syntax: accept "declare $name" again

This is a regression from v1. Let's keep "declare $foo" where
foo=name=val out of the question for now, as that opens an entire new
world.

Fixes #129.

syntax/filetests_test.go

@@ -3213,14 +3213,14 @@ var fileTests = []testCase{
 		),
 	},
 	{
-		Strs: []string{"declare -f func >/dev/null"},
+		Strs: []string{"declare -f $func >/dev/null"},
 		bash: &Stmt{
 			Cmd: &DeclClause{
 				Variant: lit("declare"),
 				Opts:    litWords("-f"),
 				Assigns: []*Assign{{
 					Naked: true,
-					Name:  lit("func"),
+					Value: word(litParamExp("func")),
 				}},
 			},
 			Redirs: []*Redirect{

syntax/nodes.go

@@ -180,6 +180,10 @@ func (*CoprocClause) commandNode() {}
 // an associative array. In the former, it's just an arithmetic
 // expression. In the latter, it will be a word with a single DblQuoted
 // part.
+//
+// If Naked is true, it's part of a DeclClause and doesn't contain a
+// value. In that context, if the name wasn't a literal, it will be in
+// Value instead of Name.
 type Assign struct {
 	Append bool // +=
 	Naked  bool // without '='
@@ -189,7 +193,13 @@ type Assign struct {
 	Array  *ArrayExpr // =(arr)
 }
 
-func (a *Assign) Pos() Pos { return a.Name.Pos() }
+func (a *Assign) Pos() Pos {
+	if a.Name == nil {
+		return a.Value.Pos()
+	}
+	return a.Name.Pos()
+}
+
 func (a *Assign) End() Pos {
 	if a.Value != nil {
 		return a.Value.End()

syntax/parser.go

@@ -1842,6 +1842,11 @@ func (p *Parser) declClause() *DeclClause {
 				Naked: true,
 				Name:  p.getLit(),
 			})
+		} else if w := p.getWord(); w != nil {
+			ds.Assigns = append(ds.Assigns, &Assign{
+				Naked: true,
+				Value: w,
+			})
 		} else {
 			p.followErr(p.pos, ds.Variant.Value, "names or assignments")
 		}

syntax/parser_test.go

@@ -1309,8 +1309,8 @@ var shellTests = []errorCase{
 		bash: `1:7: "local" must be followed by names or assignments`,
 	},
 	{
-		in:   "declare 0=${o})",
-		bash: `1:9: "declare" must be followed by names or assignments`,
+		in:   "declare 0=${o})", // TODO: better error
+		bash: `1:15: statements must be separated by &, ; or a newline`,
 	},
 	{
 		in:   "a=(<)",