---
title: IncomparableMapKey
layout: article
---
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```
IncomparableMapKey occurs when a map key type does not support the == and
!= operators.

Per the spec:
 "The comparison operators == and != must be fully defined for operands of
 the key type; thus the key type must not be a function, map, or slice."

Example:
 var x map[T]int

 type T []int
```