Add error for non-scalar parameters bound without any values (#71)

CliFx.Tests/ArgumentBindingSpecs.cs

@@ -894,6 +894,31 @@ namespace CliFx.Tests
             });
         }
 
+        [Fact]
+        public void Scalar_properties_annotated_as_parameter_requires_input()
+        {
+            // Arrange
+            var input = new CommandInputBuilder()
+                .Build();
+            
+            // Act & assert
+            var ex = Assert.Throws<CliFxException>(() => CommandHelper.ResolveCommand<ParametersCommand>(input));
+            _output.WriteLine(ex.Message);
+        }
+
+        [Fact]
+        public void NonScalar_properties_annotated_as_parameter_requires_input() 
+        {
+            // Arrange
+            var input = new CommandInputBuilder()
+                .AddParameter("foo")
+                .AddParameter("bar")
+                .Build();
+
+            var ex = Assert.Throws<CliFxException>(() => CommandHelper.ResolveCommand<ParametersCommand>(input));
+            _output.WriteLine(ex.Message);
+        }
+
         [Fact]
         public void Property_annotated_as_parameter_must_always_be_bound_to_some_value()
         {

CliFx/Domain/CommandSchema.cs

@@ -103,7 +103,10 @@ namespace CliFx.Domain
 
             if (nonScalarParameter != null)
             {
-                // TODO: Should it verify that at least one value is passed?
+                // Verify that we have at least one value
+                if(!parameterInputs.Skip(scalarParameters.Length).Any())
+                    throw CliFxException.ParameterNotSet(nonScalarParameter);
+
                 var nonScalarValues = parameterInputs
                     .Skip(scalarParameters.Length)
                     .Select(p => p.Value)