Bug: Exception compiling iterator of tuples

[HaloFour]

Version Used: http://tryroslyn.azurewebsites.net/ (master Oct 29 2016)

Steps to Reproduce:

using System;
using System.Collections.Generic;

public class C {
    public IEnumerable<(int, int)> entries() {
        yield return (1, 2);
    }
}

Expected Behavior:

Compiles successfully.

Actual Behavior:

Unexpected value 'NoConversion' of type 'Microsoft.CodeAnalysis.CSharp.ConversionKind'
   at Microsoft.CodeAnalysis.CSharp.CodeGen.CodeGenerator.EmitConversion(BoundConversion conversion) in D:\#TeamCity\buildAgent\work\596e688e8f7f38c8\!roslyn\dotnet\Src\Compilers\CSharp\Portable\CodeGen\EmitConversion.cs:line 117
   at Microsoft.CodeAnalysis.CSharp.CodeGen.CodeGenerator.EmitConversionExpression(BoundConversion conversion, Boolean used) in D:\#TeamCity\buildAgent\work\596e688e8f7f38c8\!roslyn\dotnet\Src\Compilers\CSharp\Portable\CodeGen\EmitConversion.cs:line 34
   at Microsoft.CodeAnalysis.CSharp.CodeGen.CodeGenerator.EmitExpressionCore(BoundExpression expression, Boolean used) in D:\#TeamCity\buildAgent\work\596e688e8f7f38c8\!roslyn\dotnet\Src\Compilers\CSharp\Portable\CodeGen\EmitExpression.cs:line 112
   at Microsoft.CodeAnalysis.CSharp.CodeGen.CodeGenerator.EmitExpressionCoreWithStackGuard(BoundExpression expression, Boolean used) in D:\#TeamCity\buildAgent\work\596e688e8f7f38c8\!roslyn\dotnet\Src\Compilers\CSharp\Portable\CodeGen\EmitExpression.cs:line 72
   at Microsoft.CodeAnalysis.CSharp.CodeGen.CodeGenerator.EmitExpression(BoundExpression expression, Boolean used) in D:\#TeamCity\buildAgent\work\596e688e8f7f38c8\!roslyn\dotnet\Src\Compilers\CSharp\Portable\CodeGen\EmitExpression.cs:line 60
   at Microsoft.CodeAnalysis.CSharp.CodeGen.CodeGenerator.EmitReturnStatement(BoundReturnStatement boundReturnStatement) in D:\#TeamCity\buildAgent\work\596e688e8f7f38c8\!roslyn\dotnet\Src\Compilers\CSharp\Portable\CodeGen\EmitStatement.cs:line 684
   at Microsoft.CodeAnalysis.CSharp.CodeGen.CodeGenerator.EmitStatement(BoundStatement statement) in D:\#TeamCity\buildAgent\work\596e688e8f7f38c8\!roslyn\dotnet\Src\Compilers\CSharp\Portable\CodeGen\EmitStatement.cs:line 44
   at Microsoft.CodeAnalysis.CSharp.CodeGen.CodeGenerator.EmitBlock(BoundBlock block) in D:\#TeamCity\buildAgent\work\596e688e8f7f38c8\!roslyn\dotnet\Src\Compilers\CSharp\Portable\CodeGen\EmitStatement.cs:line 614
   at Microsoft.CodeAnalysis.CSharp.CodeGen.CodeGenerator.EmitStatement(BoundStatement statement) in D:\#TeamCity\buildAgent\work\596e688e8f7f38c8\!roslyn\dotnet\Src\Compilers\CSharp\Portable\CodeGen\EmitStatement.cs:line 24
   at Microsoft.CodeAnalysis.CSharp.CodeGen.CodeGenerator.GenerateImpl() in D:\#TeamCity\buildAgent\work\596e688e8f7f38c8\!roslyn\dotnet\Src\Compilers\CSharp\Portable\CodeGen\CodeGenerator.cs:line 248
   at Microsoft.CodeAnalysis.CSharp.CodeGen.CodeGenerator.Generate() in D:\#TeamCity\buildAgent\work\596e688e8f7f38c8\!roslyn\dotnet\Src\Compilers\CSharp\Portable\CodeGen\CodeGenerator.cs:line 183
   at Microsoft.CodeAnalysis.CSharp.MethodCompiler.GenerateMethodBody(PEModuleBuilder moduleBuilder, MethodSymbol method, Int32 methodOrdinal, BoundStatement block, ImmutableArray`1 lambdaDebugInfo, ImmutableArray`1 closureDebugInfo, StateMachineTypeSymbol stateMachineTypeOpt, VariableSlotAllocator variableSlotAllocatorOpt, DiagnosticBag diagnostics, DebugDocumentProvider debugDocumentProvider, ImportChain importChainOpt, Boolean emittingPdb, ImmutableArray`1 dynamicAnalysisSpans) in D:\#TeamCity\buildAgent\work\596e688e8f7f38c8\!roslyn\dotnet\Src\Compilers\CSharp\Portable\Compiler\MethodCompiler.cs:line 1311
   at Microsoft.CodeAnalysis.CSharp.MethodCompiler.CompileSynthesizedMethods(TypeCompilationState compilationState) in D:\#TeamCity\buildAgent\work\596e688e8f7f38c8\!roslyn\dotnet\Src\Compilers\CSharp\Portable\Compiler\MethodCompiler.cs:line 631
   at Microsoft.CodeAnalysis.CSharp.MethodCompiler.CompileNamedType(NamedTypeSymbol containingType) in D:\#TeamCity\buildAgent\work\596e688e8f7f38c8\!roslyn\dotnet\Src\Compilers\CSharp\Portable\Compiler\MethodCompiler.cs:line 537
   at Microsoft.CodeAnalysis.CSharp.MethodCompiler.<>c__DisplayClass20_0.<CompileNamedTypeAsTask>b__0() in D:\#TeamCity\buildAgent\work\596e688e8f7f38c8\!roslyn\dotnet\Src\Compilers\CSharp\Portable\Compiler\MethodCompiler.cs:line 323
   at Roslyn.Utilities.UICultureUtilities.<>c__DisplayClass5_0.<WithCurrentUICulture>b__0() in D:\#TeamCity\buildAgent\work\596e688e8f7f38c8\!roslyn\dotnet\Src\Compilers\Core\Portable\InternalUtilities\UICultureUtilities.cs:line 136
   at System.Threading.Tasks.Task.InnerInvoke()
   at System.Threading.Tasks.Task.Execute()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.GetResult()
   at Microsoft.CodeAnalysis.CSharp.MethodCompiler.WaitForWorkers() in D:\#TeamCity\buildAgent\work\596e688e8f7f38c8\!roslyn\dotnet\Src\Compilers\CSharp\Portable\Compiler\MethodCompiler.cs:line 238
   at Microsoft.CodeAnalysis.CSharp.MethodCompiler.CompileMethodBodies(CSharpCompilation compilation, PEModuleBuilder moduleBeingBuiltOpt, Boolean generateDebugInfo, Boolean hasDeclarationErrors, DiagnosticBag diagnostics, Predicate`1 filterOpt, CancellationToken cancellationToken) in D:\#TeamCity\buildAgent\work\596e688e8f7f38c8\!roslyn\dotnet\Src\Compilers\CSharp\Portable\Compiler\MethodCompiler.cs:line 137
   at Microsoft.CodeAnalysis.CSharp.CSharpCompilation.CompileMethods(CommonPEModuleBuilder moduleBuilder, Boolean emittingPdb, DiagnosticBag diagnostics, Predicate`1 filterOpt, CancellationToken cancellationToken) in D:\#TeamCity\buildAgent\work\596e688e8f7f38c8\!roslyn\dotnet\Src\Compilers\CSharp\Portable\Compilation\CSharpCompilation.cs:line 2335
   at Microsoft.CodeAnalysis.Compilation.Emit(Stream peStream, Stream pdbStream, Stream xmlDocumentationStream, Stream win32Resources, IEnumerable`1 manifestResources, EmitOptions options, IMethodSymbol debugEntryPoint, Stream sourceLinkStream, IEnumerable`1 embeddedTexts, CompilationTestData testData, CancellationToken cancellationToken) in D:\#TeamCity\buildAgent\work\596e688e8f7f38c8\!roslyn\dotnet\Src\Compilers\Core\Portable\Compilation\Compilation.cs:line 2016
   at Microsoft.CodeAnalysis.Compilation.Emit(Stream peStream, Stream pdbStream, Stream xmlDocumentationStream, Stream win32Resources, IEnumerable`1 manifestResources, EmitOptions options, IMethodSymbol debugEntryPoint, Stream sourceLinkStream, IEnumerable`1 embeddedTexts, CancellationToken cancellationToken) in D:\#TeamCity\buildAgent\work\596e688e8f7f38c8\!roslyn\dotnet\Src\Compilers\Core\Portable\Compilation\Compilation.cs:line 1964
   at TryRoslyn.Core.Processing.CodeProcessor.Process(String code, ProcessingOptions options) in D:\#TeamCity\buildAgent\work\596e688e8f7f38c8\!sites\dotnet-master\Core\Processing\CodeProcessor.cs:line 44
   at TryRoslyn.Web.Api.Controllers.RoslynController.Compilation(CompilationArguments arguments) in D:\#TeamCity\buildAgent\work\596e688e8f7f38c8\!sites\dotnet-master\Web.Api\Controllers\RoslynController.cs:line 18
   at lambda_method(Closure , Object , Object[] )
   at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.<>c__DisplayClass10.<GetExecutor>b__9(Object instance, Object[] methodParameters)
   at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.Execute(Object instance, Object[] arguments)
   at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ExecuteAsync(HttpControllerContext controllerContext, IDictionary`2 arguments, CancellationToken cancellationToken)
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Tracing.ITraceWriterExtensions.<TraceBeginEndAsyncCore>d__18`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Controllers.ApiControllerActionInvoker.<InvokeActionAsyncCore>d__0.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Tracing.ITraceWriterExtensions.<TraceBeginEndAsyncCore>d__18`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Controllers.ActionFilterResult.<ExecuteAsync>d__2.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Tracing.Tracers.HttpControllerTracer.<ExecuteAsyncCore>d__5.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Tracing.ITraceWriterExtensions.<TraceBeginEndAsyncCore>d__18`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Dispatcher.HttpControllerDispatcher.<SendAsync>d__1.MoveNext()

[AlekseyTs]

It looks like the issue has been already addressed by #15048