Unexpected Interaction between Named Tuples and Context Functions

## Compiler version

3.7.3, 3.7.1

## Minimized code

```scala
def test(f: String ?=> Unit): Unit = ???

test(a = 1, b = 2)
```

## Output

Compiles. Seems to be equivalent to: `test { (a = 1, b = 2) }` Implicitly creating a named tuple.

## Expectation

Should not Compile.