time: reject invalid day of month in Parse

There was back-and-forth on this but it has been decided to fix the original
complaint, which was easy.

Fixes #7268.

Change-Id: I6b607c49ad44579086aba2c4f4c5424b97fbed64
Reviewed-on: https://go-review.googlesource.com/17710Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

src/time/format.go

@@ -993,6 +993,11 @@ func parse(layout, value string, defaultLocation, local *Location) (Time, error)
 		hour = 0
 	}
 
+	// Validate the day of the month.
+	if day > daysIn(Month(month), year) {
+		return Time{}, &ParseError{alayout, avalue, "", value, ": day of month out of range"}
+	}
+
 	if z != nil {
 		return Date(year, Month(month), day, hour, min, sec, nsec, z), nil
 	}

src/time/format_test.go

@@ -164,9 +164,6 @@ var parseTests = []ParseTest{
 	// GMT with offset.
 	{"GMT-8", UnixDate, "Fri Feb  5 05:00:57 GMT-8 2010", true, true, 1, 0},
 
-	// Day of month can be out of range.
-	{"Jan 36", UnixDate, "Fri Jan 36 05:00:57 GMT-8 2010", true, true, 1, 0},
-
 	// Accept any number of fractional second digits (including none) for .999...
 	// In Go 1, .999... was completely ignored in the format, meaning the first two
 	// cases would succeed, but the next four would not. Go 1.1 accepts all six.
@@ -196,6 +193,57 @@ func TestParse(t *testing.T) {
 	}
 }
 
+// All parsed with ANSIC.
+var dayOutOfRangeTests = []struct {
+	date string
+	ok   bool
+}{
+	{"Thu Jan 99 21:00:57 2010", false},
+	{"Thu Jan 31 21:00:57 2010", true},
+	{"Thu Jan 32 21:00:57 2010", false},
+	{"Thu Feb 28 21:00:57 2012", true},
+	{"Thu Feb 29 21:00:57 2012", true},
+	{"Thu Feb 29 21:00:57 2010", false},
+	{"Thu Mar 31 21:00:57 2010", true},
+	{"Thu Mar 32 21:00:57 2010", false},
+	{"Thu Apr 30 21:00:57 2010", true},
+	{"Thu Apr 31 21:00:57 2010", false},
+	{"Thu May 31 21:00:57 2010", true},
+	{"Thu May 32 21:00:57 2010", false},
+	{"Thu Jun 30 21:00:57 2010", true},
+	{"Thu Jun 31 21:00:57 2010", false},
+	{"Thu Jul 31 21:00:57 2010", true},
+	{"Thu Jul 32 21:00:57 2010", false},
+	{"Thu Aug 31 21:00:57 2010", true},
+	{"Thu Aug 32 21:00:57 2010", false},
+	{"Thu Sep 30 21:00:57 2010", true},
+	{"Thu Sep 31 21:00:57 2010", false},
+	{"Thu Oct 31 21:00:57 2010", true},
+	{"Thu Oct 32 21:00:57 2010", false},
+	{"Thu Nov 30 21:00:57 2010", true},
+	{"Thu Nov 31 21:00:57 2010", false},
+	{"Thu Dec 31 21:00:57 2010", true},
+	{"Thu Dec 32 21:00:57 2010", false},
+}
+
+func TestParseDayOutOfRange(t *testing.T) {
+	for _, test := range dayOutOfRangeTests {
+		_, err := Parse(ANSIC, test.date)
+		switch {
+		case test.ok && err == nil:
+			// OK
+		case !test.ok && err != nil:
+			if !strings.Contains(err.Error(), "day of month out of range") {
+				t.Errorf("%q: expected 'day of month' error, got %v", test.date, err)
+			}
+		case test.ok && err != nil:
+			t.Errorf("%q: unexpected error: %v", test.date, err)
+		case !test.ok && err == nil:
+			t.Errorf("%q: expected 'day of month' error, got none", test.date)
+		}
+	}
+}
+
 func TestParseInLocation(t *testing.T) {
 	// Check that Parse (and ParseInLocation) understand that
 	// Feb 01 AST (Arabia Standard Time) and Feb 01 AST (Atlantic Standard Time)