From fbce89e4c17fe4486beba5fad91822cfd551e8e9 Mon Sep 17 00:00:00 2001
From: Javier Alvarez Garcia <ja@daedalean.ai>
Date: Tue, 2 Aug 2022 09:12:32 +0200
Subject: [PATCH] Fixes for type-conversions

---
 .../daedalean/TypeConversionsCheck.cpp         | 18 ++++++++++++++++--
 .../checkers/daedalean-type-conversions.cpp    |  2 ++
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/clang-tools-extra/clang-tidy/daedalean/TypeConversionsCheck.cpp b/clang-tools-extra/clang-tidy/daedalean/TypeConversionsCheck.cpp
index 6e531f8c6a0674..6206e15536e90b 100644
--- a/clang-tools-extra/clang-tidy/daedalean/TypeConversionsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/daedalean/TypeConversionsCheck.cpp
@@ -27,6 +27,7 @@ QualType getPointee(QualType type) {
     return llvm::cast<BlockPointerType>(type)->getPointeeType();
   }
   assert(false && "Not a valid pointer type!");
+  return type;
 }
 
 bool hasPointerRepresentation(QualType type) {
@@ -216,7 +217,8 @@ void TypeConversionsCheck::handleImplicitCast(clang::ASTContext *context,
     return;
   }
 
-  if (sourceType->isNullPtrType() && destType->isPointerType()) {
+  if (sourceType->isNullPtrType() &&
+      (destType->isPointerType() || destType->isMemberPointerType())) {
     // Casting from nullptr to a pointer type is always allowed
     return;
   }
@@ -226,7 +228,7 @@ void TypeConversionsCheck::handleImplicitCast(clang::ASTContext *context,
     return;
   }
 
-  if (sourceType->isBuiltinType()) {
+  if (llvm::isa<BuiltinType>(sourceType)) {
     const BuiltinType *Builtin = llvm::dyn_cast<BuiltinType>(sourceType);
     if ((Builtin->getKind() == BuiltinType::Kind::BuiltinFn) &&
         destType->isFunctionPointerType()) {
@@ -265,6 +267,18 @@ void TypeConversionsCheck::handleImplicitCast(clang::ASTContext *context,
     return;
   }
 
+  if (hasPointerRepresentation(sourceType) &&
+      hasPointerRepresentation(destType)) {
+    const CXXRecordDecl *sourceRecord =
+        getPointee(sourceType)->getAsCXXRecordDecl();
+    const CXXRecordDecl *destRecord =
+        getPointee(destType)->getAsCXXRecordDecl();
+    if (sourceRecord && destRecord && sourceRecord->isDerivedFrom(destRecord)) {
+      // Cast pointer or reference from child to base MAY be implicit.
+      return;
+    }
+  }
+
   diag(location, "Type conversions MUST be explicit");
   diag(location, "Implicit conversion from %1 to %0", DiagnosticIDs::Note)
       << destType << sourceType;
diff --git a/clang-tools-extra/test/clang-tidy/checkers/daedalean-type-conversions.cpp b/clang-tools-extra/test/clang-tidy/checkers/daedalean-type-conversions.cpp
index 36e5e9ff00bcda..85f2a899dc9e5f 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/daedalean-type-conversions.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/daedalean-type-conversions.cpp
@@ -73,7 +73,9 @@ void testImplicitCastFromDerivedPtrToBase() {
 
   // Implicit B to A is fine
   A &NonConstA{Obj};
+  A *NonConstAPtr{&Obj};
   static_cast<void>(NonConstA);
+  static_cast<void>(NonConstAPtr);
 }
 
 void testImplicitCastAddingQualifiers() {