From cb4ae697f79c6d4ef126e51fcd7168462160847c Mon Sep 17 00:00:00 2001
From: outfoxxed <outfoxxed@outfoxxed.me>
Date: Fri, 27 Oct 2023 03:10:01 -0700
Subject: [PATCH] feat: add tidyfox-explicit-thisptr

Enforces explicit usage of the thisptr unconditionally
---
 CMakeLists.txt           |  2 +-
 README.md                |  7 +++++--
 src/explicit_thisptr.cpp | 24 ++++++++++++++++++++++++
 src/explicit_thisptr.hpp | 15 +++++++++++++++
 src/lib.cpp              |  6 +++++-
 5 files changed, 50 insertions(+), 4 deletions(-)
 create mode 100644 src/explicit_thisptr.cpp
 create mode 100644 src/explicit_thisptr.hpp

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0ba271b..d9196e6 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,5 +1,5 @@
 cmake_minimum_required(VERSION 3.20)
-project(tidyfox VERSION "0.0.1")
+project(tidyfox VERSION "0.1.0")
 
 set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED YES)
diff --git a/README.md b/README.md
index 708f985..918607e 100644
--- a/README.md
+++ b/README.md
@@ -8,8 +8,11 @@ If you aren't running nix, use the provided Justfile.
 Run `just release` to make a release build. You must have llvm and clang 16 dev packages in $PATH. (`FindClang.cmake` must exist)
 
 # Usage
-Tidyfox lints are supplied under the `tidyfox-` namespace. Currently there are no lints.
-The plugin can be loaded via `clang-tidy -load=/path/to/libtidyfox.so`
+Tidyfox lints are supplied under the `tidyfox-` namespace.
+The plugin can be loaded via `clang-tidy -load=/path/to/libtidyfox.so`.
+
+## Lints
+`tidyfox-explicit-thisptr` - requires that `this->` is used unconditionally for class members.
 
 # Contributing
 There is a `shell.nix` file which will load all the necessary dependencies.
diff --git a/src/explicit_thisptr.cpp b/src/explicit_thisptr.cpp
new file mode 100644
index 0000000..5a28aa2
--- /dev/null
+++ b/src/explicit_thisptr.cpp
@@ -0,0 +1,24 @@
+#include "explicit_thisptr.hpp"
+
+#include <clang/ASTMatchers/ASTMatchFinder.h>
+#include <clang/ASTMatchers/ASTMatchers.h>
+
+namespace clang::tidy::tidyfox {
+using namespace ast_matchers;
+
+ExplicitThisptrCheck::ExplicitThisptrCheck(StringRef name, ClangTidyContext* context):
+    ClangTidyCheck(name, context) {}
+
+void ExplicitThisptrCheck::registerMatchers(MatchFinder* finder) {
+	finder->addMatcher(cxxThisExpr().bind("thisptr"), this);
+}
+
+void ExplicitThisptrCheck::check(const MatchFinder::MatchResult& result) {
+	const auto* matched = result.Nodes.getNodeAs<CXXThisExpr>("thisptr");
+	if (!matched->isImplicit()) return;
+
+	this->diag(matched->getLocation(), "class member accesses must explicitly use thisptr")
+	    << FixItHint::CreateInsertion(matched->getLocation(), "this->");
+}
+
+} // namespace clang::tidy::tidyfox
diff --git a/src/explicit_thisptr.hpp b/src/explicit_thisptr.hpp
new file mode 100644
index 0000000..3c90629
--- /dev/null
+++ b/src/explicit_thisptr.hpp
@@ -0,0 +1,15 @@
+#pragma once
+
+#include <clang-tidy/ClangTidyCheck.h>
+#include <clang/ASTMatchers/ASTMatchFinder.h>
+
+namespace clang::tidy::tidyfox {
+
+class ExplicitThisptrCheck: public ClangTidyCheck {
+public:
+	ExplicitThisptrCheck(StringRef name, ClangTidyContext* context);
+	void registerMatchers(ast_matchers::MatchFinder* finder) override;
+	void check(const ast_matchers::MatchFinder::MatchResult& result) override;
+};
+
+} // namespace clang::tidy::tidyfox
diff --git a/src/lib.cpp b/src/lib.cpp
index bba5432..0c884b2 100644
--- a/src/lib.cpp
+++ b/src/lib.cpp
@@ -3,11 +3,15 @@
 #include <clang-tidy/ClangTidyModule.h>
 #include <clang-tidy/ClangTidyModuleRegistry.h>
 
+#include "explicit_thisptr.hpp"
+
 namespace clang::tidy::tidyfox {
 
 class TidyfoxClangTidyModule: public ClangTidyModule {
 public:
-	void addCheckFactories([[maybe_unused]] ClangTidyCheckFactories& check_factories) override {}
+	void addCheckFactories(ClangTidyCheckFactories& check_factories) override {
+		check_factories.registerCheck<ExplicitThisptrCheck>("tidyfox-explicit-thisptr");
+	}
 };
 
 static const ClangTidyModuleRegistry::Add<TidyfoxClangTidyModule>