[SR-4864] error: expression was too complex to be solved in reasonable time

[weissi]

Previous ID	SR-4864
Radar	rdar://problem/32149641
Original Reporter	@weissi
Type	Bug
Status	Resolved
Resolution	Duplicate

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug, 4.0Regression, TypeChecker
Assignee	@weissi
Priority	Medium

md5: e3dcd3e211ea39b44ad3038337af8a18

blocks:

• SR-4709 SRP source breakage: error: expression was too complex

Issue Description:

in the latest Swift 4 snapshot, this program

private extension UInt32 {
    /* this takes an UInt32 in big-endian representation and converts it to
       whatever endianness the we're running on. It does work for both big
       and little endian machines.
       Cf. https://commandcenter.blogspot.co.uk/2012/04/byte-order-fallacy.html
    */
    static func from(bigEndian input: UInt32) -> UInt32 {
        var val: UInt32 = input
        return withUnsafePointer(to: &val) { (ptr: UnsafePointer<UInt32>) -> UInt32 in
            return ptr.withMemoryRebound(to: UInt8.self, capacity: 4) { data in
                return (UInt32(data[3]) << 0) | (UInt32(data[2]) << 8) | (UInt32(data[1]) << 16) | (UInt32(data[0]) << 24)
            }
        }
    }
}

let x = UInt32.from(bigEndian: 17)
print(x)

fails to compile with

$ /Library/Developer/Toolchains/swift-4.0-DEVELOPMENT-SNAPSHOT-2017-05-09-a.xctoolchain/usr/bin/swiftc test.swift 
test.swift:9:16: error: expression was too complex to be solved in reasonable time; consider breaking up the expression into distinct sub-expressions
        return withUnsafePointer(to: &val) { (ptr: UnsafePointer<UInt32>) -> UInt32 in
               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

but is just fine in Swift 3.1 release.

[rudkx]

@swift-ci create

[moiseev]

@weissi just wondering why not the built-in endiannes conversion routines?

[moiseev]

This is essentially the same regression reported in #47286
I have a patch that makes both expressions typecheck successfully in Swift 3 mode.
Resolving this one as duplicate.