go - channel 上的 cap() 不是常量？

Question

ch := make(chan int, 10)
fmt.Println(cap(ch))

函数调用 cap(ch) 常量 还是求值？

golang 规范说:

The expression len(s) is constant if s is a string constant. The expressions len(s) and cap(s) are constants if the type of s is an array or pointer to an array and the expression s does not contain channel receives or (non-constant) function calls; in this case s is not evaluated. Otherwise, invocations of len and cap are not constant and s is evaluated.

似乎已评估。

Answer 1

是的，cap() 在应用于 channel 时不是常量，因为 channel 的容量未编码为类型，因此在编译时未知。