Ensure that SourceFiles always have a backing buffer in the SourceManager

The "buffer ID" in a SourceFile, which is used to find the source file's
contents in the SourceManager, has always been optional. However, the
effectively every SourceFile actually does have a buffer ID, and the
vast majority of accesses to this information dereference the optional
without checking.

Update the handful of call sites that provided `nullopt` as the buffer
ID to provide a proper buffer instead. These were mostly unit tests
and testing programs, with a few places that passed a never-empty
optional through to the SourceFile constructor.

Then, remove optionality from the representation and accessors. It is
now the case that every SourceFile has a buffer ID, simplying a bunch
of code.

Author: DougGregor

include/swift/AST/SourceFile.h

@@ -156,9 +156,7 @@ class SourceFile final : public FileUnit {
   std::optional<StableHasher> InterfaceHasher;
 
   /// The ID for the memory buffer containing this file's source.
-  ///
-  /// May be -1, to indicate no association with a buffer.
-  int BufferID;
+  unsigned BufferID;
 
   /// The parsing options for the file.
   ParsingOptions ParsingOpts;
@@ -370,7 +368,7 @@ class SourceFile final : public FileUnit {
   /// \c #sourceLocation(file:) declarations.
   llvm::StringMap<SourceFilePathInfo> getInfoForUsedFilePaths() const;
 
-  SourceFile(ModuleDecl &M, SourceFileKind K, std::optional<unsigned> bufferID,
+  SourceFile(ModuleDecl &M, SourceFileKind K, unsigned bufferID,
              ParsingOptions parsingOpts = {}, bool isPrimary = false);
 
   ~SourceFile();
@@ -590,9 +588,7 @@ class SourceFile final : public FileUnit {
 
   /// The buffer ID for the file that was imported, or None if there
   /// is no associated buffer.
-  std::optional<unsigned> getBufferID() const {
-    if (BufferID == -1)
-      return std::nullopt;
+  unsigned getBufferID() const {
     return BufferID;
   }
 

include/swift/Frontend/Frontend.h

@@ -789,7 +789,7 @@ class CompilerInstance {
   /// Creates a new source file for the main module.
   SourceFile *createSourceFileForMainModule(ModuleDecl *mod,
                                             SourceFileKind FileKind,
-                                            std::optional<unsigned> BufferID,
+                                            unsigned BufferID,
                                             bool isMainBuffer = false) const;
 
   /// Creates all the files to be added to the main module, appending them to

include/swift/IDE/IDERequests.h

@@ -50,7 +50,7 @@ struct CursorInfoOwner {
     return !(lhs == rhs);
   }
   bool isValid() const {
-    return File && File->getBufferID() && Loc.isValid();
+    return File && Loc.isValid();
   }
 };
 
@@ -110,7 +110,7 @@ struct RangeInfoOwner {
   }
 
   bool isValid() const {
-    return File && File->getBufferID() && StartLoc.isValid() && EndLoc.isValid();
+    return File && StartLoc.isValid() && EndLoc.isValid();
   }
 };
 

include/swift/Migrator/ASTMigratorPass.h

@@ -41,7 +41,7 @@ class ASTMigratorPass {
   ASTMigratorPass(EditorAdapter &Editor, SourceFile *SF,
                   const MigratorOptions &Opts)
     : Editor(Editor), SF(SF), Opts(Opts), Filename(SF->getFilename()),
-      BufferID(SF->getBufferID().value()),
+      BufferID(SF->getBufferID()),
       SM(SF->getASTContext().SourceMgr), Diags(SF->getASTContext().Diags) {}
 };
 

lib/AST/ASTContext.cpp

@@ -6622,9 +6622,8 @@ void VarDecl::setOriginalWrappedProperty(VarDecl *originalProperty) {
 static bool isSourceLocInOrignalBuffer(const Decl *D, SourceLoc Loc) {
   assert(Loc.isValid());
   auto bufferID = D->getDeclContext()->getParentSourceFile()->getBufferID();
-  assert(bufferID.has_value() && "Source buffer ID must be set");
   auto &SM = D->getASTContext().SourceMgr;
-  return SM.getRangeForBuffer(*bufferID).contains(Loc);
+  return SM.getRangeForBuffer(bufferID).contains(Loc);
 }
 #endif
 

lib/AST/ASTScopeCreation.cpp

@@ -272,7 +272,7 @@ ASTSourceFileScope::ASTSourceFileScope(SourceFile *SF,
 
     if (SF->Kind == SourceFileKind::DefaultArgument) {
       auto genInfo = *SF->getASTContext().SourceMgr.getGeneratedSourceInfo(
-          *SF->getBufferID());
+          SF->getBufferID());
       parentLoc = ASTNode::getFromOpaqueValue(genInfo.astNode).getStartLoc();
       if (auto parentScope =
               findStartingScopeForLookup(enclosingSF, parentLoc)) {

lib/AST/ASTScopePrinting.cpp

@@ -43,13 +43,8 @@ void ASTScopeImpl::dump() const { print(llvm::errs(), 0, false); }
 void ASTScopeImpl::dumpOneScopeMapLocation(
     std::pair<unsigned, unsigned> lineColumn) {
   auto bufferID = getSourceFile()->getBufferID();
-  if (!bufferID) {
-    llvm::errs() << "***No buffer, dumping all scopes***";
-    print(llvm::errs());
-    return;
-  }
   SourceLoc loc = getSourceManager().getLocForLineCol(
-      *bufferID, lineColumn.first, lineColumn.second);
+      bufferID, lineColumn.first, lineColumn.second);
   if (loc.isInvalid())
     return;
 

lib/AST/ASTScopeSourceRange.cpp

@@ -203,17 +203,9 @@ SourceRange GenericParamScope::getSourceRangeOfThisASTNode(
 
 SourceRange ASTSourceFileScope::getSourceRangeOfThisASTNode(
     const bool omitAssertions) const {
-  if (auto bufferID = SF->getBufferID()) {
-    auto charRange = getSourceManager().getRangeForBuffer(*bufferID);
-    return SourceRange(charRange.getStart(), charRange.getEnd());
-  }
-
-  if (SF->getTopLevelItems().empty())
-    return SourceRange();
-
-  // Use the source ranges of the declarations in the file.
-  return SourceRange(SF->getTopLevelItems().front().getStartLoc(),
-                     SF->getTopLevelItems().back().getEndLoc());
+  auto bufferID = SF->getBufferID();
+  auto charRange = getSourceManager().getRangeForBuffer(bufferID);
+  return SourceRange(charRange.getStart(), charRange.getEnd());
 }
 
 SourceRange GenericTypeOrExtensionScope::getSourceRangeOfThisASTNode(

lib/AST/DiagnosticEngine.cpp

@@ -1759,9 +1759,7 @@ BufferIndirectlyCausingDiagnosticRAII::BufferIndirectlyCausingDiagnosticRAII(
     const SourceFile &SF)
     : Diags(SF.getASTContext().Diags) {
   auto id = SF.getBufferID();
-  if (!id)
-    return;
-  auto loc = SF.getASTContext().SourceMgr.getLocForBufferStart(*id);
+  auto loc = SF.getASTContext().SourceMgr.getLocForBufferStart(id);
   if (loc.isValid())
     Diags.setBufferIndirectlyCausingDiagnosticToInput(loc);
 }

lib/AST/Module.cpp

@@ -775,8 +775,8 @@ namespace {
     SourceManager *sourceMgr;
 
     bool operator()(SourceFile *lhs, SourceFile *rhs) const {
-      auto lhsRange = sourceMgr->getRangeForBuffer(*lhs->getBufferID());
-      auto rhsRange = sourceMgr->getRangeForBuffer(*rhs->getBufferID());
+      auto lhsRange = sourceMgr->getRangeForBuffer(lhs->getBufferID());
+      auto rhsRange = sourceMgr->getRangeForBuffer(rhs->getBufferID());
 
       std::less<const char *> pointerCompare;
       return pointerCompare(
@@ -785,7 +785,7 @@ namespace {
     }
 
     bool operator()(SourceFile *lhs, SourceLoc rhsLoc) const {
-      auto lhsRange = sourceMgr->getRangeForBuffer(*lhs->getBufferID());
+      auto lhsRange = sourceMgr->getRangeForBuffer(lhs->getBufferID());
 
       std::less<const char *> pointerCompare;
       return pointerCompare(
@@ -794,7 +794,7 @@ namespace {
     }
 
     bool operator()(SourceLoc lhsLoc, SourceFile *rhs) const {
-      auto rhsRange = sourceMgr->getRangeForBuffer(*rhs->getBufferID());
+      auto rhsRange = sourceMgr->getRangeForBuffer(rhs->getBufferID());
 
       std::less<const char *> pointerCompare;
       return pointerCompare(
@@ -835,8 +835,7 @@ void ModuleDecl::updateSourceFileLocationMap() {
   // First, add all of the source files with a backing buffer.
   for (auto *fileUnit : files) {
     if (auto sourceFile = dyn_cast<SourceFile>(fileUnit)) {
-      if (sourceFile->getBufferID())
-        sourceFileLocationMap->allSourceFiles.push_back(sourceFile);
+      sourceFileLocationMap->allSourceFiles.push_back(sourceFile);
     }
   }
 
@@ -872,7 +871,7 @@ SourceFile *ModuleDecl::getSourceFileContainingLocation(SourceLoc loc) {
   // in to see if it contains this.
   if (sourceFileLocationMap) {
     if (auto lastSourceFile = sourceFileLocationMap->lastSourceFile) {
-      auto range = sourceMgr.getRangeForBuffer(*lastSourceFile->getBufferID());
+      auto range = sourceMgr.getRangeForBuffer(lastSourceFile->getBufferID());
       if (range.contains(adjustedLoc))
         return lastSourceFile;
     }
@@ -888,7 +887,7 @@ SourceFile *ModuleDecl::getSourceFileContainingLocation(SourceLoc loc) {
     return nullptr;
 
   auto foundSourceFile = *found;
-  auto foundRange = sourceMgr.getRangeForBuffer(*foundSourceFile->getBufferID());
+  auto foundRange = sourceMgr.getRangeForBuffer(foundSourceFile->getBufferID());
   // Positions inside an empty file or at EOF should still be considered within
   // this file.
   if (!foundRange.contains(adjustedLoc) && adjustedLoc != foundRange.getEnd())
@@ -1192,7 +1191,7 @@ SourceRange SourceFile::getMacroInsertionRange() const {
     return SourceRange();
 
   auto generatedInfo =
-      *getASTContext().SourceMgr.getGeneratedSourceInfo(*getBufferID());
+      *getASTContext().SourceMgr.getGeneratedSourceInfo(getBufferID());
   auto origRange = generatedInfo.originalSourceRange;
   return {origRange.getStart(), origRange.getEnd()};
 }
@@ -1202,7 +1201,7 @@ CustomAttr *SourceFile::getAttachedMacroAttribute() const {
     return nullptr;
 
   auto genInfo =
-      *getASTContext().SourceMgr.getGeneratedSourceInfo(*getBufferID());
+      *getASTContext().SourceMgr.getGeneratedSourceInfo(getBufferID());
   return genInfo.attachedMacroCustomAttr;
 }
 
@@ -1211,7 +1210,7 @@ std::optional<MacroRole> SourceFile::getFulfilledMacroRole() const {
     return std::nullopt;
 
   auto genInfo =
-      *getASTContext().SourceMgr.getGeneratedSourceInfo(*getBufferID());
+      *getASTContext().SourceMgr.getGeneratedSourceInfo(getBufferID());
   switch (genInfo.kind) {
 #define MACRO_ROLE(Name, Description)               \
   case GeneratedSourceInfo::Name##MacroExpansion: \
@@ -1231,7 +1230,7 @@ SourceFile *SourceFile::getEnclosingSourceFile() const {
     return nullptr;
 
   auto genInfo =
-      *getASTContext().SourceMgr.getGeneratedSourceInfo(*getBufferID());
+      *getASTContext().SourceMgr.getGeneratedSourceInfo(getBufferID());
   auto sourceLoc = genInfo.originalSourceRange.getStart();
   return getParentModule()->getSourceFileContainingLocation(sourceLoc);
 }
@@ -1242,7 +1241,7 @@ ASTNode SourceFile::getNodeInEnclosingSourceFile() const {
     return nullptr;
 
   auto genInfo =
-      *getASTContext().SourceMgr.getGeneratedSourceInfo(*getBufferID());
+      *getASTContext().SourceMgr.getGeneratedSourceInfo(getBufferID());
   return ASTNode::getFromOpaqueValue(genInfo.astNode);
 }
 
@@ -1470,7 +1469,7 @@ SourceFile::getExternalRawLocsForDecl(const Decl *D) const {
   bool InGeneratedBuffer =
       !SM.rangeContainsTokenLoc(SM.getRangeForBuffer(BufferID), MainLoc);
   if (InGeneratedBuffer) {
-    int UnderlyingBufferID;
+    unsigned UnderlyingBufferID;
     std::tie(UnderlyingBufferID, MainLoc) =
         D->getModuleContext()->getOriginalLocation(MainLoc);
     if (BufferID != UnderlyingBufferID)
@@ -2108,8 +2107,8 @@ bool ModuleDecl::registerEntryPointFile(
     if (existingDecl) {
       existingDiagLoc = sourceFile->getMainDeclDiagLoc();
     } else {
-      if (auto bufID = sourceFile->getBufferID())
-        existingDiagLoc = getASTContext().SourceMgr.getLocForBufferStart(*bufID);
+      auto bufID = sourceFile->getBufferID();
+      existingDiagLoc = getASTContext().SourceMgr.getLocForBufferStart(bufID);
     }
   }
 
@@ -3296,10 +3295,8 @@ llvm::StringMap<SourceFilePathInfo>
 SourceFile::getInfoForUsedFilePaths() const {
   llvm::StringMap<SourceFilePathInfo> result;
 
-  if (BufferID != -1) {
-    result[getFilename()].physicalFileLoc =
-        getASTContext().SourceMgr.getLocForBufferStart(BufferID);
-  }
+  result[getFilename()].physicalFileLoc =
+      getASTContext().SourceMgr.getLocForBufferStart(BufferID);
 
   for (auto &vpath : VirtualFilePaths) {
     result[vpath.Item].virtualFileLocs.insert(vpath.Loc);
@@ -3433,9 +3430,9 @@ ModuleDecl::computeFileIDMap(bool shouldDiagnose) const {
 }
 
 SourceFile::SourceFile(ModuleDecl &M, SourceFileKind K,
-                       std::optional<unsigned> bufferID,
+                       unsigned bufferID,
                        ParsingOptions parsingOpts, bool isPrimary)
-    : FileUnit(FileUnitKind::Source, M), BufferID(bufferID ? *bufferID : -1),
+    : FileUnit(FileUnitKind::Source, M), BufferID(bufferID),
       ParsingOpts(parsingOpts), IsPrimary(isPrimary), Kind(K) {
   M.getASTContext().addDestructorCleanup(*this);
 
@@ -3643,8 +3640,6 @@ bool SourceFile::walk(ASTWalker &walker) {
 }
 
 StringRef SourceFile::getFilename() const {
-  if (BufferID == -1)
-    return "";
   SourceManager &SM = getASTContext().SourceMgr;
   return SM.getIdentifierForBuffer(BufferID);
 }