Merge pull request #124 from denizzzka/fix_122_attempt_two

Another fix for #122

src/dpq2/conv/from_d_types.d

@@ -139,9 +139,10 @@ if (is(Unqual!T == TimeStamp) || is(Unqual!T == TimeStampUTC))
         );
 }
 
-// Wikipedia's magic
 private auto modJulianDayForIntYear(const int year, const ubyte month, const short day) pure
 {
+    // Wikipedia magic:
+
     const a = (14 - month) / 12;
     const y = year + 4800 - a;
     const m = month + a * 12 - 3;
@@ -358,6 +359,22 @@ unittest
     assert(v.as!DateTime == d);
 }
 
+unittest
+{
+    // Nullable!DateTime
+    import std.typecons : nullable;
+    auto d = nullable(DateTime(2018, 2, 20, 1, 2, 3));
+    auto v = toValue(d);
+
+    assert(v.oidType == OidType.TimeStamp);
+    assert(v.as!(Nullable!DateTime) == d);
+
+    d.nullify();
+    v = toValue(d);
+    assert(v.oidType == OidType.TimeStamp);
+    assert(v.as!(Nullable!DateTime).isNull);
+}
+
 unittest
 {
     // TimeOfDay: '14:29:17'

src/dpq2/oids.d

@@ -167,7 +167,7 @@ OidType detectOidTypeFromNative(T)()
 
 private OidType detectOidTypeNotCareAboutNullable(T)()
 {
-    import std.datetime.date : StdDate = Date, TimeOfDay;
+    import std.datetime.date : StdDate = Date, TimeOfDay, DateTime;
     import std.datetime.systime : SysTime;
     import std.traits : Unqual;
     import std.uuid : StdUUID = UUID;
@@ -188,6 +188,7 @@ private OidType detectOidTypeNotCareAboutNullable(T)()
         static if(is(UT == double)){ return Float8; } else
         static if(is(UT == StdDate)){ return Date; } else
         static if(is(UT == TimeOfDay)){ return Time; } else
+        static if(is(UT == DateTime)){ return TimeStamp; } else
         static if(is(UT == SysTime)){ return TimeStampWithZone; } else
         static if(is(UT == dpq2.conv.time.TimeStamp)){ return TimeStamp; } else
         static if(is(UT == dpq2.conv.time.TimeStampUTC)){ return TimeStampWithZone; } else