With Go 1.21, use clear in set.Clear()

This addresses the edge cases where a set couldn't be fully cleared,
and will be more efficient in cases where the loop isn't optimised
away.

To allow this to be tested in CI, configure tests with Go 1.20 and
1.21 (since 1.21 has been released, 1.19 has reached EOL).

Signed-off-by: Stephen Kitt <skitt@redhat.com>

.github/workflows/test.yml

@@ -4,7 +4,7 @@ jobs:
   build:
     strategy:
       matrix:
-        go-version: [1.19.x, 1.20.x]
+        go-version: [1.20.x, 1.21.x]
         platform: [windows-latest]
     runs-on: ${{ matrix.platform }}
     steps:
@@ -24,7 +24,7 @@ jobs:
   test:
     strategy:
       matrix:
-        go-version: [1.19.x, 1.20.x]
+        go-version: [1.20.x, 1.21.x]
         platform: [ubuntu-latest, macos-latest]
     runs-on: ${{ matrix.platform }}
     steps:
@@ -56,7 +56,7 @@ jobs:
       - name: Install Go
         uses: actions/setup-go@v3
         with:
-          go-version: 1.20.x
+          go-version: 1.21.x
       - name: Add GOBIN to PATH
         run: echo "$(go env GOPATH)/bin" >> $GITHUB_PATH
       - name: Install dependencies

set/set.go

@@ -213,17 +213,3 @@ func (s Set[T]) Clone() Set[T] {
 func (s Set[T]) SymmetricDifference(s2 Set[T]) Set[T] {
 	return s.Difference(s2).Union(s2.Difference(s))
 }
-
-// Clear empties the set.
-// It is preferable to replace the set with a newly constructed set,
-// but not all callers can do that (when there are other references to the map).
-// In some cases the set *won't* be fully cleared, e.g. a Set[float32] containing NaN
-// can't be cleared because NaN can't be removed.
-// For sets containing items of a type that is reflexive for ==,
-// this is optimized to a single call to runtime.mapclear().
-func (s Set[T]) Clear() Set[T] {
-	for key := range s {
-		delete(s, key)
-	}
-	return s
-}

set/set_go_1.20.go

@@ -0,0 +1,33 @@
+//go:build !go1.21
+
+/*
+Copyright 2023 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package set
+
+// Clear empties the set.
+// It is preferable to replace the set with a newly constructed set,
+// but not all callers can do that (when there are other references to the map).
+// In some cases the set *won't* be fully cleared, e.g. a Set[float32] containing NaN
+// can't be cleared because NaN can't be removed.
+// For sets containing items of a type that is reflexive for ==,
+// this is optimized to a single call to runtime.mapclear().
+func (s Set[T]) Clear() Set[T] {
+	for key := range s {
+		delete(s, key)
+	}
+	return s
+}

set/set_go_1.21.go

@@ -0,0 +1,27 @@
+//go:build go1.21
+
+/*
+Copyright 2023 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package set
+
+// Clear empties the set.
+// It is preferable to replace the set with a newly constructed set,
+// but not all callers can do that (when there are other references to the map).
+func (s Set[T]) Clear() Set[T] {
+	clear(s)
+	return s
+}