[PATCH] D24349: [clang-tidy] Extend readability-container-size-empty to arbitrary class with size() and empty()

[Aaron Ballman via cfe-commits]

aaron.ballman added a comment.

In https://reviews.llvm.org/D24349#537350, @Eugene.Zelenko wrote:

> Probably check should have options to extend list of containers and also to assume all classes with integer type size() const and bool empty() const as containers. It may be not trivial to find out all custom containers and last option will be helpful to assemble such list.


I think this should actually have two options: one is a list of default-checked containers (default is the list of STL containers we previously had), and the other is a Boolean option for guessing at what might be a container based on function signature (default is true). This gives people a way to silence the diagnostic while still being useful. I would document what function signatures we use as our heuristic, but note that the function signatures we care about may change (for instance, we may decide that const-qualification is unimportant, or that we want to require begin()/end() functions, etc). I think `<standard integer type> size() const` and `bool empty() const` are a reasonable heuristic for a first pass.


================
Comment at: clang-tidy/readability/ContainerSizeEmptyCheck.cpp:33
@@ +32,3 @@
+  const auto validContainer = namedDecl(
+      has(functionDecl(
+          isPublic(), hasName("size"), returns(isInteger()),
----------------
omtcyfz wrote:
> Thank you!
> 
> Blacklisted these types.
> 
> Actually, I believe if someone has `bool size()` in their codebase there's still a problem...
> Blacklisted these types.

I'm still not certain this is correct. For instance, if someone wants to do `uint8_t size() const;`, we shouldn't punish them because `uint8_t` happens to be `unsigned char` for their platform. But you are correct that we don't want this to work with char32_t, for instance.

I think the best approach is to make a local matcher for the type predicate. We want isInteger() unless it's char (that's not explicitly qualified with signed or unsigned), bool, wchar_t, char16_t, char32_t, or an enumeration type.

> Actually, I believe if someone has bool size() in their codebase there's still a problem...

Agreed, though not as part of this check. ;-)


https://reviews.llvm.org/D24349