Sort Slice Non Slice

ID

go.sort_slice_non_slice

Severity

high

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Reliability

Language

Go

Tags

reliability, suspicious

Description

Reports a sort.Slice or sort.SliceStable call whose first argument is a fixed-size array rather than a slice. These functions reflect on their argument and panic at runtime with sort.Slice of non-slice when it is not a slice.

Rationale

In Go an array [N]T is a distinct type from a slice []T, and sort.Slice only works on slices. Passing an array is the classic mistake; the fix is to sort a slice that views the array, arr[:]. Because the resolved type system maps arrays and slices to the same kind, the check decides array-vs-slice structurally and flags only two unambiguous cases: an array composite literal, and an identifier that resolves to a variable declared with an explicit array type.

var arr [3]int = ...
sort.Slice(arr, less)        // FLAW — arr is an array, not a slice
sort.Slice([5]int{}, less)   // FLAW — array literal

sort.Slice(sl, less)         // OK — sl is a slice

Remediation

Pass a slice to sort.Slice. To sort the elements of an array, slice it first: sort.Slice(arr[:], less).

References