[clangd] findNearbyIdentifier(): fix the word search in the token stream.

Without this patch the word occurrence search always returns the first token of the file.
Despite of that, `findNeardyIdentifier()` returns the correct result (but inefficently) until there are several matched tokens with the same value `floor(log2(<token line> - <word line>))` (e.g. several matched tokens on the same line).

Reviewed By: kadircet

Differential Revision: https://reviews.llvm.org/D84912

clang-tools-extra/clangd/XRefs.cpp

@@ -518,7 +518,7 @@ const syntax::Token *findNearbyIdentifier(const SpelledWord &Word,
   // Find where the word occurred in the token stream, to search forward & back.
   auto *I = llvm::partition_point(SpelledTokens, [&](const syntax::Token &T) {
     assert(SM.getFileID(T.location()) == SM.getFileID(Word.Location));
-    return T.location() >= Word.Location; // Comparison OK: same file.
+    return T.location() < Word.Location; // Comparison OK: same file.
   });
   // Search for matches after the cursor.
   for (const syntax::Token &Tok : llvm::makeArrayRef(I, SpelledTokens.end()))

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

@@ -1197,7 +1197,14 @@ TEST(LocateSymbol, NearbyIdentifier) {
 
       // h^i
     )cpp",
-  };
+      R"cpp(
+      // prefer nearest occurrence even if several matched tokens
+      // have the same value of `floor(log2(<token line> - <word line>))`.
+      int hello;
+      int x = hello, y = hello;
+      int z = [[hello]];
+      // h^ello
+    )cpp"};
   for (const char *Test : Tests) {
     Annotations T(Test);
     auto AST = TestTU::withCode(T.code()).build();