From b59f625085e9d05055b99a03571792216f64e769 Mon Sep 17 00:00:00 2001
From: Chris Sienkiewicz <chsienki@microsoft.com>
Date: Wed, 12 Jun 2019 11:56:28 -0700
Subject: [PATCH] Dont try and check tuple conversions in error cases: (#36188)

* Dont try and check tuple conversions in error cases:
- When checking an identity converison, also check for a bound tuple if the type isn't a tuple as we might have a bound tuple with an error type
- When checking a tuple conversion, don't GenerateConversion in the error case as we don't have a target type to generate against
- Update tests
---
 .../Portable/FlowAnalysis/NullableWalker.cs     |  4 ++--
 .../Semantics/NullableReferenceTypesTests.cs    | 17 +++++++++++++++--
 .../NameTupleElement/NameTupleElementTests.cs   |  4 +++-
 3 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/src/Compilers/CSharp/Portable/FlowAnalysis/NullableWalker.cs b/src/Compilers/CSharp/Portable/FlowAnalysis/NullableWalker.cs
index 3a8d05bf62d..080982a0117 100644
--- a/src/Compilers/CSharp/Portable/FlowAnalysis/NullableWalker.cs
+++ b/src/Compilers/CSharp/Portable/FlowAnalysis/NullableWalker.cs
@@ -4447,7 +4447,7 @@ private static BoundConversion GetConversionIfApplicable(BoundExpression convers
                             return operandType;
                         }
                     }
-                    if (operandType.Type?.IsTupleType == true)
+                    if (operandType.Type?.IsTupleType == true || conversionOperand.Kind == BoundKind.TupleLiteral)
                     {
                         goto case ConversionKind.ImplicitTuple;
                     }
@@ -4550,7 +4550,7 @@ private static BoundConversion GetConversionIfApplicable(BoundExpression convers
                         }
                     }
 
-                    if (checkConversion)
+                    if (checkConversion && !targetType.IsErrorType())
                     {
                         // https://github.com/dotnet/roslyn/issues/29699: Report warnings for user-defined conversions on tuple elements.
                         conversion = GenerateConversion(_conversions, conversionOperand, operandType.Type, targetType, fromExplicitCast, extensionMethodThisArgument);
diff --git a/src/Compilers/CSharp/Test/Semantic/Semantics/NullableReferenceTypesTests.cs b/src/Compilers/CSharp/Test/Semantic/Semantics/NullableReferenceTypesTests.cs
index 86081cb4c5d..f65d407093d 100644
--- a/src/Compilers/CSharp/Test/Semantic/Semantics/NullableReferenceTypesTests.cs
+++ b/src/Compilers/CSharp/Test/Semantic/Semantics/NullableReferenceTypesTests.cs
@@ -51919,7 +51919,8 @@ static void F(object? x, object? y)
                 Diagnostic(ErrorCode.WRN_NullReferenceReceiver, "t.Rest.Item2").WithLocation(11, 13));
         }
 
-        [Fact(Skip = "https://github.com/dotnet/roslyn/issues/35157")]
+        [Fact]
+        [WorkItem(35157, "https://github.com/dotnet/roslyn/issues/35157")]
         public void TupleTypeInference_08()
         {
             var source =
@@ -51929,11 +51930,23 @@ class C
     void M()
     {
         _ = (null, 2);
+        _ = (null, (2, 3));
+        _ = (null, (null, (2, 3)));
     }
 }";
 
             var comp = CreateCompilation(source, options: WithNonNullTypesTrue());
-            comp.VerifyDiagnostics();
+            comp.VerifyDiagnostics(
+                // (6,9): error CS8183: Cannot infer the type of implicitly-typed discard.
+                //         _ = (null, 2);
+                Diagnostic(ErrorCode.ERR_DiscardTypeInferenceFailed, "_").WithLocation(6, 9),
+                // (7,9): error CS8183: Cannot infer the type of implicitly-typed discard.
+                //         _ = (null, (2, 3));
+                Diagnostic(ErrorCode.ERR_DiscardTypeInferenceFailed, "_").WithLocation(7, 9),
+                // (8,9): error CS8183: Cannot infer the type of implicitly-typed discard.
+                //         _ = (null, (null, (2, 3)));
+                Diagnostic(ErrorCode.ERR_DiscardTypeInferenceFailed, "_").WithLocation(8, 9)
+                );
         }
 
         [Fact]
diff --git a/src/EditorFeatures/CSharpTest/NameTupleElement/NameTupleElementTests.cs b/src/EditorFeatures/CSharpTest/NameTupleElement/NameTupleElementTests.cs
index 3d79f05afae..186168c736d 100644
--- a/src/EditorFeatures/CSharpTest/NameTupleElement/NameTupleElementTests.cs
+++ b/src/EditorFeatures/CSharpTest/NameTupleElement/NameTupleElementTests.cs
@@ -5,6 +5,7 @@
 using Microsoft.CodeAnalysis.CSharp.NameTupleElement;
 using Microsoft.CodeAnalysis.Editor.CSharp.UnitTests.CodeRefactorings;
 using Microsoft.CodeAnalysis.Test.Utilities;
+using Roslyn.Test.Utilities;
 using Xunit;
 
 namespace Microsoft.CodeAnalysis.Editor.CSharp.UnitTests.NameTupleElement
@@ -85,7 +86,8 @@ public async Task TestInCall_FirstElement_AlreadyNamed()
             await TestMissingAsync(@"class C { void M((int arg1, int arg2) x) => M(([||]arg1: 1, 2)); }");
         }
 
-        [Fact(Skip = "https://github.com/dotnet/roslyn/issues/35157")]
+        [Fact]
+        [WorkItem(35157, "https://github.com/dotnet/roslyn/issues/35157")]
         public async Task TestUntypedTuple()
         {
             await TestMissingAsync(
-- 
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