pkg/ast: support expressions with ast.Type

So far they have the following grammar:

OP = "==", "!=", "&"

value-expr = value-expr OP value-expr
           | factor

factor = "(" and-expr ")"
         | integer
	 | identifier
         | string

Operators are left associative, e.g. A & B & C is the same as
(A & B) & C.

Further restrictions will be imposed in pkg/compiler.

This will help implement conditionally included fields.

1 files changed, 14 insertions, 1 deletions

diff --git a/pkg/ast/clone.go b/pkg/ast/clone.go
index 0c9c831f0..e23a9eb70 100644
--- a/pkg/ast/clone.go
+++ b/pkg/ast/clone.go
@@ -157,7 +157,7 @@ func (n *Int) Clone() Node {
 }
 
 func (n *Type) Clone() Node {
-	return &Type{
+	ret := &Type{
 		Pos:       n.Pos,
 		Value:     n.Value,
 		ValueFmt:  n.ValueFmt,
@@ -168,6 +168,10 @@ func (n *Type) Clone() Node {
 		Colon:     cloneTypes(n.Colon),
 		Args:      cloneTypes(n.Args),
 	}
+	if n.Expression != nil {
+		ret.Expression = n.Expression.Clone().(*BinaryExpression)
+	}
+	return ret
 }
 
 func (n *Field) Clone() Node {
@@ -181,6 +185,15 @@ func (n *Field) Clone() Node {
 	}
 }
 
+func (n *BinaryExpression) Clone() Node {
+	return &BinaryExpression{
+		Pos:      n.Pos,
+		Operator: n.Operator,
+		Left:     n.Left.Clone().(*Type),
+		Right:    n.Right.Clone().(*Type),
+	}
+}
+
 func cloneFields(list []*Field) (res []*Field) {
 	for _, n := range list {
 		res = append(res, n.Clone().(*Field))