[clang-tools-extra] [clangd] Avoid invalid include-fixer fuzzy-find queries (PR #212134)

[Macro Terra via cfe-commits]

hongtaihu wrote:

> > Investigated this further. `DeclarationNameInfo` is correct here: parser recognizes `operator ::align_val_t` as a conversion-function-id, and Sema constructs a `CXXConversionFunctionName` with a target type.
> > The incorrect step was in `UnresolvedNameRecorder`: it unconditionally called `Typo.getAsString()` and treated the diagnostic presentation string as `UnresolvedName::Name`. For this kind, that string contains the target type and can contain `std::`, which is not an outer lookup scope that IncludeFixer can split into `Name + Scopes`.
> > I updated the patch to reject only `CXXConversionFunctionName` before this lossy conversion. This removes the string-based `contains("::")` check. I intentionally do not reject all non-identifier names: e.g. overloaded operators may still be valid unqualified index names.
> 
> I’m not sure it’s right to always reject `CXXConversionFunctionName`.
> 
> E.g. `test.h`
> 
> ```c++
> #pragma once
> struct Something { int I = 0; };
> ```
> 
> `test.cpp`
> 
> ```c++
> struct Wrapper {
>     template <typename T>
>     operator T() const { return T(); }
> };
> 
> void f() {
>     Wrapper W;
>     auto V =  W.operator::Something(); 
> }
> ```
> 
> test.cpp will have compilation error, which can be fixed with test.h include. So, the question is, will we reject such a case with this patch or not?

I have changed the condition.
Now it only rejects `CXXConversionFunctionName`.

https://github.com/llvm/llvm-project/pull/212134