dillon1000/react

[test][ssa] Add todo test for reassigning in rval

From my understanding, `LeaveSSA` is not currently handling reassignment in 
rvals. 

Source code 

```js 

let x = foo(); 

x(x = bar()); 

``` 

Simplified HIR (from EnterSSA) 

``` 

[1]  $1 = StoreLocal Let x$0 = [[ foo() ]]       // x$1 = foo() 

[2] $2 = LoadLocal x$1                           // t0 = x$1 

[3] $4 = StoreLocal Reassign x$3 = [[ bar() ]]   // t1 = x$3 = bar() 

[4] $5 = CallExpression $2 ($4)                   // t0(t1) 

``` 

codegen: 

```js 

let x; 

x = foo(); 

x = bar(); 

x(x); 

```