## 锁存器检测(Latch detected)

### 一、简介

SpinalHDL会检查在综合时没有组合逻辑信号会引入锁存器。换句话说, 这是检查没有组合信号被部分赋值。

### 二、例子

下述代码：
```Scala
class TopLevel extends Component {
  val cond = in(Bool)
  val a = UInt(8 bits)

  when(cond) {
    a := 42
  }
}
```
会产生如下报错：
```
LATCH DETECTED from the combinatorial signal (toplevel/a :  UInt[8 bits]), defined at
  ***
  Source file location of the toplevel/io_a definition via the stack trace
  ***
```
修复为：
```Scala
class TopLevel extends Component {
  val cond = in(Bool)
  val a = UInt(8 bits)

  a := 0
  when(cond) {
    a := 42
  }
}
```