Merge pull request #802 from hashicorp/f-ast-transforms

config/lang: AST transforms into the visitor pattern
This commit is contained in:
Mitchell Hashimoto 2015-01-14 16:40:43 -08:00
commit cef5f22fed
9 changed files with 39 additions and 24 deletions

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@ -6,8 +6,9 @@ import (
// Node is the interface that all AST nodes must implement.
type Node interface {
// Accept is called to dispatch to the visitors.
Accept(Visitor)
// Accept is called to dispatch to the visitors. It must return the
// resulting Node (which might be different in an AST transform).
Accept(Visitor) Node
// Pos returns the position of this node in some source.
Pos() Pos
@ -24,11 +25,18 @@ func (p Pos) String() string {
// Visitors are just implementations of this function.
//
// The function must return the Node to replace this node with. "nil" is
// _not_ a valid return value. If there is no replacement, the original node
// should be returned. We build this replacement directly into the visitor
// pattern since AST transformations are a common and useful tool and
// building it into the AST itself makes it required for future Node
// implementations and very easy to do.
//
// Note that this isn't a true implementation of the visitor pattern, which
// generally requires proper type dispatch on the function. However,
// implementing this basic visitor pattern style is still very useful even
// if you have to type switch.
type Visitor func(Node)
type Visitor func(Node) Node
//go:generate stringer -type=Type

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@ -12,12 +12,12 @@ type Call struct {
Posx Pos
}
func (n *Call) Accept(v Visitor) {
for _, a := range n.Args {
a.Accept(v)
func (n *Call) Accept(v Visitor) Node {
for i, a := range n.Args {
n.Args[i] = a.Accept(v)
}
v(n)
return v(n)
}
func (n *Call) Pos() Pos {

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@ -12,12 +12,12 @@ type Concat struct {
Posx Pos
}
func (n *Concat) Accept(v Visitor) {
for _, n := range n.Exprs {
n.Accept(v)
func (n *Concat) Accept(v Visitor) Node {
for i, expr := range n.Exprs {
n.Exprs[i] = expr.Accept(v)
}
v(n)
return v(n)
}
func (n *Concat) Pos() Pos {

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@ -12,8 +12,8 @@ type LiteralNode struct {
Posx Pos
}
func (n *LiteralNode) Accept(v Visitor) {
v(n)
func (n *LiteralNode) Accept(v Visitor) Node {
return v(n)
}
func (n *LiteralNode) Pos() Pos {

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@ -10,8 +10,8 @@ type VariableAccess struct {
Posx Pos
}
func (n *VariableAccess) Accept(v Visitor) {
v(n)
func (n *VariableAccess) Accept(v Visitor) Node {
return v(n)
}
func (n *VariableAccess) Pos() Pos {

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@ -25,9 +25,9 @@ func (c *IdentifierCheck) Visit(root ast.Node) error {
return c.err
}
func (c *IdentifierCheck) visit(raw ast.Node) {
func (c *IdentifierCheck) visit(raw ast.Node) ast.Node {
if c.err != nil {
return
return raw
}
switch n := raw.(type) {
@ -42,6 +42,9 @@ func (c *IdentifierCheck) visit(raw ast.Node) {
default:
c.createErr(n, fmt.Sprintf("unknown node: %#v", raw))
}
// We never do replacement with this visitor
return raw
}
func (c *IdentifierCheck) visitCall(n *ast.Call) {

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@ -37,9 +37,9 @@ func (v *TypeCheck) Visit(root ast.Node) error {
return v.err
}
func (v *TypeCheck) visit(raw ast.Node) {
func (v *TypeCheck) visit(raw ast.Node) ast.Node {
if v.err != nil {
return
return raw
}
switch n := raw.(type) {
@ -54,6 +54,8 @@ func (v *TypeCheck) visit(raw ast.Node) {
default:
v.createErr(n, fmt.Sprintf("unknown node: %#v", raw))
}
return raw
}
func (v *TypeCheck) visitCall(n *ast.Call) {

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@ -105,9 +105,9 @@ func (v *executeVisitor) Visit(root ast.Node) (interface{}, ast.Type, error) {
return result.Value, result.Type, resultErr
}
func (v *executeVisitor) visit(raw ast.Node) {
func (v *executeVisitor) visit(raw ast.Node) ast.Node {
if v.err != nil {
return
return raw
}
switch n := raw.(type) {
@ -122,6 +122,8 @@ func (v *executeVisitor) visit(raw ast.Node) {
default:
v.err = fmt.Errorf("unknown node: %#v", raw)
}
return raw
}
func (v *executeVisitor) visitCall(n *ast.Call) {

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@ -64,11 +64,11 @@ func TestLookupType(t *testing.T) {
type customUntyped struct{}
func (n customUntyped) Accept(ast.Visitor) {}
func (n customUntyped) Pos() (v ast.Pos) { return }
func (n customUntyped) Accept(ast.Visitor) ast.Node { return n }
func (n customUntyped) Pos() (v ast.Pos) { return }
type customTyped struct{}
func (n customTyped) Accept(ast.Visitor) {}
func (n customTyped) Accept(ast.Visitor) ast.Node { return n }
func (n customTyped) Pos() (v ast.Pos) { return }
func (n customTyped) Type(*Scope) (ast.Type, error) { return ast.TypeString, nil }