sort: drop implementation for Go <1.21

Now that Go 1.22.6 is the minimum bootstrap toolchain (cf. CL 606156),
the fallback implementation for Go versions <1.21 can be dropped.

For #61180
For #64751

Change-Id: Idfeca0a6e9f490e1ab0f308ead372612402923ea
Reviewed-on: https://go-review.googlesource.com/c/go/+/607315
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Commit-Queue: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>

3 files changed, 10 insertions, 44 deletions

diff --git a/src/sort/sort.go b/src/sort/sort.go
index 6db161f0c0..042ec4a8be 100644
--- a/src/sort/sort.go
+++ b/src/sort/sort.go
@@ -7,7 +7,10 @@
 // Package sort provides primitives for sorting slices and user-defined collections.
 package sort
 
-import "math/bits"
+import (
+	"math/bits"
+	"slices"
+)
 
 // An implementation of Interface can be sorted by the routines in this package.
 // The methods refer to elements of the underlying collection by integer index.
@@ -162,34 +165,34 @@ func (x StringSlice) Sort() { Sort(x) }
 // Ints sorts a slice of ints in increasing order.
 //
 // Note: as of Go 1.22, this function simply calls [slices.Sort].
-func Ints(x []int) { intsImpl(x) }
+func Ints(x []int) { slices.Sort(x) }
 
 // Float64s sorts a slice of float64s in increasing order.
 // Not-a-number (NaN) values are ordered before other values.
 //
 // Note: as of Go 1.22, this function simply calls [slices.Sort].
-func Float64s(x []float64) { float64sImpl(x) }
+func Float64s(x []float64) { slices.Sort(x) }
 
 // Strings sorts a slice of strings in increasing order.
 //
 // Note: as of Go 1.22, this function simply calls [slices.Sort].
-func Strings(x []string) { stringsImpl(x) }
+func Strings(x []string) { slices.Sort(x) }
 
 // IntsAreSorted reports whether the slice x is sorted in increasing order.
 //
 // Note: as of Go 1.22, this function simply calls [slices.IsSorted].
-func IntsAreSorted(x []int) bool { return intsAreSortedImpl(x) }
+func IntsAreSorted(x []int) bool { return slices.IsSorted(x) }
 
 // Float64sAreSorted reports whether the slice x is sorted in increasing order,
 // with not-a-number (NaN) values before any other values.
 //
 // Note: as of Go 1.22, this function simply calls [slices.IsSorted].
-func Float64sAreSorted(x []float64) bool { return float64sAreSortedImpl(x) }
+func Float64sAreSorted(x []float64) bool { return slices.IsSorted(x) }
 
 // StringsAreSorted reports whether the slice x is sorted in increasing order.
 //
 // Note: as of Go 1.22, this function simply calls [slices.IsSorted].
-func StringsAreSorted(x []string) bool { return stringsAreSortedImpl(x) }
+func StringsAreSorted(x []string) bool { return slices.IsSorted(x) }
 
 // Notes on stable sorting:
 // The used algorithms are simple and provable correct on all input and use
diff --git a/src/sort/sort_impl_120.go b/src/sort/sort_impl_120.go
deleted file mode 100644
index 5980da67e7..0000000000
--- a/src/sort/sort_impl_120.go
+++ /dev/null
@@ -1,15 +0,0 @@
-// Copyright 2023 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build !go1.21
-
-package sort
-
-func intsImpl(x []int)         { Sort(IntSlice(x)) }
-func float64sImpl(x []float64) { Sort(Float64Slice(x)) }
-func stringsImpl(x []string)   { Sort(StringSlice(x)) }
-
-func intsAreSortedImpl(x []int) bool         { return IsSorted(IntSlice(x)) }
-func float64sAreSortedImpl(x []float64) bool { return IsSorted(Float64Slice(x)) }
-func stringsAreSortedImpl(x []string) bool   { return IsSorted(StringSlice(x)) }
diff --git a/src/sort/sort_impl_go121.go b/src/sort/sort_impl_go121.go
deleted file mode 100644
index 0a6a6a62e7..0000000000
--- a/src/sort/sort_impl_go121.go
+++ /dev/null
@@ -1,22 +0,0 @@
-// Copyright 2023 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build go1.21
-
-// Starting with Go 1.21, we can leverage the new generic functions from the
-// slices package to implement some `sort` functions faster. However, until
-// the bootstrap compiler uses Go 1.21 or later, we keep a fallback version
-// in sort_impl_120.go that retains the old implementation.
-
-package sort
-
-import "slices"
-
-func intsImpl(x []int)         { slices.Sort(x) }
-func float64sImpl(x []float64) { slices.Sort(x) }
-func stringsImpl(x []string)   { slices.Sort(x) }
-
-func intsAreSortedImpl(x []int) bool         { return slices.IsSorted(x) }
-func float64sAreSortedImpl(x []float64) bool { return slices.IsSorted(x) }
-func stringsAreSortedImpl(x []string) bool   { return slices.IsSorted(x) }