[SR-10161] compiler is unable to type-check this expression in reasonable time

[an0]

Previous ID	SR-10161
Radar	None
Original Reporter	@an0
Type	Bug

Additional Detail from JIRA

Votes	1
Component/s	Compiler
Labels	Bug, 5.0Regression, TypeChecker
Assignee	None
Priority	Medium

md5: b4414020ec7c32c7070fbbbb2ababd19

Issue Description:

This is a regression in Swift 5. It compiles fine with Swift 4.2.1.

let a = 0
let b = 0
let c = 0
// error: the compiler is unable to type-check this expression in reasonable time; try breaking up the expression into distinct sub-expressions
[(-b + c) / (2 * a), (-b - c) / (2 * a)]

[belkadan]

cc @xedin

[NevinBR]

Would it be feasible to introduce a rule to prefer same-type operators?

Something along the lines of:

“For all operators in an expression which have at least one candidate with lhs and rhs the same type, first try to find a valid solution using only those same-type candidates. If a solution is found, then stop and do not try mixed-type operators.”

[slavapestov]

This was fixed a while ago, it's fast in Swift 6.1.