c++ - 以静态大小的数组作为参数的通用 lambda

Question

以下通用(多态)lambda 是否合法 C++14？

auto f = [](auto x[3]) {
    x[0];
    x[1];
    // etc.
};

GCC 和 Clang 4 接受代码，但 Visual Studio 2017 不接受。合法吗？

error C3318: 'auto [3]': an array cannot have an element type that contains 'auto'

Answer 1

这是非法的。

[dcl.array]/1 ，强调我的:

In a declaration T D where D has the form

D1 [ constant-expressionopt ] attribute-specifier-seqopt

and the type of the identifier in the declaration T D1 is “derived-declarator-type-list T”, then the type of the identifier of D is an array type; if the type of the identifier of D contains the auto type-specifier, the program is ill-formed.