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Issue Description:

Observed Behavior: When a function parameter is a tuple containing one or more closure signatures, pressing Return while its placeholder is highlighted in Xcode's source editor produces incorrect code template expansion. All other parameters in the tuple are ignored. If the closure signatures have an empty (()) input pattern, then only the first closure found is expanded. If the the closures expect an input value, then those input values are erroneously aggregated and applied to a single expanded closure.

Expected behavior: The expansion should expand the tuple's signature completely, and for any closures it encounters it should produce fully labelled and parameterized closure structures.

Example 1:

func someMethod(closures: (closure1: () -> Void,
                           closure2: () -> Void)) { }

incorrectly expands as:

someMethod {
    <#code#>
}

but should expand as:

someMethod(closures: (closure1: {
    <#code#>
}, closure2: {
    <#code#>
}))

Example 2:

func someMethod(closures: (int: Int,
                           closure1: (Double) -> Data,
                           closure2: (String, Int) -> Float32)) { }

incorrectly expands as:

someMethod { (<#Double#>, <#String#>, <#Int#>) -> Float32 in
    <#code#>
}

but should expand as:

someMethod(closures: (int: <#Int#>, closure1: { (<#Double#>) -> Data in
    <#code#>
}, closure2: { (<#String#>, <#Int#>) -> Float32 in
    <#code#>
}))