[clang-tidy] Add `readability-container-contains` check

This commit introduces a new check `readability-container-contains` which finds
usages of `container.count()` and `container.find() != container.end()` and
instead recommends the `container.contains()` method introduced in C++20.

For containers which permit multiple entries per key (`multimap`, `multiset`,
...), `contains` is more efficient than `count` because `count` has to do
unnecessary additional work.

While this this performance difference does not exist for containers with only
a single entry per key (`map`, `unordered_map`, ...), `contains` still conveys
the intent better.

Reviewed By: xazax.hun, whisperity

Differential Revision: http://reviews.llvm.org/D112646

1 files changed, 3 insertions, 0 deletions

diff --git a/clang-tools-extra/clang-tidy/readability/ReadabilityTidyModule.cpp b/clang-tools-extra/clang-tidy/readability/ReadabilityTidyModule.cpp
index b0493d4..6bbef6b 100644
--- a/clang-tools-extra/clang-tidy/readability/ReadabilityTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/readability/ReadabilityTidyModule.cpp
@@ -12,6 +12,7 @@
 #include "AvoidConstParamsInDecls.h"
 #include "BracesAroundStatementsCheck.h"
 #include "ConstReturnTypeCheck.h"
+#include "ContainerContainsCheck.h"
 #include "ContainerDataPointerCheck.h"
 #include "ContainerSizeEmptyCheck.h"
 #include "ConvertMemberFunctionsToStatic.h"
@@ -64,6 +65,8 @@ public:
         "readability-braces-around-statements");
     CheckFactories.registerCheck<ConstReturnTypeCheck>(
         "readability-const-return-type");
+    CheckFactories.registerCheck<ContainerContainsCheck>(
+        "readability-container-contains");
     CheckFactories.registerCheck<ContainerDataPointerCheck>(
         "readability-container-data-pointer");
     CheckFactories.registerCheck<ContainerSizeEmptyCheck>(