[clang-tidy] Fix a regression of readability-container-size-empty after the AST ElaboratedType change.

With 15f3cd6, we no longer emit a
diagnostic on a real std::vector case where the size method returns a
sugar `size_type`. This patch fixes it.

```
std::vector<int> v;
if (v.size() == 0) // => no check diagnostics
  ;
```

Differential Revision: https://reviews.llvm.org/D131390

Author: hokein

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

@@ -86,6 +86,9 @@ AST_MATCHER(Expr, usedInBooleanContext) {
 AST_MATCHER(CXXConstructExpr, isDefaultConstruction) {
   return Node.getConstructor()->isDefaultConstructor();
 }
+AST_MATCHER(QualType, isIntegralType) {
+  return Node->isIntegralType(Finder->getASTContext());
+}
 } // namespace ast_matchers
 namespace tidy {
 namespace readability {
@@ -99,10 +102,9 @@ ContainerSizeEmptyCheck::ContainerSizeEmptyCheck(StringRef Name,
 void ContainerSizeEmptyCheck::registerMatchers(MatchFinder *Finder) {
   const auto ValidContainerRecord = cxxRecordDecl(isSameOrDerivedFrom(
       namedDecl(
-          has(cxxMethodDecl(isConst(), parameterCountIs(0), isPublic(),
-                            hasName("size"),
-                            returns(qualType(isInteger(), unless(booleanType()),
-                                             unless(elaboratedType()))))
+          has(cxxMethodDecl(
+                  isConst(), parameterCountIs(0), isPublic(), hasName("size"),
+                  returns(qualType(isIntegralType(), unless(booleanType()))))
                   .bind("size")),
           has(cxxMethodDecl(isConst(), parameterCountIs(0), isPublic(),
                             hasName("empty"), returns(booleanType()))

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

@@ -718,3 +718,16 @@ bool call_through_unique_ptr_deref(const std::unique_ptr<std::vector<int>> &ptr)
   // CHECK-MESSAGES: :9:8: note: method 'vector'::empty() defined here
   // CHECK-FIXES: {{^  }}return !(*ptr).empty();
 }
+
+struct TypedefSize {
+  typedef int size_type;
+  size_type size() const;
+  bool empty() const;
+};
+void test() {
+  TypedefSize ts;
+  if (ts.size() == 0)
+    ;
+  // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used
+  // CHECK-FIXES: {{^  }}if (ts.empty()){{$}}
+}