[BUG] Namespace-scope variable alias not rejected

[JohelEGP]

A variable alias has a deduced type. Such is prohibited for a namespace-scope variable (see #315 (comment)).
Phase 1 emits the definition, so perhaps they were never intended to be used at namespace scope.

Minimal reproducer (https://godbolt.org/z/sjoK8saP4):

v1g: == v0g;
v0g: i8 = 0;

Commands:

cppfront x.cpp2
clang++17 -std=c++2b -stdlib=libc++ -I $CPPFRONT_INCLUDE_DIR x.cpp

Expected result: A similar diagnostic to that of a global variable of deduced type.

Actual result and error:

Generated C++1.

//=== Cpp2 type declarations ====================================================


#include "cpp2util.h"


//=== Cpp2 type definitions and function declarations ===========================

#line 1 "/app/main.cpp2"
auto const& v1g = v0g;
extern cpp2::i8 v0g;
//=== Cpp2 function definitions =================================================


#line 2 "/app/main.cpp2"
cpp2::i8 v0g {0}; 

main.cpp2:1:19: error: use of undeclared identifier 'v0g'
auto const& v1g = v0g;
                  ^
1 error generated.

[JohelEGP]

These now lower to constexpr globals.