Sometimes incorrect parse of C(C&)

[paul-j-lucas]

A declaration like:

c++decl> explain C(C const&)
declare C as constructor (reference to constant C)

(where C has not been predeclared) works because the lexer returns C as a NAME and the parser matches it here:

pc99_func_or_constructor_decl_c
  : Y_NAME '(' param_list_c_ast_opt ')' noexcept_c_stid_opt func_equals_c_stid_opt

In C++, a NAME followed by ( declares an in-class constructor, so we interpret it as such.

However, if C is predeclared, then it doesn't work:

c++decl> class C
c++decl> explain C(C const&)
                          ^
12: syntax error: "&": ')' expected

The reason is because the lexer returns C as a type name and the parser tries to match it here:

typed_declaration_c
  : type_c_ast decl_list_c_opt

as an ordinary typed declaration (which is wrong). The reason is because C++ grammar is ambiguous:

C(x)    // declare x as C (with unnecessary parentheses)
C(C&)   // declare C as constructor

There's no easy fix for this.