[semi-auto-props]: Disallow 'nameof(field)'

src/Compilers/CSharp/Portable/Binder/Binder_Expressions.cs

@@ -1563,6 +1563,10 @@ private BoundExpression BindIdentifier(
                         if (GetSymbolForPossibleFieldKeyword() is { } backingField)
                         {
                             expression = BindNonMethod(node, backingField, diagnostics, LookupResultKind.Viable, indexed: false, isError: false);
+                            if (IsInsideNameof)
+                            {
+                                Error(diagnostics, ErrorCode.ERR_FieldKeywordInsideNameOf, node);
+                            }
                         }
                     }
                 }

src/Compilers/CSharp/Portable/CSharpResources.resx

@@ -7001,4 +7001,7 @@ To remove the warning, you can use /reference instead (set the Embed Interop Typ
   <data name="ERR_MisplacedRecord" xml:space="preserve">
     <value>Unexpected keyword 'record'. Did you mean 'record struct' or 'record class'?</value>
   </data>
+  <data name="ERR_FieldKeywordInsideNameOf" xml:space="preserve">
+    <value>Cannot use 'field' keyword inside 'nameof' expressions.</value>
+  </data>
 </root>

src/Compilers/CSharp/Portable/Errors/ErrorCode.cs

@@ -2050,6 +2050,8 @@ internal enum ErrorCode
         ERR_NoDelegateConstraint = 9011,
         ERR_MisplacedRecord = 9012,
 
+        ERR_FieldKeywordInsideNameOf = 9013,
+
         #endregion
 
         // Note: you will need to re-generate compiler code after adding warnings (eng\generate-compiler-code.cmd)