Fix #3189: Support primitive types in Expression.Constant(object) pattern.

ICSharpCode.Decompiler/IL/Transforms/TransformExpressionTrees.cs

@@ -20,7 +20,6 @@ using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
-using System.Reflection;
 
 using ICSharpCode.Decompiler.CSharp.Resolver;
 using ICSharpCode.Decompiler.Semantics;
@@ -1423,7 +1422,15 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 				value = call.Arguments[0];
 				if (call.Arguments.Count == 2)
 					return MatchGetTypeFromHandle(call.Arguments[1], out type);
-				type = value.InferType(context.TypeSystem);
+				type = value switch {
+					LdNull => SpecialType.NullType,
+					LdStr => context.TypeSystem.FindType(KnownTypeCode.String),
+					LdcF4 => context.TypeSystem.FindType(KnownTypeCode.Single),
+					LdcF8 => context.TypeSystem.FindType(KnownTypeCode.Double),
+					LdcI4 => context.TypeSystem.FindType(KnownTypeCode.Int32),
+					LdcI8 => context.TypeSystem.FindType(KnownTypeCode.Int64),
+					_ => value.InferType(context.TypeSystem),
+				};
 				return true;
 			}
 			return false;