Details
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Type:
Bug
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Status: Open
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Priority:
Medium
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Resolution: Unresolved
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Component/s: Compiler
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Labels:
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Environment:
OSX 10.11.3 (15D21), (Swift master/f560f3caac06723, llvm stable/0d07a5d3d55078) also tested with Xcode 7.2.1
Description
I experienced an infinite loop in the compiler while working with `Range`s. I tried to checkout the current version (Swift master/f560f3caac06723, llvm stable/0d07a5d3d55078) and tried to understand more about it.
Disclaimer: It's the first time I try to go deeper in this land, I'm just trying to be a bit more helpful than just reporting the bug but I might be completely wrong 
Looks like the infinite loop happens at `CSSolver.cpp:1310`and `CSSolver.cpp:1739` where `ConstraintSystem::solveRec` is calling `ConstraintSystem::solveSimplified`that again calls `ConstraintSystem::solveRec`.
I will try to understand more but ATM I'm not experienced enough with this codebase to have proper fixes.
Looks like array of Range(s) cause the type checking to be very slow, the more you add Ranges to the array the more it slow down... 1 range okay, 2 ranges slower, .... 8 ranges VERY slow, 9 ranges infinite loop (? or just extremely slow ?).
Still investigating but looks like happening only for literal Ranges, also trying an array of ClosedInterval ranges (let c = [1...2,1...2,1...2,1...2,1...2,1...2,1...2,1...2,1...2,1...2,1...2,1...2] ) is slow but works, replacing the last entry with `1..<2` breaks it.
I'm wondering if all this is just something that should fall into *expression was too complex to be solved in reasonable time; consider breaking up the expression into distinct sub-expressions* because I actually got that result also for this kind of expression