parseGlobalVarDecl

fn parseGlobalVarDecl(p: *Parse) !?Node.Index {
    const var_decl = try p.parseVarDeclProto() orelse return null;

    const init_node: ?Node.Index = switch (p.tokenTag(p.tok_i)) {
        .equal_equal => blk: {
            try p.warn(.wrong_equal_var_decl);
            p.tok_i += 1;
            break :blk try p.expectExpr();
        },
        .equal => blk: {
            p.tok_i += 1;
            break :blk try p.expectExpr();
        },
        else => null,
    };

    p.setVarDeclInitExpr(var_decl, .fromOptional(init_node));

    try p.expectSemicolon(.expected_semi_after_decl, false);
    return var_decl;
}