Need tests to ensure edit-and-continue works with expression-bodied methods (#20931)

src/Features/CSharp/Portable/EditAndContinue/CSharpEditAndContinueAnalyzer.cs

@@ -2519,8 +2519,8 @@ private void ClassifyUpdate(AccessorDeclarationSyntax oldNode, AccessorDeclarati
                 Debug.Assert(newNode.Parent.Parent is BasePropertyDeclarationSyntax);
 
                 ClassifyMethodBodyRudeUpdate(
-                    oldNode.Body,
-                    newNode.Body,
+                    (SyntaxNode)oldNode.Body ?? oldNode.ExpressionBody?.Expression,
+                    (SyntaxNode)newNode.Body ?? newNode.ExpressionBody?.Expression,
                     containingMethodOpt: null,
                     containingType: (TypeDeclarationSyntax)newNode.Parent.Parent.Parent);
             }
@@ -2546,8 +2546,8 @@ private void ClassifyUpdate(ConstructorDeclarationSyntax oldNode, ConstructorDec
                 }
 
                 ClassifyMethodBodyRudeUpdate(
-                    oldNode.Body,
-                    newNode.Body,
+                    (SyntaxNode)oldNode.Body ?? oldNode.ExpressionBody?.Expression,
+                    (SyntaxNode)newNode.Body ?? newNode.ExpressionBody?.Expression,
                     containingMethodOpt: null,
                     containingType: (TypeDeclarationSyntax)newNode.Parent);
             }
@@ -2555,8 +2555,8 @@ private void ClassifyUpdate(ConstructorDeclarationSyntax oldNode, ConstructorDec
             private void ClassifyUpdate(DestructorDeclarationSyntax oldNode, DestructorDeclarationSyntax newNode)
             {
                 ClassifyMethodBodyRudeUpdate(
-                    oldNode.Body,
-                    newNode.Body,
+                    (SyntaxNode)oldNode.Body ?? oldNode.ExpressionBody?.Expression,
+                    (SyntaxNode)newNode.Body ?? newNode.ExpressionBody?.Expression,
                     containingMethodOpt: null,
                     containingType: (TypeDeclarationSyntax)newNode.Parent);
             }

src/Features/CSharp/Portable/EditAndContinue/SyntaxUtilities.cs

@@ -187,7 +187,13 @@ public static SyntaxNode TryGetEffectiveGetterBody(ArrowExpressionClauseSyntax p
                 return propertyBody.Expression;
             }
 
-            return accessorList?.Accessors.Where(a => a.IsKind(SyntaxKind.GetAccessorDeclaration)).FirstOrDefault()?.Body;
+            var firstGetter = accessorList?.Accessors.Where(a => a.IsKind(SyntaxKind.GetAccessorDeclaration)).FirstOrDefault();
+            if (firstGetter == null)
+            {
+                return null;
+            }
+
+            return (SyntaxNode)firstGetter.Body ?? firstGetter.ExpressionBody?.Expression;
         }
 
         public static SyntaxTokenList? TryGetFieldOrPropertyModifiers(SyntaxNode node)