Fix for operator recognition in cpp2 code sections.

[MaxSagebaum]

For the cpp2 file:

operator*: (v1: double, v2: double) -> _ = v1 * v2;

The cppfront command cppfront opMul.cpp2 -p produces the error:

opMul.cpp2(1,1): error: pure-cpp2 switch disables Cpp1 syntax

I took this as an opportunity to get familiar with the code of cppfront. The switch in starts_with_operator had the comments for the operators but the cases statements where missing.

With the missing cases added, the test file works now with cppfront.

I also checked all operators against the list in https://en.cppreference.com/w/cpp/language/operators

1. Additional missing operators: &=, |=
2. Operators that are checked but not defined: &&=, ||=
3. Other missing operators: ,, ->*, (), []

I added the operators in point 1. Should I remove the operators under point 2? Should I add the operators under point 3?

On a side note: Thanks for working on cpp2 and providing it to the public!

[JohelEGP]

I also checked all operators against the list in https://en.cppreference.com/w/cpp/language/operators

1. Additional missing operators: `&=`, `|=`

2. Operators that are checked but not defined: `&&=`, `||=`

3. Other missing operators: `,`, `->*`, `()`, `[]`

See also #387 (comment).

[JohelEGP]

operator*: (v1: double, v2: double) -> _ = v1 * v2;

That declaration works at type scope.

Perhaps the greater issue is that the parser that recognizes a Cpp2 declaration at the top-level
doesn't use the same logic for parsing identifiers as the parser within a Cpp2 declaration.

[MaxSagebaum]

Thanks for pointing out #387 (comment) most of it would be fixed when I also add a patch for point 2 and 3.

operator*: (v1: double, v2: double) -> _ = v1 * v2;

That declaration works at type scope.

Perhaps the greater issue is that the parser that recognizes a Cpp2 declaration at the top-level doesn't use the same logic for parsing identifiers as the parser within a Cpp2 declaration.

You are right, that one would not write this operator. My original test had a custom class as arguments. Nevertheless, cppfront identifies it on a global level as a cpp1 line and will copy it to the generated source. The cpp1 compiler will then complain about this line.

[JohelEGP]

By type scope, I meant in a type scope, not with UDT arguments.
Or more generally, within a Cpp2 declaration.
This should work, but doesn't: https://cpp2.godbolt.org/z/z9nEYo6ar.

t: type = { }
ns: namespace = {
operator*: (_: t) = { } // Recognized as Cpp2.
}
operator*: (_: t) = { } // Not recognized as Cpp2.
main: () = { }

build/_cppfront/main.cpp:19:1: error: 'operator*' does not name a type
   19 | operator*: (_: t) = { } // Not recognized as Cpp2.
      | ^~~~~~~~

[MaxSagebaum]

Yes, my fix takes care of

operator*: (_: t) = { } // Not recognized as Cpp2.