[llvm-dev] C++ compiler error I do not understand (original) (raw)

Paul C. Anagnostopoulos via llvm-dev llvm-dev at lists.llvm.org
Tue Mar 30 17:02:35 PDT 2021

I have the following situation with which I could use some enlightenment. As usual, the context is TableGen.

in class Record:

public:
   using AssertionTuple = std::tuple<SMLoc, Init *, Init *>;
...
   SmallVector<AssertionTuple, 0> Assertions;

then there exists:

   struct RecordsEntry {
     std::unique_ptr<Record> Rec;
     std::unique_ptr<ForeachLoop> Loop;
     std::unique_ptr<Record::AssertionTuple> Assertion;

     void dump() const;

     RecordsEntry() {}
     RecordsEntry(std::unique_ptr<Record> Rec) : Rec(std::move(Rec)) {}
     RecordsEntry(std::unique_ptr<ForeachLoop> Loop)
       : Loop(std::move(Loop)) {}
     RecordsEntry(std::unique_ptr<Record::AssertionTuple> Assertion)
// 4th constructor
       : Assertion(std::move(Assertion)) {}
   };

...

bool TGParser::addEntry(RecordsEntry E) { ...

Note that I expect to create a RecordsEntry by passing an AssertionTuple to addEntry and having the 4th constructor do the trick. The other three constructors all work fine. However, when I do this:

     Record::AssertionTuple tuple = std::make_tuple(ConditionLoc,
Condition, Message);
     addEntry(std::move(tuple));

I get this:

C:\LLVM\llvm-project\llvm\lib\TableGen\TGParser.cpp(3190): error
C2664: 'bool llvm::TGParser::addEntry(llvm::RecordsEntry)': cannot
convert argument 1 from 'llvm::Record::AssertionTuple' to
'llvm::RecordsEntry'
C:\LLVM\llvm-project\llvm\lib\TableGen\TGParser.cpp(3190): note: No
user-defined-conversion operator available that can perform this
conversion, or the operator cannot be called
C:\LLVM\llvm-project\llvm\lib\TableGen\TGParser.cpp(344): note: see
declaration of 'llvm::TGParser::addEntry'

Ah, I guess I should show the definitions of the three arguments passed to make_tuple() above:

   SMLoc ConditionLoc = Lex.getLoc();
   Init *Condition = ParseValue(CurRec);
   Init *Message = ParseValue(CurRec);

Since there is no complaint about making the tuple, I assume those three arguments have the correct type. The problem is the 4th RecordsEntry constructor, which cannot convert the addEntry argument 'std::move(tuple)' to a Record::AssertionTuple, even though that's exactly what it is.

P.S.: Regardless of what I learn here, I'm going to change the assertion tuple into a little struct, which should work fine as demonstrated by constructor 3 above.

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