[clangd] Fix a crash in Selection

[ilya-biryukov]

Summary

The assertion checking that a range of a node is a token range does
not hold in case of "split" tokens, e.g. between two closing template
argument lists (vector<vector<int>>).

[ilya-biryukov]

• Fix a syntax error in the test

[kadircet]

LGTM

clang-tools-extra/clangd/Selection.cpp

bool nodesCoverRange(llvm::ArrayRef<const Node *> Nodes, unsigned Begin,
     // Collect all the expansion ranges, as offsets.
     SmallVector<std::pair<unsigned, unsigned>, 8> ChildRanges;
     for (const Node *N : Nodes) {
       CharSourceRange R = SM.getExpansionRange(N->ASTNode.getSourceRange());
       auto B = SM.getDecomposedLoc(R.getBegin());
       auto E = SM.getDecomposedLoc(R.getEnd());
       if (B.first != SelFile || E.first != SelFile)
         continue;
-      assert(R.isTokenRange());
       // Try to cover up to the next token, spaces between children don't count.
       if (auto Tok = Lexer::findNextToken(R.getEnd(), SM, LangOpts))
         E.second = SM.getFileOffset(Tok->getLocation());
-      else
+      else if (R.isTokenRange())
         E.second += Lexer::MeasureTokenLength(R.getEnd(), SM, LangOpts);
       ChildRanges.push_back({B.second, E.second});
     }
     llvm::sort(ChildRanges);
 
     // Scan through the child ranges, removing as we go.
     for (const auto R : ChildRanges) {
       if (R.first > Begin)

clang-tools-extra/unittests/clangd/SelectionTests.cpp

const char *Cases[] = {
       R"cpp(
         void foo() {
           [[if ([[1^11]]) $C[[{
             $C[[return]];
           }]] else [[{^
           }]]]]
         }
       )cpp",
+      R"cpp(
+          template <class T>
+          struct unique_ptr {};
+          void foo(^$C[[unique_ptr<unique_ptr<$C[[int]]>>]]^ a) {}
+      )cpp",
   };
   for (const char *C : Cases) {
     Annotations Test(C);
     auto AST = TestTU::withCode(Test.code()).build();
     auto T = makeSelectionTree(C, AST);
 
     std::vector<Range> Complete, Partial;
     for (const SelectionTree::Node *N : allNodes(T))