zclsyntax: "Keyword" type

This is a helper for recognizing identifiers that are actually keywords.

zcl/zclsyntax/keywords.go

@@ -0,0 +1,18 @@
+package zclsyntax
+
+import (
+	"bytes"
+)
+
+type Keyword []byte
+
+var forKeyword = Keyword([]byte{'f', 'o', 'r'})
+var inKeyword = Keyword([]byte{'i', 'n'})
+var ifKeyword = Keyword([]byte{'i', 'f'})
+
+func (kw Keyword) TokenMatches(token Token) bool {
+	if token.Type != TokenIdent {
+		return false
+	}
+	return bytes.Equal([]byte(kw), token.Bytes)
+}