[clang] [APINotes] Upstream Sema logic to apply API Notes to decls (PR #78445)

[Saleem Abdulrasool via cfe-commits]

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@@ -0,0 +1,989 @@
+//===--- SemaAPINotes.cpp - API Notes Handling ----------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file implements the mapping from API notes to declaration attributes.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/APINotes/APINotesReader.h"
+#include "clang/AST/Decl.h"
+#include "clang/AST/DeclObjC.h"
+#include "clang/Basic/SourceLocation.h"
+#include "clang/Lex/Lexer.h"
+#include "clang/Sema/SemaInternal.h"
+
+using namespace clang;
+
+namespace {
+enum class IsActive_t : bool { Inactive, Active };
+enum class IsReplacement_t : bool { Original, Replacement };
+
+struct VersionedInfoMetadata {
+  /// An empty version refers to unversioned metadata.
+  VersionTuple Version;
+  unsigned IsActive : 1;
+  unsigned IsReplacement : 1;
+
+  VersionedInfoMetadata(VersionTuple Version, IsActive_t Active,
+                        IsReplacement_t Replacement)
+      : Version(Version), IsActive(Active == IsActive_t::Active),
+        IsReplacement(Replacement == IsReplacement_t::Replacement) {}
+};
+} // end anonymous namespace
+
+/// Determine whether this is a multi-level pointer type.
+static bool isIndirectPointerType(QualType Type) {
+  QualType Pointee = Type->getPointeeType();
+  if (Pointee.isNull())
+    return false;
+
+  return Pointee->isAnyPointerType() || Pointee->isObjCObjectPointerType() ||
+         Pointee->isMemberPointerType();
+}
+
+/// Apply nullability to the given declaration.
+static void applyNullability(Sema &S, Decl *D, NullabilityKind Nullability,
+                             VersionedInfoMetadata Metadata) {
+  if (!Metadata.IsActive)
+    return;
+
+  auto IsUnmodified = [&](Decl *D, QualType QT,
+                          NullabilityKind Nullability) -> bool {
+    QualType Original = QT;
+    S.CheckImplicitNullabilityTypeSpecifier(QT, Nullability, D->getLocation(),
+                                            isa<ParmVarDecl>(D),
+                                            /*OverrideExisting=*/true);
+    return QT.getTypePtr() == Original.getTypePtr();
+  };
+
+  if (auto Function = dyn_cast<FunctionDecl>(D)) {
+    if (!IsUnmodified(D, Function->getReturnType(), Nullability)) {
+      QualType FnType = Function->getType();
+      Function->setType(FnType);
+    }
+  } else if (auto Method = dyn_cast<ObjCMethodDecl>(D)) {
+    QualType Type = Method->getReturnType();
+    if (!IsUnmodified(D, Type, Nullability)) {
+      Method->setReturnType(Type);
+
+      // Make it a context-sensitive keyword if we can.
+      if (!isIndirectPointerType(Type))
+        Method->setObjCDeclQualifier(Decl::ObjCDeclQualifier(
+            Method->getObjCDeclQualifier() | Decl::OBJC_TQ_CSNullability));
+    }
+  } else if (auto Value = dyn_cast<ValueDecl>(D)) {
+    QualType Type = Value->getType();
+    if (!IsUnmodified(D, Type, Nullability)) {
+      Value->setType(Type);
+
+      // Make it a context-sensitive keyword if we can.
+      if (auto Parm = dyn_cast<ParmVarDecl>(D)) {
+        if (Parm->isObjCMethodParameter() && !isIndirectPointerType(Type))
+          Parm->setObjCDeclQualifier(Decl::ObjCDeclQualifier(
+              Parm->getObjCDeclQualifier() | Decl::OBJC_TQ_CSNullability));
+      }
+    }
+  } else if (auto Property = dyn_cast<ObjCPropertyDecl>(D)) {
+    QualType Type = Property->getType();
+    if (!IsUnmodified(D, Type, Nullability)) {
+      Property->setType(Type, Property->getTypeSourceInfo());
+
+      // Make it a property attribute if we can.
+      if (!isIndirectPointerType(Type))
+        Property->setPropertyAttributes(
+            ObjCPropertyAttribute::kind_null_resettable);
+    }
+  }
+}
+
+/// Copy a string into ASTContext-allocated memory.
+static StringRef ASTAllocateString(ASTContext &Ctx, StringRef String) {
+  void *mem = Ctx.Allocate(String.size(), alignof(char *));
+  memcpy(mem, String.data(), String.size());
+  return StringRef(static_cast<char *>(mem), String.size());
+}
+
+static AttributeCommonInfo getPlaceholderAttrInfo() {
+  return AttributeCommonInfo(SourceRange(),
+                             AttributeCommonInfo::UnknownAttribute,
+                             {AttributeCommonInfo::AS_GNU,
+                              /*Spelling*/ 0, /*IsAlignas*/ false,
+                              /*IsRegularKeywordAttribute*/ false});
+}
+
+namespace {
+template <typename A> struct AttrKindFor {};
+
+#define ATTR(X)                                                                \
+  template <> struct AttrKindFor<X##Attr> {                                    \
+    static const attr::Kind value = attr::X;                                   \
+  };
+#include "clang/Basic/AttrList.inc"
+
+/// Handle an attribute introduced by API notes.
+///
+/// \param IsAddition Whether we should add a new attribute
+/// (otherwise, we might remove an existing attribute).
+/// \param CreateAttr Create the new attribute to be added.
+template <typename A>
+void handleAPINotedAttribute(
+    Sema &S, Decl *D, bool IsAddition, VersionedInfoMetadata Metadata,
+    llvm::function_ref<A *()> CreateAttr,
+    llvm::function_ref<Decl::attr_iterator(const Decl *)> GetExistingAttr) {
+  if (Metadata.IsActive) {
+    auto Existing = GetExistingAttr(D);
+    if (Existing != D->attr_end()) {
+      // Remove the existing attribute, and treat it as a superseded
+      // non-versioned attribute.
+      auto *Versioned = SwiftVersionedAdditionAttr::CreateImplicit(
+          S.Context, Metadata.Version, *Existing, /*IsReplacedByActive*/ true);
+
+      D->getAttrs().erase(Existing);
+      D->addAttr(Versioned);
+    }
+
+    // If we're supposed to add a new attribute, do so.
+    if (IsAddition) {
+      if (auto Attr = CreateAttr())
+        D->addAttr(Attr);
+    }
+
+  } else {
----------------
compnerd wrote:

I'm a bit torn. I don't know if it helps too much, but you can possibly end the `if (Metadata.IsActive)` clause with `return` to avoid the `else` and undent the rest of the code.

https://github.com/llvm/llvm-project/pull/78445