[clang-tidy] New check: bugprone-suspicious-include

Detects and fixes suspicious code like: `#include "foo.cpp"`.

Inspired by: https://twitter.com/lefticus/status/1228458240364687360?s=20

https://reviews.llvm.org/D74669

2 files changed, 23 insertions, 4 deletions

diff --git a/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.cpp b/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.cpp
index d6f4b2a..4eaf8bc 100644
--- a/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.cpp
+++ b/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.cpp
@@ -53,13 +53,20 @@ bool parseFileExtensions(StringRef AllFileExtensions,
   return true;
 }
 
-bool isFileExtension(StringRef FileName,
-                     const FileExtensionsSet &FileExtensions) {
+llvm::Optional<StringRef>
+getFileExtension(StringRef FileName, const FileExtensionsSet &FileExtensions) {
   StringRef Extension = llvm::sys::path::extension(FileName);
   if (Extension.empty())
-    return false;
+    return llvm::None;
   // Skip "." prefix.
-  return FileExtensions.count(Extension.substr(1)) > 0;
+  if (!FileExtensions.count(Extension.substr(1)))
+    return llvm::None;
+  return Extension;
+}
+
+bool isFileExtension(StringRef FileName,
+                     const FileExtensionsSet &FileExtensions) {
+  return getFileExtension(FileName, FileExtensions).hasValue();
 }
 
 } // namespace utils
diff --git a/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.h b/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.h
index 43fc573..e5dfae1 100644
--- a/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.h
+++ b/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.h
@@ -11,6 +11,7 @@
 
 #include "clang/Basic/SourceLocation.h"
 #include "clang/Basic/SourceManager.h"
+#include "llvm/ADT/Optional.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/StringRef.h"
 
@@ -36,6 +37,12 @@ bool isSpellingLocInHeaderFile(SourceLocation Loc, SourceManager &SM,
 /// extensions.
 inline StringRef defaultHeaderFileExtensions() { return ";h;hh;hpp;hxx"; }
 
+/// Returns recommended default value for the list of implementaiton file
+/// extensions.
+inline StringRef defaultImplementationFileExtensions() {
+  return "c;cc;cpp;cxx";
+}
+
 /// Returns recommended default value for the list of file extension
 /// delimiters.
 inline StringRef defaultFileExtensionDelimiters() { return ",;"; }
@@ -45,6 +52,11 @@ bool parseFileExtensions(StringRef AllFileExtensions,
                          FileExtensionsSet &FileExtensions,
                          StringRef Delimiters);
 
+/// Decides whether a file has a header file extension.
+/// Returns the file extension, if included in the provided set.
+llvm::Optional<StringRef>
+getFileExtension(StringRef FileName, const FileExtensionsSet &FileExtensions);
+
 /// Decides whether a file has one of the specified file extensions.
 bool isFileExtension(StringRef FileName,
                      const FileExtensionsSet &FileExtensions);