[clang-tools-extra] create new clang-tidy check to add namespaces to symbol references (PR #70621)

[Piotr Zegar via cfe-commits]

================
@@ -0,0 +1,220 @@
+// RUN: %check_clang_tidy %s readability-use-explicit-namespaces %t
+
+namespace foo {
+void doSomething() {}
+
+template <class T> void doTemplateThing(T &value) { value = value * 2; }
+
+struct StructTest {
+  int StructIntMember;
+};
+
+class ClassTest {
+public:
+  int ClassIntMember;
+  typedef int ClassTypeDefMember;
+};
+
+enum EnumTest {
+  EnumValueOne,
+  EnumValueTwo,
+  EnumValueThree,
+};
+
+template <class T> class TemplateClassTest {
+public:
+  T TemplatizedData;
+};
+
+typedef int TypeDefTest;
+typedef void (*event_callback)(ClassTest &value);
+
+} // namespace foo
+
+class OutsideNamespace : public foo::ClassTest {
+public:
+  ClassTypeDefMember UseTypeFromParentOk;
+};
+
+OutsideNamespace::ClassTypeDefMember UseTypeFromClassInheritedFromParentOk;
+
+foo::ClassTest AlreadyQualifiedOk() {
+  foo::doSomething();
+  foo::StructTest first;
+  foo::ClassTest second;
+  second.ClassIntMember = 55;
+  foo::EnumTest picked = foo::EnumValueThree;
+  foo::TemplateClassTest<foo::ClassTest> data;
+  foo::TemplateClassTest<
+      foo::TemplateClassTest<foo::TemplateClassTest<foo::ClassTest>>>
+      dataNested;
+  foo::StructTest many[8];
+  foo::TypeDefTest integer = 22;
+  foo::doTemplateThing(integer);
+  foo::doTemplateThing<foo::TypeDefTest>(integer);
+  struct foo::StructTest fooStruct;
+  auto lambdaReturn = []() -> foo::ClassTest { return foo::ClassTest(); };
+  auto lambdaTypes = [](foo::StructTest &start,
+                        foo::StructTest *end) -> foo::ClassTest {
+    return foo::ClassTest();
+  };
+
+  foo::ClassTest ConstructOnStack;
+  new foo::ClassTest;
+  foo::TemplateClassTest<foo::ClassTest> ConstructTemplateOnStack;
+  new foo::TemplateClassTest<foo::ClassTest>;
+  foo::ClassTest();
+  new foo::ClassTest();
+  foo::TemplateClassTest<foo::ClassTest>();
+  new foo::TemplateClassTest<foo::ClassTest>();
+  return foo::ClassTest();
+}
+
+namespace foo {
+ClassTest InsideNamespaceFooOk() {
+  doSomething();
+  StructTest first;
+  ClassTest second;
+  second.ClassIntMember = 55;
+  EnumTest picked = EnumValueThree;
+  TemplateClassTest<ClassTest> data;
+  TemplateClassTest<TemplateClassTest<TemplateClassTest<ClassTest>>> dataNested;
+  StructTest many[8];
+  TypeDefTest integer = 22;
+  doTemplateThing(integer);
+  doTemplateThing<TypeDefTest>(integer);
+  struct StructTest fooStruct;
+  auto lambdaReturn = []() -> ClassTest { return ClassTest(); };
+  auto lambdaTypes = [](StructTest &start, StructTest *end) -> ClassTest {
+    return ClassTest();
+  };
+
+  ClassTest ConstructOnStack;
+  new ClassTest;
+  TemplateClassTest<ClassTest> ConstructTemplateOnStack;
+  new TemplateClassTest<ClassTest>;
+  ClassTest();
+  new ClassTest();
+  TemplateClassTest<ClassTest>();
+  new TemplateClassTest<ClassTest>();
+  return ClassTest();
+}
+} // namespace foo
+
+using namespace foo;
+
+ClassTest FixAllMissingFoo()
+// CHECK-MESSAGES: :[[@LINE-1]]:1: warning: Missing namespace qualifiers
+// CHECK-FIXES:  foo::
+{
+  doSomething();
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: Missing namespace qualifiers foo::
+  // CHECK-FIXES:  foo::
+  StructTest first;
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: Missing namespace qualifiers foo::
+  // CHECK-FIXES:  foo::
+  ClassTest second;
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: Missing namespace qualifiers foo::
+  // CHECK-FIXES:  foo::
+  second.ClassIntMember = 55;
+  EnumTest picked = EnumValueThree;
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: Missing namespace qualifiers foo::
----------------
PiotrZSL wrote:

warnings should start with lower caps.

https://github.com/llvm/llvm-project/pull/70621