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

This patch extends readability-container-size-empty check allowing it to produce
warnings not only for STL containers, but also for containers, which provide two
functions matching following signatures:

* `size_type size() const;`
* `bool empty() const;`

Where `size_type` can be any kind of integer type.

This functionality was proposed in https://llvm.org/bugs/show_bug.cgi?id=26823
by Eugene Zelenko.

Approval: alexfh

Reviewers: alexfh, aaron.ballman, Eugene.Zelenko

Subscribers: etienneb, Prazek, hokein, xazax.hun, cfe-commits

Differential Revision: https://reviews.llvm.org/D24349

llvm-svn: 281307

clang-tools-extra/clang-tidy/readability/ContainerSizeEmptyCheck.cpp

@@ -7,11 +7,11 @@
 //
 //===----------------------------------------------------------------------===//
 #include "ContainerSizeEmptyCheck.h"
+#include "../utils/Matchers.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/ASTMatchers/ASTMatchers.h"
 #include "clang/Lex/Lexer.h"
 #include "llvm/ADT/StringRef.h"
-#include "../utils/Matchers.h"
 
 using namespace clang::ast_matchers;
 
@@ -29,11 +29,16 @@ void ContainerSizeEmptyCheck::registerMatchers(MatchFinder *Finder) {
   if (!getLangOpts().CPlusPlus)
     return;
 
-  const auto stlContainer = hasAnyName(
+  const auto validContainer = cxxRecordDecl(isSameOrDerivedFrom(
-      "array", "basic_string", "deque", "forward_list", "list", "map",
+      namedDecl(
-      "multimap", "multiset", "priority_queue", "queue", "set", "stack",
+          has(cxxMethodDecl(
-      "unordered_map", "unordered_multimap", "unordered_multiset",
+                  isConst(), parameterCountIs(0), isPublic(), hasName("size"),
-      "unordered_set", "vector");
+                  returns(qualType(isInteger(), unless(booleanType()))))
+                  .bind("size")),
+          has(cxxMethodDecl(isConst(), parameterCountIs(0), isPublic(),
+                            hasName("empty"), returns(booleanType()))
+                  .bind("empty")))
+          .bind("container")));
 
   const auto WrongUse = anyOf(
       hasParent(binaryOperator(
@@ -49,12 +54,11 @@ void ContainerSizeEmptyCheck::registerMatchers(MatchFinder *Finder) {
       hasParent(explicitCastExpr(hasDestinationType(booleanType()))));
 
   Finder->addMatcher(
-      cxxMemberCallExpr(
+      cxxMemberCallExpr(on(expr(anyOf(hasType(validContainer),
-          on(expr(anyOf(hasType(namedDecl(stlContainer)),
+                                      hasType(pointsTo(validContainer)),
-                        hasType(pointsTo(namedDecl(stlContainer))),
+                                      hasType(references(validContainer))))
-                        hasType(references(namedDecl(stlContainer)))))
+                               .bind("STLObject")),
-                 .bind("STLObject")),
+                        callee(cxxMethodDecl(hasName("size"))), WrongUse)
-          callee(cxxMethodDecl(hasName("size"))), WrongUse)
           .bind("SizeCallExpr"),
       this);
 }
@@ -142,9 +146,17 @@ void ContainerSizeEmptyCheck::check(const MatchFinder::MatchResult &Result) {
       Hint = FixItHint::CreateReplacement(MemberCall->getSourceRange(),
                                           "!" + ReplacementText);
   }
+
   diag(MemberCall->getLocStart(), "the 'empty' method should be used to check "
                                   "for emptiness instead of 'size'")
       << Hint;
+
+  const auto *Container = Result.Nodes.getNodeAs<NamedDecl>("container");
+  const auto *Empty = Result.Nodes.getNodeAs<FunctionDecl>("empty");
+
+  diag(Empty->getLocation(), "method %0::empty() defined here",
+       DiagnosticIDs::Note)
+      << Container;
 }
 
 } // namespace readability

clang-tools-extra/docs/clang-tidy/checks/readability-container-size-empty.rst

@@ -11,6 +11,16 @@ The emptiness of a container should be checked using the ``empty()`` method
 instead of the ``size()`` method. It is not guaranteed that ``size()`` is a
 constant-time function, and it is generally more efficient and also shows
 clearer intent to use ``empty()``. Furthermore some containers may implement
-the ``empty()`` method but not implement the ``size()`` method. Using ``empty()``
+the ``empty()`` method but not implement the ``size()`` method. Using
-whenever possible makes it easier to switch to another container in the
+``empty()`` whenever possible makes it easier to switch to another container in
-future.
+the future.
+
+The check issues warning if a container has ``size()`` and ``empty()`` methods
+matching following signatures:
+
+code-block:: c++
+
+  size_type size() const;
+  bool empty() const;
+
+`size_type` can be any kind of integer type.

clang-tools-extra/test/clang-tidy/readability-container-size-empty.cpp

@@ -24,9 +24,43 @@ template <typename T> struct set {
 };
 }
 
-
 }
 
+template <typename T>
+class TemplatedContainer {
+public:
+  int size() const;
+  bool empty() const;
+};
+
+template <typename T>
+class PrivateEmpty {
+public:
+  int size() const;
+private:
+  bool empty() const;
+};
+
+struct BoolSize {
+  bool size() const;
+  bool empty() const;
+};
+
+struct EnumSize {
+  enum E { one };
+  enum E size() const;
+  bool empty() const;
+};
+
+class Container {
+public:
+  int size() const;
+  bool empty() const;
+};
+
+class Derived : public Container {
+};
+
 int main() {
   std::set<int> intSet;
   std::string str;
@@ -39,6 +73,7 @@ int main() {
     ;
   // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used to check for emptiness instead of 'size' [readability-container-size-empty]
   // CHECK-FIXES: {{^  }}if (intSet.empty()){{$}}
+  // CHECK-MESSAGES: :23:8: note: method 'set<int>'::empty() defined here
   if (str.size() == 0)
     ;
   // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used
@@ -127,6 +162,116 @@ int main() {
     ;
   // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used
   // CHECK-FIXES: {{^  }}if (vect4.empty()){{$}}
+
+  TemplatedContainer<void> templated_container;
+  if (templated_container.size() == 0)
+    ;
+  // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used
+  // CHECK-FIXES: {{^  }}if (templated_container.empty()){{$}}
+  if (templated_container.size() != 0)
+    ;
+  // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used
+  // CHECK-FIXES: {{^  }}if (!templated_container.empty()){{$}}
+  if (0 == templated_container.size())
+    ;
+  // CHECK-MESSAGES: :[[@LINE-2]]:12: warning: the 'empty' method should be used
+  // CHECK-FIXES: {{^  }}if (templated_container.empty()){{$}}
+  if (0 != templated_container.size())
+    ;
+  // CHECK-MESSAGES: :[[@LINE-2]]:12: warning: the 'empty' method should be used
+  // CHECK-FIXES: {{^  }}if (!templated_container.empty()){{$}}
+  if (templated_container.size() > 0)
+    ;
+  // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used
+  // CHECK-FIXES: {{^  }}if (!templated_container.empty()){{$}}
+  if (0 < templated_container.size())
+    ;
+  // CHECK-MESSAGES: :[[@LINE-2]]:11: warning: the 'empty' method should be used
+  // CHECK-FIXES: {{^  }}if (!templated_container.empty()){{$}}
+  if (templated_container.size() < 1)
+    ;
+  // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used
+  // CHECK-FIXES: {{^  }}if (templated_container.empty()){{$}}
+  if (1 > templated_container.size())
+    ;
+  // CHECK-MESSAGES: :[[@LINE-2]]:11: warning: the 'empty' method should be used
+  // CHECK-FIXES: {{^  }}if (templated_container.empty()){{$}}
+  if (templated_container.size() >= 1)
+    ;
+  // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used
+  // CHECK-FIXES: {{^  }}if (!templated_container.empty()){{$}}
+  if (1 <= templated_container.size())
+    ;
+  // CHECK-MESSAGES: :[[@LINE-2]]:12: warning: the 'empty' method should be used
+  // CHECK-FIXES: {{^  }}if (!templated_container.empty()){{$}}
+  if (templated_container.size() > 1) // no warning
+    ;
+  if (1 < templated_container.size()) // no warning
+    ;
+  if (templated_container.size() <= 1) // no warning
+    ;
+  if (1 >= templated_container.size()) // no warning
+    ;
+  if (!templated_container.size())
+    ;
+  // CHECK-MESSAGES: :[[@LINE-2]]:8: warning: the 'empty' method should be used
+  // CHECK-FIXES: {{^  }}if (templated_container.empty()){{$}}
+  if (templated_container.size())
+    ;
+  // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used
+  // CHECK-FIXES: {{^  }}if (!templated_container.empty()){{$}}
+
+  if (templated_container.empty())
+    ;
+
+  // No warnings expected.
+  PrivateEmpty<void> private_empty;
+  if (private_empty.size() == 0)
+    ;
+  if (private_empty.size() != 0)
+    ;
+  if (0 == private_empty.size())
+    ;
+  if (0 != private_empty.size())
+    ;
+  if (private_empty.size() > 0)
+    ;
+  if (0 < private_empty.size())
+    ;
+  if (private_empty.size() < 1)
+    ;
+  if (1 > private_empty.size())
+    ;
+  if (private_empty.size() >= 1)
+    ;
+  if (1 <= private_empty.size())
+    ;
+  if (private_empty.size() > 1)
+    ;
+  if (1 < private_empty.size())
+    ;
+  if (private_empty.size() <= 1)
+    ;
+  if (1 >= private_empty.size())
+    ;
+  if (!private_empty.size())
+    ;
+  if (private_empty.size())
+    ;
+
+  // Types with weird size() return type.
+  BoolSize bs;
+  if (bs.size() == 0)
+    ;
+  EnumSize es;
+  if (es.size() == 0)
+    ;
+
+  Derived derived;
+  if (derived.size() == 0)
+    ;
+  // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used
+  // CHECK-FIXES: {{^  }}if (derived.empty()){{$}}
 }
 
 #define CHECKSIZE(x) if (x.size())
@@ -136,12 +281,22 @@ template <typename T> void f() {
   std::vector<T> v;
   if (v.size())
     ;
-  // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used
+  // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used to check for emptiness instead of 'size' [readability-container-size-empty]
   // CHECK-FIXES: {{^  }}if (!v.empty()){{$}}
   // CHECK-FIXES-NEXT: ;
   CHECKSIZE(v);
   // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: the 'empty' method should be used
   // CHECK-MESSAGES: CHECKSIZE(v);
+
+  TemplatedContainer<T> templated_container;
+  if (templated_container.size())
+    ;
+  // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used
+  // CHECK-FIXES: {{^  }}if (!templated_container.empty()){{$}}
+  // CHECK-FIXES-NEXT: ;
+  CHECKSIZE(templated_container);
+  // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: the 'empty' method should be used
+  // CHECK-MESSAGES: CHECKSIZE(templated_container);
 }
 
 void g() {