[Rule Request] Tuple Pattern Rule

[marcelofabri]

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Rule Request

1. Why should this rule be added? Share links to existing discussion about what
   the community thinks about this.

From Google's Swift Style Guide:

Assigning variables through a tuple pattern (sometimes referred to as a tuple shuffle) is only permitted if the left-hand side of the assignment is unlabeled.

Labels on the left-hand side closely resemble type annotations, and can lead to confusing code.

2. Provide several examples of what would and wouldn't trigger violations.

// ok
let (a, b) = (y: 4, x: 5.0)

// triggers
let (x: a, y: b) = (y: 4, x: 5.0)
let (x: Int, y: Double) = (y: 4, x: 5.0)

3. Should the rule be configurable, if so what parameters should be configurable?

Just severity.

4. Should the rule be opt-in or enabled by default? Why?
   See README.md for guidelines on when to mark a
   rule as opt-in.

Probably enabled by default, depends on oss-check.