scanner: cut keyword lookups in half

vlib/v/scanner/scanner.v

@@ -580,8 +580,8 @@ pub fn (mut s Scanner) scan() token.Token {
 		// tmp hack to detect . in ${}
 		// Check if not .eof to prevent panic
 		next_char := if s.pos + 1 < s.text.len { s.text[s.pos + 1] } else { `\0` }
-		if token.is_key(name) {
-			kind := token.key_to_token(name)
+		kind := token.keywords[name]
+		if kind != .unknown {
 			if kind == .key_fn {
 				s.struct_name = s.ident_struct_name()
 				s.fn_name = s.ident_fn_name()

vlib/v/token/token.v

@@ -14,6 +14,7 @@ pub:
 }
 
 pub enum Kind {
+	unknown
 	eof
 	name // user
 	number // 123
@@ -133,8 +134,8 @@ const (
 )
 // build_keys genereates a map with keywords' string values:
 // Keywords['return'] == .key_return
-fn build_keys() map[string]int {
-	mut res := map[string]int
+fn build_keys() map[string]Kind {
+	mut res := map[string]Kind
 	for t in int(Kind.keyword_beg) + 1 .. int(Kind.keyword_end) {
 		key := token_str[t]
 		res[key] = t
@@ -145,6 +146,7 @@ fn build_keys() map[string]int {
 // TODO remove once we have `enum Kind { name('name') if('if') ... }`
 fn build_token_str() []string {
 	mut s := [''].repeat(nr_tokens)
+	s[Kind.unknown] = 'unknown'
 	s[Kind.eof] = 'eof'
 	s[Kind.name] = 'name'
 	s[Kind.number] = 'number'