[SR-7070] Compilation never seems to finish for literal array expression

[swift-ci]

Previous ID	SR-7070
Radar	None
Original Reporter	tcurdt (JIRA User)
Type	Bug

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug, Performance, TypeChecker
Assignee	@xedin
Priority	Medium

md5: 2621381c1646c125860053a4e992db17

Issue Description:

I've come across what I believe is a bug. I have code along the lines of:

func bar() -> [UInt8] {
 return [ 0x00 ]
 }
let foo: [UInt8] =
 bar() +
 bar() +
 ...
 bar()

Given that the types are very explicit I didn't think it should be too hard to figure out the type information. Yet if this list becomes longer compilation never finishes - at least not a reasonable time. I always aborted. Also because the CPU and memory usage was crazy. (40GB of RAM and counting).

Another similar example should also demonstrate the problem:

While this compiles fine

let foo: [UInt8] =
 [1] +
 [2]

this does not

let foo: [UInt8] =
 [1] +
 [2] +
 [3] +
 [4] +
 [5] +
 [6] +
 [7]

For the time being switching to

var foo: [UInt8] = []
 foo += bar()
 foo += bar()
 foo += bar()
 foo += bar()
 foo += bar()

is a really ugly workaround. If anyone has a better workaround please let me know.

I am using

$ swift -v
Apple Swift version 4.0.3 (swiftlang-900.0.74.1 clang-900.0.39.2)
Target: x86_64-apple-macosx10.9
/Applications/Xcode.app/Contents/Developer/usr/bin/lldb "--repl=-enable-objc-interop -sdk /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.13.sdk -color-diagnostics"

[belkadan]

cc @xedin