Lexer accepts date with 1- to 3-digit year

[moorereason]

Describe the Bug

The existing dateRegexp accepts years with 1-3 digits. AFAIK, the TOML spec only allows 4-digit years.

To Reproduce

These should be pass, but they do:

diff --git a/lexer_test.go b/lexer_test.go
index 225a52a..e5ac952 100644
--- a/lexer_test.go
+++ b/lexer_test.go
@@ -350,6 +350,24 @@ func TestKeyEqualDate(t *testing.T) {
                {Position{1, 7}, tokenDate, "1979-05-27 07:32:00Z"},
                {Position{1, 27}, tokenEOF, ""},
        })
+       testFlow(t, "foo = 9-05-27 07:32:00Z", []token{
+               {Position{1, 1}, tokenKey, "foo"},
+               {Position{1, 5}, tokenEqual, "="},
+               {Position{1, 7}, tokenDate, "9-05-27 07:32:00Z"},
+               {Position{1, 24}, tokenEOF, ""},
+       })
+       testFlow(t, "foo = 79-05-27 07:32:00Z", []token{
+               {Position{1, 1}, tokenKey, "foo"},
+               {Position{1, 5}, tokenEqual, "="},
+               {Position{1, 7}, tokenDate, "79-05-27 07:32:00Z"},
+               {Position{1, 25}, tokenEOF, ""},
+       })
+       testFlow(t, "foo = 979-05-27 07:32:00Z", []token{
+               {Position{1, 1}, tokenKey, "foo"},
+               {Position{1, 5}, tokenEqual, "="},
+               {Position{1, 7}, tokenDate, "979-05-27 07:32:00Z"},
+               {Position{1, 26}, tokenEOF, ""},
+       })
 }

 func TestFloatEndingWithDot(t *testing.T) {

Expected Behavior

Only allow 4-digit years.

Versions

• go-toml: 5c94d86
• go version go1.15.2 linux/amd64

[pelletier]

Good catch! Thank you!