prog: support AUTO for structs

The AUTO token can currently be used in place of ConstType, LenType, and
CsumType. This commit extends this support to StructType on the
condition that they are made of the above types. It will allow us to
simplify all the {AUTO, AUTO, AUTO, AUTO} in test programs.

The following struct can therefore be written as AUTO.

    auto_struct1 {
        f0 len[parent, int32]
        f1 const[0x43, int32]
    }

In addition, with this commit, AUTO can also stand for nested structs as
long as all the leaf fields are ConstType, LenType, or CsumType. For
example, the following struct can be written as AUTO.

    auto_struct2 {
        f0 len[parent, int32]
        f1 auto_struct1
    }

Suggested-by: Aleksandr Nogikh <nogikh@google.com>
Signed-off-by: Paul Chaignon <paul.chaignon@gmail.com>

1 files changed, 13 insertions, 2 deletions

diff --git a/prog/encoding.go b/prog/encoding.go
index be883645b..6d7daeacb 100644
--- a/prog/encoding.go
+++ b/prog/encoding.go
@@ -489,9 +489,20 @@ func (p *parser) parseArgInt(typ Type, dir Dir) (Arg, error) {
 }
 
 func (p *parser) parseAuto(typ Type, dir Dir) (Arg, error) {
-	switch typ.(type) {
+	switch t1 := typ.(type) {
 	case *ConstType, *LenType, *CsumType:
 		return p.auto(MakeConstArg(typ, dir, 0)), nil
+	case *StructType:
+		var inner []Arg
+		for len(inner) < len(t1.Fields) {
+			field := t1.Fields[len(inner)]
+			innerArg, err := p.parseAuto(field.Type, dir)
+			if err != nil {
+				return nil, err
+			}
+			inner = append(inner, innerArg)
+		}
+		return MakeGroupArg(typ, dir, inner), nil
 	default:
 		return nil, fmt.Errorf("wrong type %T for AUTO", typ)
 	}
@@ -562,7 +573,7 @@ func (p *parser) parseArgAddr(typ Type, dir Dir) (Arg, error) {
 	var inner Arg
 	if p.Char() == '=' {
 		p.Parse('=')
-		if p.Char() == 'A' {
+		if p.HasNext("ANY") {
 			p.Parse('A')
 			p.Parse('N')
 			p.Parse('Y')