dotnet/BenchmarkDotNet · error · ArgumentException

The constructorBuilder should have non-null DeclaringType.

Error message

The constructorBuilder should have non-null DeclaringType.

What it means

EmitCallBaseParameterlessCtor (internal) requires the ConstructorBuilder to have a non-null DeclaringType so it can resolve the base type's parameterless constructor. It throws ArgumentException otherwise-an internal precondition guarding constructor resolution.

Source

Thrown at src/BenchmarkDotNet/Helpers/Reflection.Emit/IlGeneratorStatementExtensions.cs:13

using System.Reflection;
using System.Reflection.Emit;

namespace BenchmarkDotNet.Helpers.Reflection.Emit
{
    internal static class IlGeneratorStatementExtensions
    {
        public static void EmitCallBaseParameterlessCtor(this ILGenerator ilGenerator, ConstructorBuilder constructorBuilder)
        {
            if (constructorBuilder.IsStatic)
                throw new ArgumentException($"Can not emit base call for {constructorBuilder}");
            if (constructorBuilder.DeclaringType == null)
                throw new ArgumentException($"The {nameof(constructorBuilder)} should have non-null {nameof(constructorBuilder.DeclaringType)}.");

            /*
                IL_0000: ldarg.0
                IL_0001: call instance void [BenchmarkDotNet]BenchmarkDotNet.Samples.SampleBenchmark::.ctor()
            */
            var baseCtor = constructorBuilder.DeclaringType.BaseType?.GetConstructor([]);
            if (baseCtor == null)
                throw new ArgumentException(
                    $"Base type of {constructorBuilder.DeclaringType} has no public parameterless constructor.");

            ilGenerator.Emit(OpCodes.Ldarg_0);
            ilGenerator.Emit(OpCodes.Call, baseCtor);
        }

        public static void EmitCtorReturn(this ILGenerator ilBuilder, ConstructorBuilder methodBuilder)
        {
            // IL_0000: ret
            ilBuilder.Emit(OpCodes.Ret);

View on GitHub (pinned to b515068b61)

Solutions

1. Simplify the benchmark type structure and retry.
2. Upgrade BenchmarkDotNet; file an issue with a minimal repro if it persists.

try { runner.Run(); }
catch (ArgumentException ex) when (ex.Message.Contains("non-null DeclaringType")) { /* simplify type layout, report issue */ }

When it happens

Trigger: The emitter receives a ConstructorBuilder whose DeclaringType is null, so it cannot walk to BaseType to find a parameterless ctor.

Common situations: Library codegen bug while building a generated benchmark type; not user-reachable via normal configuration.

Related errors

• Method {methodToCall} should be static method.
• The methodToCall should have non-null DeclaringType.
• Method {methodToCall} should be instance method.
• The optionalLocalThis should be null for static calls
• Can not emit base call for {constructorBuilder}

AI-assisted analysis of dotnet/BenchmarkDotNet@b515068b61 (2026-08-13). Data as JSON: /api/errors/9acc10107fd3bd62. Report an issue: GitHub.