Open Radar

 
Summary:
The following code gives a wrong or misleading error

let myArr = [[1, 2, 3, 4],[1, 2, 4, 8],[2, 3, 5, 7]]

let output = myArr.flatMap { value in
    print("value is ", value)
    return value
}

print("output: ), output)

Steps to Reproduce:
Enter the above code in a Playground.

Expected Results:
I expected the output to be 
value is  [1, 2, 3, 4]
value is  [1, 2, 4, 8]
value is  [2, 3, 5, 7]
output:  [1, 2, 3, 4, 1, 2, 4, 8, 2, 3, 5, 7]


Actual Results:
The above code produces the error

Playground execution failed: /var/folders/cl/d10fdkcx7kv5bjgrfg8x3gy40000gn/T/./lldb/12716/playground486.swift:27:20: error: cannot invoke 'flatMap' with an argument list of type '((_) -> _)'
let output = myArr.flatMap { value in
                   ^
/var/folders/cl/d10fdkcx7kv5bjgrfg8x3gy40000gn/T/./lldb/12716/playground486.swift:27:20: note: overloads for 'flatMap' exist with these partially matching parameter lists: ((Self.Generator.Element) throws -> S), (@noescape (Self.Generator.Element) throws -> T?)
let output = myArr.flatMap { value in


Regression:
This happens in all configurations.

Notes:
Commenting out the `return value` line causes the code to be correctly interpreted and prints the expected values.
Commenting out the `print("value is ",value)` line also causes the code to be correctly interpreted and produces the expected output.