Migrate Declarators to use the List API

After this change all nodes that have a delimited-list are using the
`List` API.

Implementation details:
Let's look at a declaration with multiple declarators:
`int a, b;`
To generate a declarator list node we need to have the range of
declarators: `a, b`:
However, the `ClangAST` actually stores them as separate declarations:
`int a   ;`
`int    b;`
We solve that by appropriately marking the declarators on each separate
declaration in the `ClangAST` and then for the final declarator `int
b`, shrinking its range to fit to the already marked declarators.

Differential Revision: https://reviews.llvm.org/D88403

1 files changed, 63 insertions, 6 deletions

diff --git a/clang/lib/Tooling/Syntax/BuildTree.cpp b/clang/lib/Tooling/Syntax/BuildTree.cpp
index 4d36509..e1ed55f 100644
--- a/clang/lib/Tooling/Syntax/BuildTree.cpp
+++ b/clang/lib/Tooling/Syntax/BuildTree.cpp
@@ -397,6 +397,17 @@ public:
       Mapping.add(From, New);
   }
 
+  /// Populate children for \p New list, assuming it covers tokens from a
+  /// subrange of \p SuperRange.
+  void foldList(ArrayRef<syntax::Token> SuperRange, syntax::List *New,
+                ASTPtr From) {
+    assert(New);
+    auto ListRange = Pending.shrinkToFitList(SuperRange);
+    Pending.foldChildren(Arena, ListRange, New);
+    if (From)
+      Mapping.add(From, New);
+  }
+
   /// Notifies that we should not consume trailing semicolon when computing
   /// token range of \p D.
   void noticeDeclWithoutSemicolon(Decl *D);
@@ -579,6 +590,35 @@ private:
       It->second->setRole(Role);
     }
 
+    /// Shrink \p Range to a subrange that only contains tokens of a list.
+    /// List elements and delimiters should already have correct roles.
+    ArrayRef<syntax::Token> shrinkToFitList(ArrayRef<syntax::Token> Range) {
+      auto BeginChildren = Trees.lower_bound(Range.begin());
+      assert((BeginChildren == Trees.end() ||
+              BeginChildren->first == Range.begin()) &&
+             "Range crosses boundaries of existing subtrees");
+
+      auto EndChildren = Trees.lower_bound(Range.end());
+      assert(
+          (EndChildren == Trees.end() || EndChildren->first == Range.end()) &&
+          "Range crosses boundaries of existing subtrees");
+
+      auto BelongsToList = [](decltype(Trees)::value_type KV) {
+        auto Role = KV.second->getRole();
+        return Role == syntax::NodeRole::ListElement ||
+               Role == syntax::NodeRole::ListDelimiter;
+      };
+
+      auto BeginListChildren =
+          std::find_if(BeginChildren, EndChildren, BelongsToList);
+
+      auto EndListChildren =
+          std::find_if_not(BeginListChildren, EndChildren, BelongsToList);
+
+      return ArrayRef<syntax::Token>(BeginListChildren->first,
+                                     EndListChildren->first);
+    }
+
     /// Add \p Node to the forest and attach child nodes based on \p Tokens.
     void foldChildren(const syntax::Arena &A, ArrayRef<syntax::Token> Tokens,
                       syntax::Tree *Node) {
@@ -1513,14 +1553,31 @@ private:
 
     // There doesn't have to be a declarator (e.g. `void foo(int)` only has
     // declaration, but no declarator).
-    if (Range.getBegin().isValid()) {
-      auto *N = new (allocator()) syntax::SimpleDeclarator;
-      Builder.foldNode(Builder.getRange(Range), N, nullptr);
-      Builder.markChild(N, syntax::NodeRole::Declarator);
+    if (!Range.getBegin().isValid()) {
+      Builder.markChild(new (allocator()) syntax::DeclaratorList,
+                        syntax::NodeRole::Declarators);
+      Builder.foldNode(Builder.getDeclarationRange(D),
+                       new (allocator()) syntax::SimpleDeclaration, D);
+      return true;
     }
 
-    if (Builder.isResponsibleForCreatingDeclaration(D)) {
-      Builder.foldNode(Builder.getDeclarationRange(D),
+    auto *N = new (allocator()) syntax::SimpleDeclarator;
+    Builder.foldNode(Builder.getRange(Range), N, nullptr);
+    Builder.markChild(N, syntax::NodeRole::ListElement);
+
+    if (!Builder.isResponsibleForCreatingDeclaration(D)) {
+      // If this is not the last declarator in the declaration we expect a
+      // delimiter after it.
+      const auto *DelimiterToken = std::next(Builder.findToken(Range.getEnd()));
+      if (DelimiterToken->kind() == clang::tok::TokenKind::comma)
+        Builder.markChildToken(DelimiterToken, syntax::NodeRole::ListDelimiter);
+    } else {
+      auto *DL = new (allocator()) syntax::DeclaratorList;
+      auto DeclarationRange = Builder.getDeclarationRange(D);
+      Builder.foldList(DeclarationRange, DL, nullptr);
+
+      Builder.markChild(DL, syntax::NodeRole::Declarators);
+      Builder.foldNode(DeclarationRange,
                        new (allocator()) syntax::SimpleDeclaration, D);
     }
     return true;