Bail in GetDependenceChain if typesymbol isn't found (#10331)

harden both DetectTypeCircularity and GetDependenceChain

src/Compilers/CSharp/Test/Symbol/Compilation/SemanticModelAPITests.cs

@@ -2101,6 +2101,32 @@ void M(int x)
             VerifySpeculativeSemanticModelForMethodBody(blockStatement, speculativeModel);
         }
 
+        [Fact()]
+        [WorkItem(10211, "https://github.com/dotnet/roslyn/issues/10211")]
+        public void GetDependenceChainRegression_10211_working()
+        {
+            var compilation = CreateCompilation(@"
+class Parent {}
+class Child : Parent {}
+");
+            var semanticModel = compilation.GetSemanticModel(compilation.SyntaxTrees[0]);
+            // Ensure that we don't crash here.
+            semanticModel.GetMethodBodyDiagnostics();
+        }
+
+        [Fact()]
+        [WorkItem(10211, "https://github.com/dotnet/roslyn/issues/10211")]
+        public void GetDependenceChainRegression_10211()
+        {
+            var compilation = CreateCompilation(@"
+class Child : Parent {}
+class Parent {}
+");
+            var semanticModel = compilation.GetSemanticModel(compilation.SyntaxTrees[0]);
+            // Ensure that we don't crash here.
+            semanticModel.GetMethodBodyDiagnostics();
+        }
+
         private static void VerifySpeculativeSemanticModelForMethodBody(BlockSyntax blockStatement, SemanticModel speculativeModel)
         {
             var localDecl = (LocalDeclarationStatementSyntax)blockStatement.Statements[0];

src/Compilers/VisualBasic/Portable/Symbols/BaseTypeAnalysis.vb

@@ -187,10 +187,9 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
         Private Function GetDependenceChain(visited As HashSet(Of Symbol),
                                                root As SourceNamedTypeSymbol,
                                                current As TypeSymbol) As ConsList(Of DependencyDesc)
-
             Debug.Assert(root.OriginalDefinition = root, "root must not be a substitution")
 
-            If current Is Nothing Then
+            If current Is Nothing OrElse current.Kind = SymbolKind.ErrorType Then
                 Return Nothing
             End If
 

src/Compilers/VisualBasic/Portable/Symbols/Source/SourceMemberContainerTypeSymbol.vb

@@ -2230,8 +2230,12 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
                 Return True
             End If
 
+            ' We can not get the relative order of a declaration without a source location
+            If typeToTest.Locations.IsEmpty Then
+                Return True
+            End If
+
             ' We use simple comparison based on source location 
-            Debug.Assert(typeToTest.Locations.Length > 0)
             Dim typeToTestLocation = typeToTest.Locations(0)
 
             Debug.Assert(Me.Locations.Length > 0)

src/Compilers/VisualBasic/Test/Semantic/Compilation/SemanticModelAPITests.vb

@@ -4061,6 +4061,48 @@ End Class
             Assert.Equal(2, treeErrs.Length())
         End Sub
 
+        <Fact()>
+        <WorkItem(10211, "https://github.com/dotnet/roslyn/issues/10211")>
+        Public Sub GetDependenceChainRegression_10211_working()
+            Dim source = <compilation>
+                             <file name="a.vb"><![CDATA[
+                                Public Class Parent
+                                End Class
+
+                                Public Class Child
+                                    Inherits Parent
+                                End Class
+                            ]]></file>
+                         </compilation>
+
+            Dim compilation = CreateCompilationWithoutReferences(source)
+            Dim semanticModel = compilation.GetSemanticModel(compilation.SyntaxTrees(0))
+
+            ' Ensuring that this doesn't throw
+            semanticModel.GetMethodBodyDiagnostics()
+        End Sub
+
+        <Fact()>
+        <WorkItem(10211, "https://github.com/dotnet/roslyn/issues/10211")>
+        Public Sub GetDependenceChainRegression_10211()
+            Dim source = <compilation>
+                             <file name="a.vb"><![CDATA[
+                                Public Class Child
+                                    Inherits Parent
+                                End Class
+
+                                Public Class Parent
+                                End Class
+                            ]]></file>
+                         </compilation>
+
+            Dim compilation = CreateCompilationWithoutReferences(source)
+            Dim semanticModel = compilation.GetSemanticModel(compilation.SyntaxTrees(0))
+
+            ' Ensuring that this doesn't throw
+            semanticModel.GetMethodBodyDiagnostics()
+        End Sub
+
         <WorkItem(859721, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/859721")>
         <Fact()>
         Public Sub TestMethodBodyDiagnostics()