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maps: handle copy with nil maps #73477

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afiune wants to merge 1 commit into from
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maps: handle copy with nil maps #73477

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3 changes: 3 additions & 0 deletions src/maps/maps.go
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Original file line number Diff line number Diff line change
Expand Up @@ -60,6 +60,9 @@ func Clone[M ~map[K]V, K comparable, V any](m M) M {
// the value in dst will be overwritten by the value associated
// with the key in src.
func Copy[M1 ~map[K]V, M2 ~map[K]V, K comparable, V any](dst M1, src M2) {
if dst == nil {
dst = make(map[K]V)
}
for k, v := range src {
dst[k] = v
}
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9 changes: 9 additions & 0 deletions src/maps/maps_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -121,6 +121,15 @@ func TestCopy(t *testing.T) {
Copy(make(M1), make(M2))
}

func TestCopyNil(t *testing.T) {
var mnil map[string]int
mc := Copy(mnil, m1)
want := m1
if !Equal(mc, want) {
t.Errorf("Copy result = %v, want %v", mc, want)
}
}

func TestDeleteFunc(t *testing.T) {
mc := Clone(m1)
DeleteFunc(mc, func(int, int) bool { return false })
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