fix #1137

Author: jonsequitur

src/System.CommandLine.Tests/Binding/ModelBinderTests.cs

@@ -5,6 +5,7 @@
 using System.CommandLine.Binding;
 using System.CommandLine.Builder;
 using System.CommandLine.Invocation;
+using System.CommandLine.IO;
 using System.CommandLine.Parsing;
 using System.IO;
 using FluentAssertions;
@@ -769,5 +770,29 @@ public async Task Empty_input_is_bound_correctly_to_list_type_properties()
 
             boundInstance.Should().NotBeNull();
         }
+
+        [Fact]
+        public async Task Decimals_are_bound_correctly_when_no_token_is_matched()
+        {
+            decimal? receivedValue = null;
+
+            var rootCommand = new RootCommand
+            {
+                new Option<decimal>("--opt-decimal")
+            };
+            rootCommand.Handler = CommandHandler.Create((ComplexType options) =>
+            {
+                receivedValue = options.OptDecimal;
+            });
+
+            await rootCommand.InvokeAsync("");
+
+            receivedValue.Should().Be(0);
+        }
+
+        public class ComplexType
+        {
+            public decimal OptDecimal { get; set; }
+        }
     }
 }

src/System.CommandLine/Binding/ModelBinder.cs

@@ -105,7 +105,8 @@ private bool ShortCutTheBinding()
             var modelType = ModelDescriptor.ModelType;
             return modelType.IsPrimitive ||
                    modelType.IsNullableValueType() ||
-                   modelType == typeof(string);
+                   modelType == typeof(string) ||
+                   modelType == typeof(decimal) ;
         }
 
         private (bool success, object? newInstance, bool anyNonDefaults) GetSimpleModelValue(