Can't use an operator shadowed by a variable of the same name as the aliasee

```purescript
f :: Int -> Int -> Int
f = (+)

infixl 6 f as %

g :: Int -> Int -> Int
g a b = let f = (-) in a % b
```

Should be functionally equivalent to:

```purescript
f :: Int -> Int -> Int
f = (+)

infixl 6 f as %

g :: Int -> Int -> Int
g = f
```

Instead, I get the error:

<pre>  Value f is undefined.

while inferring the type of f
in value declaration g</pre>