[clang][lex] Remove `Preprocessor::GetCurDirLookup()`

[jansvoboda11]

Summary

Preprocessor exposes the search directory iterator via GetCurDirLookup() getter, which is only used in two static functions.

To simplify reasoning about search directory iterators/references and to simplify the Preprocessor API, this patch makes the two static functions private member functions and removes the getter entirely.

Depends D119708.

[dexonsmith]

LGTM too.

clang/include/clang/Lex/Preprocessor.h

public:
   Optional<FileEntryRef>
   LookupFile(SourceLocation FilenameLoc, StringRef Filename, bool isAngled,
              const DirectoryLookup *FromDir, const FileEntry *FromFile,
              const DirectoryLookup **CurDir, SmallVectorImpl<char> *SearchPath,
              SmallVectorImpl<char> *RelativePath,
              ModuleMap::KnownHeader *SuggestedModule, bool *IsMapped,
              bool *IsFrameworkFound, bool SkipCache = false);
 
-  /// Get the DirectoryLookup structure used to find the current
-  /// FileEntry, if CurLexer is non-null and if applicable.
-  ///
-  /// This allows us to implement \#include_next and find directory-specific
-  /// properties.
-  const DirectoryLookup *GetCurDirLookup() { return CurDirLookup; }
-
   /// Return true if we're in the top-level file, not in a \#include.
   bool isInPrimaryFile() const;
 
   /// Lex an on-off-switch (C99 6.10.6p2) and verify that it is
   /// followed by EOD.  Return true if the token is not a valid on-off-switch.
   bool LexOnOffSwitch(tok::OnOffSwitch &Result);
 
   bool CheckMacroName(Token &MacroNameTok, MacroUse isDefineUndef,
private:
   };
 
   /// Evaluate an integer constant expression that may occur after a
   /// \#if or \#elif directive and return a \p DirectiveEvalResult object.
   ///
   /// If the expression is equivalent to "!defined(X)" return X in IfNDefMacro.
   DirectiveEvalResult EvaluateDirectiveExpression(IdentifierInfo *&IfNDefMacro);
 
+  /// Process a '__has_include("path")' expression.
+  ///
+  /// Returns true if successful.
+  bool EvaluateHasInclude(Token &Tok, IdentifierInfo *II);
+
+  /// Process '__has_include_next("path")' expression.
+  ///
+  /// Returns true if successful.
+  bool EvaluateHasIncludeNext(Token &Tok, IdentifierInfo *II);
+
   /// Install the standard preprocessor pragmas:
   /// \#pragma GCC poison/system_header/dependency and \#pragma once.
   void RegisterBuiltinPragmas();
 
   /// Register builtin macros such as __LINE__ with the identifier table.
   void RegisterBuiltinMacros();
 
   /// If an identifier token is read that is to be expanded as a macro, handle

clang/lib/Lex/PPMacroExpansion.cpp

if (File)
           PP.getHeaderSearchInfo().getFileDirFlavor(&File->getFileEntry());
     Callbacks->HasInclude(FilenameLoc, Filename, isAngled, File, FileType);
   }
 
   // Get the result value.  A result of true means the file exists.
   return File.hasValue();
 }
 
-/// EvaluateHasInclude - Process a '__has_include("path")' expression.
-/// Returns true if successful.
-static bool EvaluateHasInclude(Token &Tok, IdentifierInfo *II,
-                               Preprocessor &PP) {
-  return EvaluateHasIncludeCommon(Tok, II, PP, nullptr, nullptr);
+bool Preprocessor::EvaluateHasInclude(Token &Tok, IdentifierInfo *II) {
+  return EvaluateHasIncludeCommon(Tok, II, *this, nullptr, nullptr);
 }
 
-/// EvaluateHasIncludeNext - Process '__has_include_next("path")' expression.
-/// Returns true if successful.
-static bool EvaluateHasIncludeNext(Token &Tok,
-                                   IdentifierInfo *II, Preprocessor &PP) {
+bool Preprocessor::EvaluateHasIncludeNext(Token &Tok, IdentifierInfo *II) {
   // __has_include_next is like __has_include, except that we start
   // searching after the current found directory.  If we can't do this,
   // issue a diagnostic.
   // FIXME: Factor out duplication with
   // Preprocessor::HandleIncludeNextDirective.
-  const DirectoryLookup *Lookup = PP.GetCurDirLookup();
+  const DirectoryLookup *Lookup = CurDirLookup;
   const FileEntry *LookupFromFile = nullptr;
-  if (PP.isInPrimaryFile() && PP.getLangOpts().IsHeaderFile) {
+  if (isInPrimaryFile() && getLangOpts().IsHeaderFile) {
     // If the main file is a header, then it's either for PCH/AST generation,
     // or libclang opened it. Either way, handle it as a normal include below
     // and do not complain about __has_include_next.
-  } else if (PP.isInPrimaryFile()) {
+  } else if (isInPrimaryFile()) {
     Lookup = nullptr;
-    PP.Diag(Tok, diag::pp_include_next_in_primary);
-  } else if (PP.getCurrentLexerSubmodule()) {
+    Diag(Tok, diag::pp_include_next_in_primary);
+  } else if (getCurrentLexerSubmodule()) {
     // Start looking up in the directory *after* the one in which the current
     // file would be found, if any.
-    assert(PP.getCurrentLexer() && "#include_next directive in macro?");
-    LookupFromFile = PP.getCurrentLexer()->getFileEntry();
+    assert(getCurrentLexer() && "#include_next directive in macro?");
+    LookupFromFile = getCurrentLexer()->getFileEntry();
     Lookup = nullptr;
   } else if (!Lookup) {
-    PP.Diag(Tok, diag::pp_include_next_absolute_path);
+    Diag(Tok, diag::pp_include_next_absolute_path);
   } else {
     // Start looking up in the next directory.
     ++Lookup;
   }
 
-  return EvaluateHasIncludeCommon(Tok, II, PP, Lookup, LookupFromFile);
+  return EvaluateHasIncludeCommon(Tok, II, *this, Lookup, LookupFromFile);
 }
 
 /// Process single-argument builtin feature-like macros that return
 /// integer values.
 static void EvaluateFeatureLikeBuiltinMacro(llvm::raw_svector_ostream& OS,
                                             Token &Tok, IdentifierInfo *II,
                                             Preprocessor &PP, bool ExpandArgs,
                                             llvm::function_ref<
EvaluateFeatureLikeBuiltinMacro(OS, Tok, II, *this, true,
         });
   } else if (II == Ident__has_include ||
              II == Ident__has_include_next) {
     // The argument to these two builtins should be a parenthesized
     // file name string literal using angle brackets (<>) or
     // double-quotes ("").
     bool Value;
     if (II == Ident__has_include)
-      Value = EvaluateHasInclude(Tok, II, *this);
+      Value = EvaluateHasInclude(Tok, II);
     else
-      Value = EvaluateHasIncludeNext(Tok, II, *this);
+      Value = EvaluateHasIncludeNext(Tok, II);
 
     if (Tok.isNot(tok::r_paren))
       return;
     OS << (int)Value;
     Tok.setKind(tok::numeric_constant);
   } else if (II == Ident__has_warning) {
     // The argument should be a parenthesized string literal.
     EvaluateFeatureLikeBuiltinMacro(OS, Tok, II, *this, false,