
+	w.vis.Before(x)
+	defer w.vis.After(x)
+	w.vis, w.err = w.vis.Visit(x)
+	if w.err != nil {
+		return
+	} else if w.vis == nil {
+		w.vis = prev
+		return
+	}
+
+	switch x := x.(type) {
+	case *Policy:
+		w.walk(x.Static)
+		w.walk(x.Plans)
+		w.walk(x.Funcs)
+	case *Static:
+		for _, s := range x.Strings {
+			w.walk(s)
+		}
+		for _, f := range x.BuiltinFuncs {
+			w.walk(f)
+		}
+		for _, f := range x.Files {
+			w.walk(f)
+		}
+	case *Plans:
+		for _, pl := range x.Plans {
+			w.walk(pl)
+		}
+	case *Funcs:
+		for _, fn := range x.Funcs {
+			w.walk(fn)
+		}
+	case *Func:
+		for _, b := range x.Blocks {
+			w.walk(b)
+		}
+	case *Plan:
+		for _, b := range x.Blocks {
+			w.walk(b)
+		}
+	case *Block:
+		for _, s := range x.Stmts {
+			w.walk(s)
+		}
+	case *BlockStmt:
+		for _, b := range x.Blocks {
+			w.walk(b)
+		}
+	case *ScanStmt:
+		w.walk(x.Block)
+	case *NotStmt:
+		w.walk(x.Block)
+	case *WithStmt:
+		w.walk(x.Block)
+	}
+}