Variable with generic type assigned to non-generic

[kyleheadley]

This happens in libarchive:

../libarchive/archive_read_support_format_lha.c:289:34: error (init_incompatible): initializing '_Array_ptr<const unsigned char>' with an expression of incompatible type '_Array_ptr<T>' (aka '_Array_ptr<(0, 0) __BoundsInterface>')
        _Array_ptr<const unsigned char> p : count(5 + 1) = h;
                                        ^                  ~

[kyleheadley]

This is allowed in ConstraintVariables.cpp:1865 as long as the generic var is compatible. We could disallow it there, but the problem is that generic functions require the argument (or an interface argument created by 3c) to match the parameter when one is wild and one is not. So we have to distinguish the context or recognize the interface variable. But the interface is a type variable from the generic type, not the full type. So it's used when constraining the type but not when constraining the argument to the param.

So our best solution at the moment is to recognize when the comparison happens at a generic function call site and allow some misuses of that.

[kyleheadley]

Work so far is in branch wild_concrete_equals_generic. It solves all the issues here, but there is one failure (pair) in vsftpd benchmark where a function recognized as generic doesn't have a type parameter. This needs to be debugged before a PR is posted.

ftppolicy.c:70:3: error (failed_expectation): expected a type argument list for a generic function call
  ptrace_sandbox_set_setsockopt_validator(p_sandbox, setsockopt_validator, 0);
  ^
ftppolicy.c:119:5: error (failed_expectation): expected a type argument list for a generic function call
    ptrace_sandbox_set_getsockopt_validator(p_sandbox, getsockopt_validator, 0);
    ^