[Lldb-commits] [lldb] [lldb] Make SBType::FindDirectNestedType work with expression ASTs (PR #89183)

[Michael Buch via lldb-commits]

Michael137 wrote:

> > One thing I'd like to get feedback on is whether this should be looking into base classes. The discussion on the original PR focuses on lexically nested types, but going through base classes (following usual language rules) is another form of nesting. Both the existing and the new implementations don't do that, but I think it would be more natural to do it. Of course, then the function can definitely return more than one result...
> 
> What you're describing here is in line with member lookup described in the Standard. While it might be a useful facility, it's at odds with the intent of `FindDirectNestedTypes()` to be a small building block for efficient AST traversal. For the use case I have for this function, any amount of lookup is going to regress the performance of the formatter, and subsequently responsiveness of the debugger. So if you're going to pursue this, I suggest exposing this as a new function.

I don't expect the simple `DeclContext` lookup proposed here to be expensive. What *is* expensive from the data-formatters point of view is either full-blown expression evaluation or a global search in DWARF for some type.

Re. looking at base classes, don't have a strong opinion on it. There's some precedent for looking at base classes already in `TypeSystemClang` (e.g., `GetIndexOfChildWithName`). But as you say @labath, that would require an API change

https://github.com/llvm/llvm-project/pull/89183