Fix TimeSpan support in sourcegen (#62130)

* fix TimeSpan support in sourcegen

* address feedback

Author: eiriktsarpalis

src/libraries/System.Text.Json/gen/JsonSourceGenerator.Parser.cs

@@ -80,6 +80,7 @@ private sealed class Parser
             private readonly Type _objectType;
             private readonly Type _stringType;
 
+            private readonly Type? _timeSpanType;
             private readonly Type? _dateTimeOffsetType;
             private readonly Type? _byteArrayType;
             private readonly Type? _guidType;
@@ -202,6 +203,7 @@ public Parser(Compilation compilation, in JsonSourceGenerationContext sourceGene
 
                 _booleanType = _metadataLoadContext.Resolve(SpecialType.System_Boolean);
                 _charType = _metadataLoadContext.Resolve(SpecialType.System_Char);
+                _timeSpanType = _metadataLoadContext.Resolve(typeof(TimeSpan));
                 _dateTimeType = _metadataLoadContext.Resolve(SpecialType.System_DateTime);
                 _nullableOfTType = _metadataLoadContext.Resolve(SpecialType.System_Nullable_T);
                 _objectType = _metadataLoadContext.Resolve(SpecialType.System_Object);
@@ -1506,6 +1508,7 @@ private void PopulateKnownTypes()
                 _knownTypes.Add(_stringType);
 
                 AddTypeIfNotNull(_knownTypes, _byteArrayType);
+                AddTypeIfNotNull(_knownTypes, _timeSpanType);
                 AddTypeIfNotNull(_knownTypes, _dateTimeOffsetType);
                 AddTypeIfNotNull(_knownTypes, _guidType);
                 AddTypeIfNotNull(_knownTypes, _uriType);

src/libraries/System.Text.Json/tests/System.Text.Json.SourceGeneration.Tests/RealWorldContextTests.cs

@@ -399,7 +399,8 @@ protected static ActiveOrUpcomingEvent CreateActiveOrUpcomingEvent()
                 EndDate = DateTime.UtcNow.AddYears(1),
                 Name = "Just a name",
                 ImageUrl = "https://www.dotnetfoundation.org/theme/img/carousel/foundation-diagram-content.png",
-                StartDate = DateTime.UtcNow
+                StartDate = DateTime.UtcNow,
+                Offset = TimeSpan.FromHours(2)
             };
         }
 

src/libraries/System.Text.Json/tests/System.Text.Json.SourceGeneration.Tests/TestClasses.cs

@@ -60,6 +60,7 @@ public class ActiveOrUpcomingEvent
         public string Description { get; set; }
         public DateTimeOffset StartDate { get; set; }
         public DateTimeOffset EndDate { get; set; }
+        public TimeSpan Offset { get; set; }
     }
 
     public class CampaignSummaryViewModel