From 599022844406d0d3fe32f97d5f5d9e6a8d21b103 Mon Sep 17 00:00:00 2001
From: Charles Stoner <chucks@microsoft.com>
Date: Thu, 20 Feb 2020 10:13:16 -0800
Subject: [PATCH] Avoid use-site diagnostics in TupleTypeDecoder (#41701)

---
 .../Symbols/Metadata/PE/TupleTypeDecoder.cs   |  6 ++--
 .../Test/Emit/CodeGen/CodeGenTupleTest.cs     | 30 +++++++++++++++++
 .../Symbols/Metadata/PE/TupleTypeDecoder.vb   |  5 +--
 .../Test/Emit/CodeGen/CodeGenTuples.vb        | 33 +++++++++++++++++++
 4 files changed, 66 insertions(+), 8 deletions(-)

diff --git a/src/Compilers/CSharp/Portable/Symbols/Metadata/PE/TupleTypeDecoder.cs b/src/Compilers/CSharp/Portable/Symbols/Metadata/PE/TupleTypeDecoder.cs
index c21c0b38afe34..b7c9864af2b2c 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Metadata/PE/TupleTypeDecoder.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Metadata/PE/TupleTypeDecoder.cs
@@ -159,11 +159,9 @@ private TypeSymbol DecodeType(TypeSymbol type)
             switch (type.Kind)
             {
                 case SymbolKind.ErrorType:
-                    if (type.HasUseSiteError)
-                    {
-                        _foundUsableErrorType = true;
-                    }
+                    _foundUsableErrorType = true;
                     return type;
+
                 case SymbolKind.DynamicType:
                 case SymbolKind.TypeParameter:
                 case SymbolKind.PointerType:
diff --git a/src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenTupleTest.cs b/src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenTupleTest.cs
index b9055d66ba376..6e3ddede3389d 100644
--- a/src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenTupleTest.cs
+++ b/src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenTupleTest.cs
@@ -26095,6 +26095,36 @@ public static void Main()
             CompileAndVerify(executeComp, expectedOutput: "ran");
         }
 
+        [Fact]
+        [WorkItem(41699, "https://github.com/dotnet/roslyn/issues/41699")]
+        public void MissingBaseType_TupleTypeArgumentWithNames()
+        {
+            var sourceA =
+@"public class A<T> { }";
+            var comp = CreateCompilation(sourceA, assemblyName: "A");
+            var refA = comp.EmitToImageReference();
+
+            var sourceB =
+@"public class B : A<(object X, B Y)> { }";
+            comp = CreateCompilation(sourceB, references: new[] { refA });
+            var refB = comp.EmitToImageReference();
+
+            var sourceC =
+@"class Program
+{
+    static void Main()
+    {
+        var b = new B();
+        b.ToString();
+    }
+}";
+            comp = CreateCompilation(sourceC, references: new[] { refB });
+            comp.VerifyDiagnostics(
+                // (6,11): error CS0012: The type 'A<>' is defined in an assembly that is not referenced. You must add a reference to assembly 'A, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'.
+                //         b.ToString();
+                Diagnostic(ErrorCode.ERR_NoTypeDef, "ToString").WithArguments("A<>", "A, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null").WithLocation(6, 11));
+        }
+
         [Fact]
         [WorkItem(21727, "https://github.com/dotnet/roslyn/issues/21727")]
         public void FailedDecodingOfTupleNamesWhenMissingValueTupleType()
diff --git a/src/Compilers/VisualBasic/Portable/Symbols/Metadata/PE/TupleTypeDecoder.vb b/src/Compilers/VisualBasic/Portable/Symbols/Metadata/PE/TupleTypeDecoder.vb
index 14ea3d2bac61e..b8a4abba2c2b3 100644
--- a/src/Compilers/VisualBasic/Portable/Symbols/Metadata/PE/TupleTypeDecoder.vb
+++ b/src/Compilers/VisualBasic/Portable/Symbols/Metadata/PE/TupleTypeDecoder.vb
@@ -126,10 +126,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols.Metadata.PE
         Private Function DecodeType(type As TypeSymbol) As TypeSymbol
             Select Case type.Kind
                 Case SymbolKind.ErrorType
-
-                    If type.GetUseSiteErrorInfo() IsNot Nothing Then
-                        _foundUsableErrorType = True
-                    End If
+                    _foundUsableErrorType = True
                     Return type
 
                 Case SymbolKind.DynamicType,
diff --git a/src/Compilers/VisualBasic/Test/Emit/CodeGen/CodeGenTuples.vb b/src/Compilers/VisualBasic/Test/Emit/CodeGen/CodeGenTuples.vb
index d34d3cbd951aa..7af45489db9cf 100644
--- a/src/Compilers/VisualBasic/Test/Emit/CodeGen/CodeGenTuples.vb
+++ b/src/Compilers/VisualBasic/Test/Emit/CodeGen/CodeGenTuples.vb
@@ -22800,6 +22800,39 @@ End Class
 
         End Sub
 
+        <Fact>
+        <WorkItem(41699, "https://github.com/dotnet/roslyn/issues/41699")>
+        Public Sub MissingBaseType_TupleTypeArgumentWithNames()
+            Dim sourceA =
+"Public Class A(Of T)
+End Class"
+            Dim comp = CreateCompilation(sourceA, assemblyName:="A")
+            Dim refA = comp.EmitToImageReference()
+
+            Dim sourceB =
+"Public Class B
+    Inherits A(Of (X As Object, Y As B))
+End Class"
+            comp = CreateCompilation(sourceB, references:={refA})
+            Dim refB = comp.EmitToImageReference()
+
+            Dim sourceC =
+"Module Program
+    Sub Main()
+        Dim b = New B()
+        b.ToString()
+    End Sub
+End Module"
+            comp = CreateCompilation(sourceC, references:={refB})
+            comp.AssertTheseDiagnostics(
+"BC30456: 'ToString' is not a member of 'B'.
+        b.ToString()
+        ~~~~~~~~~~
+BC30652: Reference required to assembly 'A, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null' containing the type 'A(Of )'. Add one to your project.
+        b.ToString()
+        ~~~~~~~~~~")
+        End Sub
+
         <Fact>
         <WorkItem(41207, "https://github.com/dotnet/roslyn/issues/41207")>
         <WorkItem(1056281, "https://dev.azure.com/devdiv/DevDiv/_workitems/edit/1056281")>