[SR-5950] Passing closures to constructor works on Swift 3.1, fails on Swift 3.2

[swift-ci]

Previous ID	SR-5950
Radar	None
Original Reporter	kam (JIRA User)
Type	Bug

Environment

Xcode 9

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug, 4.0Regression, TypeChecker
Assignee	None
Priority	Medium

md5: 124233556cc025b223c538070e322846

Issue Description:

The following code compiles fine on Swift 3.1 in Xcode 8.3.3:

import Foundation

struct Calculator {

    let tCrit: Double
    let predictedValue: ([Double]) -> Double
}

// variable indices
let index1 = 0
let index2 = 1
let index3 = 2

let calc1 = Calculator(
    tCrit: 1.962,
    predictedValue: { (parameters: [Double]) -> Double in
        return -603 + 123.31 * parameters[index1] + 9.288 * parameters[index2] + 0.316 * parameters[index3]
}
)

let calc2 = Calculator(

    tCrit: 1.962,
    predictedValue: { parameters in
        -302.908 + 0.162 * parameters[index1] + 3.112 * parameters[index2] + 0.392 * parameters[index3]
})

let calc3 = Calculator(

    tCrit: 1.962,
    predictedValue: { parameters in
        -992 + 1.312 * parameters[index1] + 1.235 * parameters[index2]
})

let calc4 = Calculator(

    tCrit: 1.962,
    predictedValue: { parameters in
        -2932.32 + 1.253 * parameters[index1] + 3.212 * parameters[index2]
})

In Swift 3.2, it gets the following errors:

/Users/kevin/Desktop/TestClosures/TestClosures/TestClosures.swift:14:13: error: expression was too complex to be solved in reasonable time; consider breaking up the expression into distinct sub-expressions
let calc1 = Calculator(
            ^~~~~~~~~~~
/Users/kevin/Desktop/TestClosures/TestClosures/TestClosures.swift:25:38: error: type 'Double' has no subscript members
        -302.908 + 0.162 * parameters[index1] + 3.112 * parameters[index2] + 0.392 * parameters[index3]
                           ~~~~~~~~~~^~~~~~~~
/Users/kevin/Desktop/TestClosures/TestClosures/TestClosures.swift:39:38: error: type 'Double' has no subscript members
        -2932.32 + 1.253 * parameters[index1] + 3.212 * parameters[index2]
                           ~~~~~~~~~~^~~~~~~~

I would expect that declaring the parameters and return type in the closure would help clear things up, but it seems to have made it worse.

[swift-ci]

Comment by Kevin A. Mitchell (JIRA)

I found an interesting data point in searching for a work around.

If a mere variable assignment is involved, and an explicit return (it needs both), then it compiles:

let calc2 = Calculator(

    tCrit: 1.962,
    predictedValue: { parameters in
        let value = -302.908 + 0.162 * parameters[index1] + 3.112 * parameters[index2] + 0.392 * parameters[index3]
        return value
})

[slavapestov]

This is now fast.