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Support Go 1.26 and later with Swiss maps always enabled #19088

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mattlord merged 1 commit into from
Jan 13, 2026
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Support Go 1.26 and later with Swiss maps always enabled #19088

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5 changes: 3 additions & 2 deletions go/hack/ensure_swiss_map.go
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
//go:build !goexperiment.swissmap
//go:build !goexperiment.swissmap && !go1.26
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@dbussink dbussink Dec 26, 2025

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We should flip this flag to goexperiment.swissmap .noswissmap instead of !goexperiment.swissmap which would work also still for 1.26 if the flag is entirely gone?

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@stefanb stefanb Dec 29, 2025

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Yes, that would be much cleaner, if goexperiment.noswissmap build constraint existed.

GOEXPERIMENT=noswissmap environment setting existed in Go 1.24 and 1.25 to disable swiss maps and was negated mapped to goexperiment.swissmap build constraint. Hence the confusion.

In go 1.26 GOEXPERIMENT=noswissmap is not supported anymore and there is no way to set goexperiment.swissmap build constraint either, so the only option is to check for go1.26 build constraint.


/*
Copyright (c) 2009 The Go Authors. All rights reserved.
Expand Down Expand Up @@ -32,7 +32,8 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

// This is invalid Go code, and it will fail to compile if you disable
// Swiss maps when building Vitess. Our runtime memory accounting system
// expects the map implementation in Go 1.24 to be Swiss.
// expects the map implementation in Go 1.24 and 1.25 to be Swiss.
// In Go 1.26 and later, Swiss maps are always enabled.

package hack

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