Should provide more specific error message when cardinality of a tuple literal doesn't match target tuple type.

Description

        [Fact]
        public void TupleTypeMismatch_01()
        {
            var source = @"
class C
{
    static void Main()
    {
        (int, string) x = (1, ""hello"", 2);
    }
}
" + trivial2uple + trivial3uple;

            CreateCompilationWithMscorlib(source, parseOptions: TestOptions.Regular.WithTuplesFeature()).VerifyDiagnostics(
                // (6,27): error CS0029: Cannot implicitly convert type '(int, string, int)' to '(int, string)'
                //         (int, string) x = (1, "hello", 2);
                Diagnostic(ErrorCode.ERR_NoImplicitConv, @"(1, ""hello"", 2)").WithArguments("(int, string, int)", "(int, string)").WithLocation(6, 27));
        }

Contributor guide

Tech stack

csharp

Domain

developer experience

Issue type

feature

DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.

3

Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.

half day

Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.

stale

ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.

clear

Prerequisites

C# knowledgeRoslyn compiler internals

Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.

30

Research direction

The issue is about improving the error message for tuple type mismatch when cardinality differs. Investigate the Roslyn compiler's error generation for CS0029 (Cannot implicitly convert type) and modify the message to explicitly mention cardinality mismatch. Look at the existing tests in the test suite for tuple type mismatch to understand the expected behavior. The change is likely in the binding or error reporting code within the `src/Compilers/CSharp/Portable` directory.