Fixing TypeInferrer crash with `return` or `yield return` as a global statement

src/EditorFeatures/CSharpTest/TypeInferrer/TypeInferrerTests.cs

@@ -1096,6 +1096,13 @@ IEnumerable<int> F()
             await TestAsync(markup, "global::System.Int32");
         }
 
+        [Fact, Trait(Traits.Feature, Traits.Features.TypeInferenceService)]
+        public async Task TestYieldReturnAsGlobalStatement()
+        {
+            await TestAsync(
+@"yield return [|abc|]", "global::System.Object", sourceCodeKind: SourceCodeKind.Script);
+        }
+
         [Fact, Trait(Traits.Feature, Traits.Features.TypeInferenceService)]
         public async Task TestReturnInSimpleLambda()
         {
@@ -1219,6 +1226,13 @@ public async Task TestReturnInAsyncVoidAnonymousMethod()
 };", "void");
         }
 
+        [Fact, Trait(Traits.Feature, Traits.Features.TypeInferenceService)]
+        public async Task TestReturnAsGlobalStatement()
+        {
+            await TestAsync(
+@"return [|Goo()|];", "global::System.Object", sourceCodeKind: SourceCodeKind.Script);
+        }
+
         [Fact, Trait(Traits.Feature, Traits.Features.TypeInferenceService)]
         public async Task TestSimpleLambda()
         {

src/EditorFeatures/TestUtilities/TypeInferrer/TypeInferrerTestBase.cs

@@ -37,18 +37,19 @@ private static async Task<bool> CanUseSpeculativeSemanticModelAsync(Document doc
             return !service.GetMemberBodySpanForSpeculativeBinding(node).IsEmpty;
         }
 
-        protected async Task TestAsync(string text, string expectedType, bool testNode = true, bool testPosition = true)
+        protected async Task TestAsync(string text, string expectedType, bool testNode = true, bool testPosition = true,
+            SourceCodeKind sourceCodeKind = SourceCodeKind.Regular)
         {
             MarkupTestFile.GetSpan(text.NormalizeLineEndings(), out text, out var textSpan);
 
             if (testNode)
             {
-                await TestWithAndWithoutSpeculativeSemanticModelAsync(text, textSpan, expectedType, useNodeStartPosition: false);
+                await TestWithAndWithoutSpeculativeSemanticModelAsync(text, textSpan, expectedType, useNodeStartPosition: false, sourceCodeKind);
             }
 
             if (testPosition)
             {
-                await TestWithAndWithoutSpeculativeSemanticModelAsync(text, textSpan, expectedType, useNodeStartPosition: true);
+                await TestWithAndWithoutSpeculativeSemanticModelAsync(text, textSpan, expectedType, useNodeStartPosition: true, sourceCodeKind);
             }
         }
 
@@ -56,14 +57,15 @@ protected async Task TestAsync(string text, string expectedType, bool testNode =
             string text,
             TextSpan textSpan,
             string expectedType,
-            bool useNodeStartPosition)
+            bool useNodeStartPosition,
+            SourceCodeKind sourceCodeKind)
         {
-            var document = fixture.UpdateDocument(text, SourceCodeKind.Regular);
+            var document = fixture.UpdateDocument(text, sourceCodeKind);
             await TestWorkerAsync(document, textSpan, expectedType, useNodeStartPosition);
 
             if (await CanUseSpeculativeSemanticModelAsync(document, textSpan.Start))
             {
-                var document2 = fixture.UpdateDocument(text, SourceCodeKind.Regular, cleanBeforeUpdate: false);
+                var document2 = fixture.UpdateDocument(text, sourceCodeKind, cleanBeforeUpdate: false);
                 await TestWorkerAsync(document2, textSpan, expectedType, useNodeStartPosition);
             }
         }

src/Workspaces/CSharp/Portable/LanguageServices/CSharpTypeInferenceService.TypeInferrer.cs

@@ -1869,7 +1869,9 @@ private ISymbol GetDeclaredMemberSymbolFromOriginalSemanticModel(SyntaxNode decl
                     return originalSemanticModel.GetDeclaredSymbol(declaration, CancellationToken);
                 }
 
-                return currentSemanticModel.GetDeclaredSymbol(declarationInCurrentTree, CancellationToken);
+                return declarationInCurrentTree != null
+                    ? currentSemanticModel.GetDeclaredSymbol(declarationInCurrentTree, CancellationToken)
+                    : null;
             }
 
             private IEnumerable<TypeInferenceInfo> InferTypeInSwitchLabel(