Swift 2b3: Incongruous `unexpected trailing closure` error in `init` function which is cast and called without trailing closure.

Originator:jdhealy
Number:rdar://21784170 Date Originated:12-Jul-2015 12:17 AM
Status:Open Resolved:
Product:Developer Tools Product Version:/Applications/Xcode-7A152u.app
Classification:Other Bug Reproducible:Always
 
Summary:
Incongruous `unexpected trailing closure` error in `init` function which is cast and called without (trailing or non-trailing) closure.

Steps to Reproduce:

- Paste into command line:

```
swift <<-EOF
let initial = (1.0 as Double, 2.0 as Double)
(Array.init as (Double...) -> Array<Double>)(initial as (Double, Double))
EOF
```

Expected Results:

```
Welcome to Apple Swift version 2.0 (700.0.45 700.0.57.2). Type :help for assistance.
initial: (Double, Double) = {
  0 = 1
  1 = 2
}
$R0: [Double] = 2 values {
  [0] = 1
  [1] = 2
}
```

Actual Results:

```
Welcome to Apple Swift version 2.0 (700.0.45 700.0.57.2). Type :help for assistance.
initial: (Double, Double) = {
  0 = 1
  1 = 2
}
repl.swift:2:13: error: unexpected trailing closure
(Array.init as (Double...) -> Array<Double>)(initial as (Double, Double))
            ^

```

Notes:

The following code block compiles and produces the expected output:

```
swift <<-EOF
let initial = (1.0 as Double, 2.0 as Double)
(Array.init as (Double...) -> Array<Double>)(1.0, 2.0)
EOF
```

The following two code blocks fail with the same `repl.swift:2:13: error: unexpected trailing closure` error as the topmost code block:

```
swift <<-EOF
let initial = (1.0 as Double, 2.0 as Double)
(Array.init as (Double...) -> Array<Double>)(initial)
EOF
```

```
swift <<-EOF
let initial = (1.0 as Double, 2.0 as Double)
(Array.init as (Double...) -> Array<Double>)(
	Optional(
		initial as (Double, Double)
	)!
)
EOF
```

Comments

Update 2

The error given by swiftlang_PONDEROSA-700.1.100.2 is much better than in swiftlang-700.0.52.1 — much appreciated, Swift Team! 👏🏼👏🏼👏🏼 

/Applications/Xcode-7B60.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift <<-EOF
let initial = (1.0 as Double, 2.0 as Double)
(Array.init as (Double...) -> Array<Double>)(initial as (Double, Double))
EOF
error: libarclite_macosx.a(arclite.o) failed to load objfile for /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/arc/libarclite_macosx.a
Welcome to Apple Swift version 2.0 (700.1.100.2 700.1.74). Type :help for assistance.
initial: (Double, Double) = {
  0 = 1
  1 = 2
}
repl.swift:2:54: error: cannot convert value of type '(Double, Double)' to expected argument type '[Double]'
(Array.init as (Double...) -> Array<Double>)(initial as (Double, Double))
                                             ~~~~~~~~^~~~~~~~~~~~~~~~~~~

Still, the first code block seems like it should compile and return the expected outcome, especially because the following does: 

/Applications/Xcode-7B60.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift <<-EOF
(Array.init as (Double...) -> Array<Double>)(1.0, 2.0)
EOF

Thanks for all the hard work!

By jdhealy at Sept. 24, 2015, 3:46 p.m. (reply...)

Update

/Applications/Xcode-7A176x.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift <<-EOF
let initial = (1.0 as Double, 2.0 as Double)
(Array.init as (Double...) -> Array<Double>)(initial as (Double, Double))
EOF

Outputs: 

Welcome to Apple Swift version 2.0 (700.0.52.1 700.0.65). Type :help for assistance.
initial: (Double, Double) = {
  0 = 1
  1 = 2
}
repl.swift:2:46: error: cannot invoke value of type '(Double...) -> Array<Double>' with argument list '(Double, Double)'
(Array.init as (Double...) -> Array<Double>)(initial as (Double, Double))
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^

So, thankfully, the nonsensical trailing closure error is gone, but shouldn't that invocation work? Ideally, the expected output would be: 

Welcome to Apple Swift version 2.0 (700.0.45 700.0.57.2). Type :help for assistance.
initial: (Double, Double) = {
  0 = 1
  1 = 2
}
$R0: [Double] = 2 values {
  [0] = 1
  [1] = 2
}

Also, tried: 

/Applications/Xcode-7A176x.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift <<-EOF
let initial = (1.0 as Double, 2.0 as Double)
(Array.init as (Double...) -> Array<Double>)(initial as (Double...))
EOF
Welcome to Apple Swift version 2.0 (700.0.52.1 700.0.65). Type :help for assistance.
initial: (Double, Double) = {
  0 = 1
  1 = 2
}
repl.swift:2:64: error: cannot create a variadic tuple
(Array.init as (Double...) -> Array<Double>)(initial as (Double...))
                                                               ^
repl.swift:2:54: error: '(Double, Double)' is not convertible to '(Double)'
(Array.init as (Double...) -> Array<Double>)(initial as (Double...))
                                             ~~~~~~~~^~~~~~~~~~~~~~
By jdhealy at Aug. 10, 2015, 5:49 p.m. (reply...)

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