[BUG] Type with a member and defined operator=: (out this, t : int ) produces an assignment operator with an initializer list

[filipsajdak]

In the current implementation of cppfront (fbf55ad) the following code:

element: type = {
    children: std::vector<int> = ();

    operator=: (out this, t : int ) = {
    }
}

Generates:

#define CPP2_USE_MODULES         Yes

#include "cpp2util.h"


#line 1 "../tests/bug_assignement_operator.cpp2"
class element;

//=== Cpp2 definitions ==========================================================

#line 1 "../tests/bug_assignement_operator.cpp2"
class element  {
    private: std::vector<int> children {}; 

    public: explicit element(cpp2::in<int> t){
    }
#line 4 "../tests/bug_assignement_operator.cpp2"
    public: auto operator=(cpp2::in<int> t) -> element& 
    : children{  }
#line 5 "../tests/bug_assignement_operator.cpp2"
{   
    return *this;
#line 6 "../tests/bug_assignement_operator.cpp2"
}};

The issue is that the assignment operator has an initializer list and fails to compile with the error:

../tests/bug_assignement_operator.cpp2... ok (all Cpp2, passes safety checks)

../tests/bug_assignement_operator.cpp2:5:5: error: only constructors take base initializers
    : children{  }
    ^
1 error generated.

[filipsajdak]

Similarly to #291 you can make this work by resigning from using the default initializer. The following code works:

element: type = {
    children: std::vector<int>;

    operator=: (out this, t : int ) = {
        children = std::vector<int>();
    }
}

also it is worth noting that I would prefer to write:

    operator=: (out this, t : int ) = {
        children = (1,2,3);
    }

to initialize children with values 1,2,3. Unfortunately that generates to the following code:

    public: explicit element(cpp2::in<int> t)
        : children{ 1, 2, 3 }
#line 5 "../tests/bug_assignement_operator.cpp2"
{
    }
#line 4 "../tests/bug_assignement_operator.cpp2"
    public: auto operator=(cpp2::in<int> t) -> element& {
        children = 1, 2, 3;
#line 5 "../tests/bug_assignement_operator.cpp2"
        
        return *this;
#line 6 "../tests/bug_assignement_operator.cpp2"
    }

Constructor is fine - it is using initializer list to initialize the vector with 1,2,3. The assignment is bad:

        children = 1, 2, 3;

Workaround for this will be using:

        children = std::vector<int>(1,2,3);

That will generate:

class element  {
    private: std::vector<int> children {}; 

    public: explicit element(cpp2::in<int> t)
        : children{ std::vector<int>(1, 2, 3) }
#line 4 "/Users/filipsajdak/dev/execspec/external/tests/bug_assignement_operator.cpp2"
                                    {

    }
#line 4 "/Users/filipsajdak/dev/execspec/external/tests/bug_assignement_operator.cpp2"
    public: auto operator=(cpp2::in<int> t) -> element& {
        children = std::vector<int>(1, 2, 3);
        return *this;
#line 6 "/Users/filipsajdak/dev/execspec/external/tests/bug_assignement_operator.cpp2"
    }
};

[hsutter]

Thanks! Fixed.

See also the comment in the closing commit for more information about a Clang warning that my fix now generates, but that I think is spurious.

[filipsajdak]

@hsutter I confirmed. The issue is solved!

The warning also appears with my compiler:

../tests/bug_assignement_operator.cpp2:9:16: warning: braces around scalar initializer [-Wbraced-scalar-init]
        name = {"Element"};

Apple clang version 14.0.3 (clang-1403.0.22.14.1)
Target: arm64-apple-darwin22.3.0
Thread model: posix