[BUG] Missing braces in assignment operator when initialize vector with a list of values

[filipsajdak]

After f608b78 (done to fix #312). It broke the scenario described here: #312 (comment)

For the following code:

element: type = {
    children: std::vector<int> = (1,2,3);
    tab : std::vector<int>;

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

Cppfront will generate (skipping type declarations, type definitions and function declarations):

#line 5 "/Users/filipsajdak/dev/execspec/external/tests/bug_assignement_operator_4.cpp2"
    element::element(cpp2::in<int> t)
        : tab{ 3, 2, 1 }
#line 5 "/Users/filipsajdak/dev/execspec/external/tests/bug_assignement_operator_4.cpp2"
    {

    }
#line 5 "/Users/filipsajdak/dev/execspec/external/tests/bug_assignement_operator_4.cpp2"
    auto element::operator=(cpp2::in<int> t) -> element& {
        children = 1, 2, 3;
        tab = 3, 2, 1;
        return *this;

#line 7 "/Users/filipsajdak/dev/execspec/external/tests/bug_assignement_operator_4.cpp2"
    }

The issue is with element::operator=() that has the following lines:

        children = 1, 2, 3;
        tab = 3, 2, 1;

And will compile with the error (cut only the part that describes the problem):

../tests/bug_assignement_operator_4.cpp2:6:18: error: no viable overloaded '='
        children = 1, 2, 3;
        ~~~~~~~~ ^ ~
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/c++/v1/vector:444:13: note: candidate function not viable: no known conversion from 'int' to 'const std::vector<int>' for 1st argument
    vector& operator=(const vector& __x);
            ^
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/c++/v1/vector:454:13: note: candidate function not viable: no known conversion from 'int' to 'initializer_list<std::vector<int>::value_type>' (aka 'initializer_list<int>') for 1st argument
    vector& operator=(initializer_list<value_type> __il)
            ^
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/c++/v1/vector:469:13: note: candidate function not viable: no known conversion from 'int' to 'std::vector<int>' for 1st argument
    vector& operator=(vector&& __x)
            ^
../tests/bug_assignement_operator_4.cpp2:7:13: error: no viable overloaded '='
        tab = 3, 2, 1;
        ~~~ ^ ~

Changing problematic lines to the following:

        children = {1, 2, 3};
        tab = {3, 2, 1};

Fixes the issue.

[filipsajdak]

I did a dirty fix to that (I don't know yet how to test if the initializer has expression_list_node, so I check if emitted initializer has a comma ,).

diff --git a/source/cppfront.cpp b/source/cppfront.cpp
index 816f5be..45c2a60 100644
--- a/source/cppfront.cpp
+++ b/source/cppfront.cpp
@@ -4321,11 +4321,13 @@ public:
                     }
                     out_inits = {};
 
+                    auto found_expression_list = initializer.find(',') != initializer.npos;
+
                     current_functions.back().prolog.statements.push_back(
                         (*object)->name()->to_string(true) +
-                        " = " +
+                        " = " + (found_expression_list ? "{" : "") +
                         initializer +
-                        ";"
+                        (found_expression_list ? "}" : "") + ";"
                     );
                 }
                 //  (b) ... if this isn't assignment, only need to emit it if it was
@@ -4393,12 +4395,12 @@ public:
                         if (initializer.empty()) {
                             initializer = "{}";
                         }
-
+                        auto found_expression_list = initializer.find(',') != initializer.npos;
                         current_functions.back().prolog.statements.push_back(
                             (*object)->name()->to_string(true) +
-                            " = " +
+                            " = " + (found_expression_list ? "{" : "") +
                             initializer +
-                            ";"
+                            (found_expression_list ? "}" : "")+ ";"
                         );
                     }
                 }

The dirty fix works. Maybe you know a better way of checking if initializer (statement_node) has expression_list_node?

[basic-bro]

If I've read the source correctly, initializer in this case is set on line 4263 with:

initializer = print_to_string( *exprs.rhs );

Now, the member .rhs has type logical_or_expression_node*, which does not reach an expression_list_node going down the binary_expression_node tree. This is unlike the .lhs member, which has type postfix_expression_node*, whose tree includes expression_list_node via the primary_expression_node expr pointer member or via the ops member vector of type term.

Hence, perhaps changing the type of the .rhs member in the assignment_expression_lhs_rhs struct is a way forward?