# Bug when testing if a matrix is in SR

On sagemath 8.9, I find the behavior of `SR`

with matrix a bit strange.

```
sage: M = matrix([[0, -1], [1, 0]])
sage: print(SR(M)+M)
[[ 0 -1]
[ 1 0] -1]
[ 1 [ 0 -1]
[ 1 0]]
```

What is the use of coercing a matrix to the symbolic ring if it cannot be used as a matrix afterward?

These two lines of code also both raise an attribute error:

```
sage: SR(M) == M
sage: M in SR
AttributeError: 'ComplexIntervalField_class_with_category' object has no attribute 'complex_field'
```

By itself, it is not very relevant, but some element constructors (e.g. `lie_algebra`

) contain a line

```
if x in self.base_ring():
do something
```

which means `SR`

cannot be used as a base ring.

Is this a known bug?

A workaround would be to add a single line in `SR.__contains__`

to return false when `x`

is matrix (or maybe there are case when a matrix is considered in `SR`

, I don't know), but this would not solve the underlying issues.