[PATCH] D80800: Add an option to fully qualify classes and structs.

[Jean-Baptiste Lespiau via Phabricator via cfe-commits]

jblespiau marked an inline comment as done.
jblespiau added a comment.

I did spend a few hours, just building and finding how to run tests :(

I have a few additional questions, as I do not really understand what happen. In my initial idea, I wanted to modify the way QualType are printed, not really declarations, but I feel the logic is duplicated somewhere, and that both NamedDecl and Type are implementing the logic.



================
Comment at: clang/lib/AST/TypePrinter.cpp:326
+  if (Policy.FullyQualifiedName && Policy.GlobalScopeQualifiedName &&
+      T->isStructureOrClassType()) {
+    OS << "::";
----------------
sammccall wrote:
> structure-or-class-type isn't quite the right check:
>  - enums and typedefs for instance should also be qualified.
>  - you're looking through sugar to the underlying type, which may not be what you want
>  
> It's going to be hard to get this right from here... I suspect it's better to fix where `FullyQualifiedName` is checked in DeclPrinter.
> This ultimately calls through to NamedDecl::printNestedNameSpecifier, which is probably the right place to respect this option.
> (I don't totally understand what's meant to happen if SuppressScope is false but FullyQualiifedName is also false, that calls through to NestedNameSpecifier::print which you may want to also fix, or not)
There are several elements I do not understand (as you will see, I am completely lost).

1. I am trying to modify QualType::getAsString, and you suggest changing NamecDecl. I do not understand the relationship between Qualtype and NameDecl: I understand declaration within the context of C++:
https://www.dummies.com/programming/cpp/expressions-and-declarations-in-c-programming/
Thus, a Declaration will be made of several parts, some of which will be Type. Thus, for me, the change should not be in NameDecl but in Type, to also make sure the change is there both when we print a NameDecl and a type.. If we modify NameDecl, then, when printing a type through Type::getAsString, we won't get the global "::" specifier.
I have understood NamedDecl::printQualifiedName calls NamedDecl::printNestedNameSpecifier which calls the Type::print function, see
https://github.com/llvm-mirror/clang/blob/master/lib/AST/Decl.cpp#L1630

=> From that, I still understand I should modify how types are printed, not NamedDecl. I may completely be incorrect, and I am only looking to understand.

Thus, I feel my change is correcly placed, but we can change it to be:

  if (!Policy.SuppressScope && Policy.GlobalScopeQualifiedName &&
      (T->isStructureOrClassType() || T->isEnumeralType() ||
       isa<TypedefType>(T))) {
    OS << "::";
  }

Other remarks:
2. As documented:
```
  /// When true, print the fully qualified name of function declarations.
  /// This is the opposite of SuppressScope and thus overrules it.
  unsigned FullyQualifiedName : 1;
```

 FullyQualifiedName is only controlling the fully-qualification of functions.
https://github.com/llvm/llvm-project/blob/a2a3e9f0a6e91103a0d1fa73086dbdf109c48f69/clang/lib/AST/DeclPrinter.cpp#L625

So I do not think we have to follow this.

I think it is `SuppressScope` which controls whether it is fully qualified or not,:
https://github.com/llvm/llvm-project/blob/a2a3e9f0a6e91103a0d1fa73086dbdf109c48f69/clang/lib/AST/DeclPrinter.cpp#L629

If Policy.SuppressScope is False, then I understand it's fully qualified.

3. "you're looking through sugar to the underlying type, which may not be what you want": I do not understand "sugar" in that context. I have read this name in the code in clang, but still, I do not understand it. I only know https://en.wikipedia.org/wiki/Syntactic_sugar, which does not seem to apply here (Obviously, I am not a native English speaker).

For the testing:

Building and running
------------------------

After > 90minutes of building with:
cmake -DLLVM_ENABLE_PROJECTS=clang -G "Unix Makefiles" ../llvm
make check-clang

It took me quite a while to find how to execute a single test file:

~/llvm-project/build/tools/clang/unittests/AST]
└──╼ make -j12 ASTTests && ./ASTTests --gtest_filter=NamedDeclPrinter*

did the job. 

- NamedDeclPrinterTest.cpp  feels strange for the tests, as what I am modifying is not NamedDecl, but Qualtype::getAsString. But given there is no TypeTest.cpp, maybe it's best location.


I must admit that I am struggling a lot to understand both the execution flow and the code itself :(



CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D80800/new/

https://reviews.llvm.org/D80800