Create extended-nameof-scope.md

proposals/extended-nameof-scope.md

@@ -0,0 +1,26 @@
+# Extended `nameof` scope
+
+## Summary
+
+Allow `nameof(parameter)` inside an attribute on a method or parameter.
+For example:
+- `[MyAttribute(nameof(parameter))] void M(int parameter) { }`
+- `[MyAttribute(nameof(TParameter))] void M<TParameter>() { }`
+- `void M(int parameter, [MyAttribute(nameof(parameter))] int other) { }`
+
+## Motivation
+
+Attributes like `NotNullWhen` or `CallerExpression` need to refer to parameters, but those parameters are currently not in scope.
+
+## Detailed design
+
+TODO
+
+[Method parameters](https://github.com/dotnet/csharplang/blob/master/spec/classes.md#method-parameters)
+
+[Simple names](https://github.com/dotnet/csharplang/blob/master/spec/expressions.md#simple-names)
+
+[Scopes](https://github.com/dotnet/csharplang/blob/master/spec/basic-concepts.md#scopes)
+
+## Related spec sections
+- [Corresponding parameters](https://github.com/dotnet/csharplang/blob/master/spec/expressions.md#corresponding-parameters)