Allow nulls in string[] custom attribute data

The existing schema didn't allow it and we were crashing the compiler. Turns out this is popular in xUnit tests in the CoreFX tree.

Includes:
* Schema update that makes string[] more like object[] than arrays of primitive types
* Updates to both of our emitters
* Update to the reflection reader
* Unit test

[tfs-changeset: 1650932]

2 files changed, 5 insertions, 22 deletions

diff --git a/src/ILCompiler.MetadataWriter/src/Internal/Metadata/NativeFormat/Writer/MdBinaryWriterGen.cs b/src/ILCompiler.MetadataWriter/src/Internal/Metadata/NativeFormat/Writer/MdBinaryWriterGen.cs
index e49f28b49..344b478ec 100644
--- a/src/ILCompiler.MetadataWriter/src/Internal/Metadata/NativeFormat/Writer/MdBinaryWriterGen.cs
+++ b/src/ILCompiler.MetadataWriter/src/Internal/Metadata/NativeFormat/Writer/MdBinaryWriterGen.cs
@@ -46,20 +46,6 @@ namespace Internal.Metadata.NativeFormat.Writer
             }
         } // Write
 
-        public static void Write(this NativeWriter writer, string[] values)
-        {
-            if (values == null)
-            {
-                writer.WriteUnsigned(0);
-                return;
-            }
-            writer.WriteUnsigned((uint)values.Length);
-            foreach (string value in values)
-            {
-                writer.Write(value);
-            }
-        } // Write
-
         public static void Write(this NativeWriter writer, byte[] values)
         {
             if (values == null)
diff --git a/src/ILCompiler.MetadataWriter/src/Internal/Metadata/NativeFormat/Writer/NativeFormatWriterGen.cs b/src/ILCompiler.MetadataWriter/src/Internal/Metadata/NativeFormat/Writer/NativeFormatWriterGen.cs
index b18563205..25f9a44cb 100644
--- a/src/ILCompiler.MetadataWriter/src/Internal/Metadata/NativeFormat/Writer/NativeFormatWriterGen.cs
+++ b/src/ILCompiler.MetadataWriter/src/Internal/Metadata/NativeFormat/Writer/NativeFormatWriterGen.cs
@@ -1583,6 +1583,7 @@ namespace Internal.Metadata.NativeFormat.Writer
 
         internal override void Visit(IRecordVisitor visitor)
         {
+            Value = visitor.Visit(this, Value);
         } // Visit
 
         public override sealed bool Equals(Object obj)
@@ -1600,13 +1601,6 @@ namespace Internal.Metadata.NativeFormat.Writer
                 return _hash;
             EnterGetHashCode();
             int hash = -229915937;
-            if (Value != null)
-            {
-                for (int i = 0; i < Value.Length; i++)
-                {
-                    hash = ((hash << 13) - (hash >> 19)) ^ Value[i].GetHashCode();
-                }
-            }
             LeaveGetHashCode();
             _hash = hash;
             return _hash;
@@ -1614,6 +1608,9 @@ namespace Internal.Metadata.NativeFormat.Writer
 
         internal override void Save(NativeWriter writer)
         {
+            Debug.Assert(Value.TrueForAll(handle => handle == null ||
+                handle.HandleType == HandleType.ConstantStringValue ||
+                handle.HandleType == HandleType.ConstantReferenceValue));
             writer.Write(Value);
         } // Save
 
@@ -1637,7 +1634,7 @@ namespace Internal.Metadata.NativeFormat.Writer
             }
         } // Handle
 
-        public String[] Value;
+        public List<MetadataRecord> Value = new List<MetadataRecord>();
     } // ConstantStringArray
 
     public partial class ConstantStringValue : MetadataRecord