fix(cpp): a call on a dereferenced iterator or pointer, (*it)->Visit(), calls the method of what it points at

[colbymchenry]

Summary

This is the follow-up left after #2579: calls through a dereference.

The extractor records (*it)->Visit() and (*node).Weight() by their bare names, because it can't spell a (*name) receiver. The name strategies then gave those calls to whichever class had a method of that name, at confidence 0.4–0.7. Examples:

• protobuf's (*iter)->number() over const FieldDescriptor* went to the C# generator's FieldGeneratorBase::number;
• rocksdb's (*range_tombstone_iter_)->SeekToFirst() went to the caller's own LevelIterator.

Separately, a local set by a dereference, auto first = *nodes.begin(), had no type.

What changed:

• cppDereferenced: *x and x-> in C++ expression typing now dereference a container's iterator to its element, as well as pointers and holders. It's used by cppExpressionType, cppMemberObject and cppChainInnerType. This types:

  • auto first = *nodes.begin();
  • auto& wal = *it;
  • structured bindings over *it;
  • -> through iterators in chains and initializers (it->Child()->Visit()).

  The iterator part is fix(cpp): a -> call on a declared container iterator calls the element's method #2576's element reading, factored out as cppIteratorTarget.

• matchCppDereferencedCall, which runs before the name strategies: a bare-name call written on (*name) is resolved on the dereferenced value's class by C++ lookup.

  • The receiver is read at the call's column, where it starts. cppUtf8Column is factored out of cppImplicitReceiver for that.
  • The result is the method, or no project method for a library type, a template parameter's, or a class that surely lacks the method.
  • Anything else goes on as before.

Validation

• New test __tests__/cpp-dereferenced-iterator-calls.test.ts (4 tests): all 4 fail on main and pass here.
• Mutations: switching off each part fails its test:
  • *x on iterators: 3 tests;
  • x-> in expressions: 1;
  • x-> in chains: 1;
  • the dereferenced-call matcher: 3;
  • "a library type calls nothing": 1.
• A/B (full index, main vs fix) on google/leveldb, fmtlib/fmt, redis (C control), facebook/rocksdb and protocolbuffers/protobuf. Every site was triaged, and all changes are correct.
  • leveldb (2), fmt (1): metadata-only. (*table)->ReadMeta, (*ptr)->key() and (*captured_stream)->… through double pointers keep their target, typed at 0.9.
  • rocksdb:
    • 9 added: (*it)->Name() reaches ReadOnlyMemTable; (*pointer)->GetOptions<…> reaches Configurable; (*txn)->Put reaches Transaction; (*builder)->Finish reaches BlockBuilder; 5 × bfile->PathName() on auto bfile = *iter reach BlobFile.
    • 28 retargeted from 0.4/0.7 guesses to the typed class. Examples: (*log_writer)->AddRecord now reaches log::Writer rather than BlobLogWriter; (*r)->use_direct_io() reaches FSSequentialFile, FSWritableFile and FSRandomAccessFile; (*txn)->Commit reaches Transaction rather than PendingExpectedValue.
    • One retarget is an overload: range_del_agg->ShouldDelete(test_case.lookup_key, …), where test_case = *it, now picks the ParsedInternalKey overload, as main already does for the identical range-for loop above it.
    • 8 removed, all wrong guesses on library or template-parameter types: (*handle).reset() on a std::unique_ptr*; (*id).data() on a std::array alias; (*lk).lock()/unlock(); two (*result)->IsInstanceOf on U** in a template.
    • 38 metadata-only: same targets, confidence up to 0.9. This includes the census's auto first_cfd = *compaction_queue_.begin().
  • protobuf:
    • 6 retargeted: (*lhs_sub)->GetReflection()/New/CopyFrom on Message** now reach Message rather than Any; (*target)->GetPrototype() on a const TypeInfo** reaches TypeInfo rather than the caller's own class.
    • 5 removed: 4 × (*iter)->number() over const FieldDescriptor*, whose accessors aren't indexed, had reached the C# generator; child_ptr.get() on a std::unique_ptr bound from *it had reached python's ScopedPythonPtr::get.
    • 7 metadata-only.
  • redis: byte-identical.
• Full suite, including every C/C++ test file: 7,150 passed, 0 failed.

Remaining, out of scope: map iterators' it->second.m(), which needs std::pair members; and other receivers the extractor can't spell (arr_[0].Foo(), this->p_->Foo()).

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