Revert "Add new method Concat (#376)" (#479)

This reverts commit 940ded8.

README.md

@@ -113,7 +113,6 @@ Supported helpers for slices:
 - [CountValuesBy](#countvaluesby)
 - [Subset](#subset)
 - [Slice](#slice)
-- [Concat](#concat)
 - [Replace](#replace)
 - [ReplaceAll](#replaceall)
 - [Compact](#compact)
@@ -907,21 +906,6 @@ slice := lo.Slice(in, 4, 3)
 
 [[play](https://go.dev/play/p/8XWYhfMMA1h)]
 
-### Concat
-
-Returns a new slice containing all the elements in collections. Concat conserves the order of the elements.
-
-```go
-slice := lo.Concat([]int{1, 2}, []int{3, 4})
-// []int{1, 2, 3, 4}
-
-slice := lo.Concat(nil, []int{1, 2}, nil, []int{3, 4}, nil)
-// []int{1, 2, 3, 4}
-
-slice := lo.Concat[int]()
-// []int{}
-```
-
 ### Replace
 
 Returns a copy of the slice with the first n non-overlapping instances of old replaced by new.

slice.go

@@ -562,23 +562,6 @@ func Slice[T any](collection []T, start int, end int) []T {
 	return collection[start:end]
 }
 
-// Concat returns a new slice containing all the elements in
-// collections. Concat conserves the order of the elements.
-func Concat[T any](collections ...[]T) []T {
-	size := 0
-	for i := range collections {
-		size += len(collections[i])
-	}
-
-	result := make([]T, 0, size) // preallocate memory for the output slice
-	for i := 0; i < len(collections); i++ {
-		// `result` memory address is not expected to change, because we preallocated enough memory
-		result = append(result, collections[i]...)
-	}
-
-	return result
-}
-
 // Replace returns a copy of the slice with the first n non-overlapping instances of old replaced by new.
 // Play: https://go.dev/play/p/XfPzmf9gql6
 func Replace[T comparable](collection []T, old T, new T, n int) []T {

slice_test.go

@@ -689,16 +689,6 @@ func TestSlice(t *testing.T) {
 	is.Equal([]int{0, 1, 2, 3, 4}, out18)
 }
 
-func TestConcat(t *testing.T) {
-	t.Parallel()
-	is := assert.New(t)
-
-	is.Equal([]int{1, 2, 3, 4}, Concat([]int{1, 2}, []int{3, 4}))
-	is.Equal([]int{1, 2, 3, 4}, Concat(nil, []int{1, 2}, nil, []int{3, 4}, nil))
-	is.Equal([]int{}, Concat[int](nil, nil))
-	is.Equal([]int{}, Concat[int]())
-}
-
 func TestReplace(t *testing.T) {
 	t.Parallel()
 	is := assert.New(t)