Make SourceManager::createFileID(UnownedTag, ...) take a const llvm::MemoryBuffer*

[thakis]

Summary

Requires making the llvm::MemoryBuffer* stored by SourceManager const, which in turn requires making the accessors for that return const llvm::MemoryBuffer*s and updating all call sites.

The original motivation for this was to use it and fix the TODO in CodeGenAction.cpp's ConvertBackendLocation() by using the UnownedTag version of createFileID, and since llvm::SourceMgr* hands out a const llvm::MemoryBuffer* this is required. I'm not sure if fixing the TODO this way actually works, but this seems like a good change on its own anyways.

No intended behavior change.

[rnk]

lgtm!

clang-tidy/bugprone/SuspiciousSemicolonCheck.cpp

void SuspiciousSemicolonCheck::check(const MatchFinder::MatchResult &Result) {
   const bool IsIfStmt = isa<IfStmt>(Statement);
 
   if (!IsIfStmt &&
       SM.getSpellingLineNumber(Token.getLocation()) != SemicolonLine)
     return;
 
   SourceLocation LocEnd = Semicolon->getEndLoc();
   FileID FID = SM.getFileID(LocEnd);
-  llvm::MemoryBuffer *Buffer = SM.getBuffer(FID, LocEnd);
+  const llvm::MemoryBuffer *Buffer = SM.getBuffer(FID, LocEnd);
   Lexer Lexer(SM.getLocForStartOfFile(FID), Ctxt.getLangOpts(),
               Buffer->getBufferStart(), SM.getCharacterData(LocEnd) + 1,
               Buffer->getBufferEnd());
   if (Lexer.LexFromRawLexer(Token))
     return;
 
   unsigned BaseIndent = SM.getSpellingColumnNumber(Statement->getBeginLoc());
   unsigned NewTokenIndent = SM.getSpellingColumnNumber(Token.getLocation());

clang-tidy/misc/StaticAssertCheck.cpp

diag(AssertLoc, "found assert() that could be replaced by static_assert()")
       << FixItHints;
 }
 
 SourceLocation StaticAssertCheck::getLastParenLoc(const ASTContext *ASTCtx,
                                                   SourceLocation AssertLoc) {
   const LangOptions &Opts = ASTCtx->getLangOpts();
   const SourceManager &SM = ASTCtx->getSourceManager();
 
-  llvm::MemoryBuffer *Buffer = SM.getBuffer(SM.getFileID(AssertLoc));
+  const llvm::MemoryBuffer *Buffer = SM.getBuffer(SM.getFileID(AssertLoc));
   if (!Buffer)
     return SourceLocation();
 
   const char *BufferPos = SM.getCharacterData(AssertLoc);
 
   Token Token;
   Lexer Lexer(SM.getLocForStartOfFile(SM.getFileID(AssertLoc)), Opts,
               Buffer->getBufferStart(), BufferPos, Buffer->getBufferEnd());