[clang] Simplify buildSyntaxTree API

[kbobyrev]

Summary

Follow-up on https://reviews.llvm.org/D88553#inline-837013

[sammccall]

clang/include/clang/Tooling/Syntax/BuildTree.h

21–22

we should update the comment for this...

/// This usually covers the whole TranslationUnitDecl, but can be restricted by the ASTContext's traversal scope.

[kbobyrev]

Update comment.

clang-tools-extra/clangd/SemanticSelection.cpp

 }
 
 // FIXME(kirillbobyrev): Collect comments, PP conditional regions, includes and
 // other code regions (e.g. public/private/protected sections of classes,
 // control flow statement bodies).
 // Related issue: https://github.com/clangd/clangd/issues/310
 llvm::Expected<std::vector<FoldingRange>> getFoldingRanges(ParsedAST &AST) {
   syntax::Arena A(AST.getSourceManager(), AST.getLangOpts(), AST.getTokens());
-  const auto *SyntaxTree =
-      syntax::buildSyntaxTree(A, *AST.getASTContext().getTranslationUnitDecl());
+  const auto *SyntaxTree = syntax::buildSyntaxTree(A, AST.getASTContext());
   return collectFoldingRanges(SyntaxTree, AST.getSourceManager());
 }
 
 } // namespace clangd
 } // namespace clang

clang/include/clang/Tooling/Syntax/BuildTree.h

 #include "clang/AST/Decl.h"
 #include "clang/Basic/TokenKinds.h"
 #include "clang/Tooling/Syntax/Nodes.h"
 #include "clang/Tooling/Syntax/Tree.h"
 
 namespace clang {
 namespace syntax {
 
 /// Build a syntax tree for the main file.
-syntax::TranslationUnit *buildSyntaxTree(Arena &A,
-                                         const clang::TranslationUnitDecl &TU);
+/// This usually covers the whole TranslationUnitDecl, but can be restricted by
+/// the ASTContext's traversal scope.
+syntax::TranslationUnit *buildSyntaxTree(Arena &A, ASTContext &Context);
 
 // Create syntax trees from subtrees not backed by the source code.
 
 // Synthesis of Leafs
 /// Create `Leaf` from token with `Spelling` and assert it has the desired
 /// `TokenKind`.
 syntax::Leaf *createLeaf(syntax::Arena &A, tok::TokenKind K,
                          StringRef Spelling);

clang/lib/Tooling/Syntax/BuildTree.cpp

 const syntax::Token *syntax::TreeBuilder::findToken(SourceLocation L) const {
   if (L.isInvalid())
     return nullptr;
   auto It = LocationToToken.find(L);
   assert(It != LocationToToken.end());
   return It->second;
 }
 
-syntax::TranslationUnit *
-syntax::buildSyntaxTree(Arena &A, const TranslationUnitDecl &TU) {
+syntax::TranslationUnit *syntax::buildSyntaxTree(Arena &A,
+                                                 ASTContext &Context) {
   TreeBuilder Builder(A);
-  BuildTreeVisitor(TU.getASTContext(), Builder).TraverseAST(TU.getASTContext());
+  BuildTreeVisitor(Context, Builder).TraverseAST(Context);
   return std::move(Builder).finalize();
 }

clang/unittests/Tooling/Syntax/TreeTestBase.cpp

BuildSyntaxTree(syntax::TranslationUnit *&Root,
       assert(this->Tokens);
     }
 
     void HandleTranslationUnit(ASTContext &Ctx) override {
       TB = std::make_unique<syntax::TokenBuffer>(std::move(*Tokens).consume());
       Tokens = nullptr; // make sure we fail if this gets called twice.
       Arena = std::make_unique<syntax::Arena>(Ctx.getSourceManager(),
                                               Ctx.getLangOpts(), *TB);
-      Root = syntax::buildSyntaxTree(*Arena, *Ctx.getTranslationUnitDecl());
+      Root = syntax::buildSyntaxTree(*Arena, Ctx);
     }
 
   private:
     syntax::TranslationUnit *&Root;
     std::unique_ptr<syntax::TokenBuffer> &TB;
     std::unique_ptr<syntax::Arena> &Arena;
     std::unique_ptr<syntax::TokenCollector> Tokens;
   };