Expensive projection repeated by a comparator

Rule ID: performance.comparator-projection-amplification@1.0.0. Availability below refers to source-scan at product 524fa07e.

V-PERF-07 — Expensive projection repeated by a comparator#

Expensive projection repeated by a comparator. It examines repeated work, allocation, traversal, retention, and scheduling cost.

Availability#

Not available in source-scan. There is no source-scan flag to activate this condition.

Example and action#

Illustrative pattern only. This is not a complete runnable package or a reproduced source-scan result. Helper APIs and omitted context must be supplied by the application.

let sorted = rows.sorted { key($0) < key($1) }

Confirm the operation is on a relevant path and measure with representative input. Preserve evaluation order, laziness, errors and memory behavior when changing the algorithm.

let keyed = rows.map { (key: key($0), value: $0) }
let sorted = keyed.sorted { $0.key < $1.key }.map(\.value)

Intended analysis#

Intended reasoning: Relate a repeated operation to its input size, consumption and cost assumptions. An intended cost warning needs the loop bounds and actual collection behavior; syntax alone is not a measured runtime regression. Required evidence: cost, multiplicity, collection, allocation, and lifetime facts

Assumptions and unknown#

The relevant facts must be admitted for the selected immutable build world. Unknown aliases, external effects, unsupported source forms or incomplete consumers can prevent a conclusion. Availability in this workflow is stated above; the illustration does not expand that availability.

Evidence and interpretation#

The target catalog describes the intended condition. It is not evidence of an active source-scan diagnostic.

Historical evidence at 4558458d: recovery-required (historical qualification is incomplete and needs further evidence). That evidence has not been requalified for this product revision.

How we validate checks explains the evidence boundary. Foundations separates method assumptions from implementation claims.