[PATCH] D128372: [Clang-Tidy] Empty Check

[Christopher Di Bella via Phabricator via cfe-commits]

cjdb added inline comments.


================
Comment at: clang-tools-extra/clang-tidy/bugprone/StandaloneEmptyCheck.cpp:177-178
+      diag(NonMemberLoc, "ignoring the result of '%0', did you mean 'clear()'?")
+          << llvm::dyn_cast<NamedDecl>(NonMemberCall->getCalleeDecl())
+                 ->getQualifiedNameAsString()
+          << FixItHint::CreateReplacement(ReplacementRange, ReplacementText);
----------------
abrahamcd wrote:
> njames93 wrote:
> > Diagnostics can accept args as `const NamedDecl *`, so you can omit the call to `getQualifiedNameAsString()`.
> > The use of `dyn_cast` here is suspicious. If the CalleeDecl isn't a `NamedDecl`, this would assert when you try and call `getQualifiedNameAsString`, but equally I can't see any case why the CalleeDecl wouldn't be a `NamedDecl`. @rsmith Can you think of any situation where this could happen?
> Seems that without `getQualifiedNameAsString()` I get longer less-readable versions of the name, e.g. `'empty<std::vector<int> &>'` instead of just `'std::empty'`. Do you think the extra information is helpful here?
I'm partial to `'std::empty'` because that's presumably what the user will type, and so it'll be easier for them to understand. `'empty<std::vector<int> &>'` isn't useful because we almost always defer to type deduction.


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Comment at: clang-tools-extra/clang-tidy/bugprone/StandaloneEmptyCheck.cpp:57-72
+  using ast_matchers::callee;
+  using ast_matchers::callExpr;
+  using ast_matchers::cxxMemberCallExpr;
+  using ast_matchers::cxxMethodDecl;
+  using ast_matchers::expr;
+  using ast_matchers::functionDecl;
+  using ast_matchers::hasName;
----------------
njames93 wrote:
> These using declarations are annoying, the common convention in tidy checks is to just use a global `using namespace ast_matchers` at the top of the file.
Adding them just after the namespaces are opened would be good.

I've had issues with refactoring llvm-project files in the past that have global //using-directives//, so I'd prefer it if we stuck with the //using-declarations// please. If they're a part of the preamble, they become additional lines that will be scrolled over.


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Comment at: clang-tools-extra/clang-tidy/bugprone/StandaloneEmptyCheck.cpp:120-121
+        llvm::find_if(Methods, [](const CXXMethodDecl *F) {
+          return F->getDeclName().getAsString() == "clear" &&
+                 F->getMinRequiredArguments() == 0;
+        });
----------------
njames93 wrote:
> We also need to check qualifiers. If there exists a clear method but its unavailable due to it not being const when our member is const. The fix would result in a compile error.
Good catch. We probably shouldn't be suggesting `clear()` on a const object anyway.


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  https://reviews.llvm.org/D128372/new/

https://reviews.llvm.org/D128372