Deprecate adding integers to CartesianIndex (#26284)

fixes #26227

Author: mbauman

NEWS.md

@@ -587,6 +587,9 @@ Library improvements
     collection `A`. There are also two other methods with a different API, and
     a mutating variant, `replace!` ([#22324]).
 
+  * Adding integers to `CartesianIndex` objects is now deprecated. Instead of
+    `i::Int + x::CartesianIndex`, use `i*one(x) + x` ([#26284]).
+
   * `CartesianRange` changes ([#24715]):
     - Inherits from `AbstractArray`, and linear indexing can be used to provide
       linear-to-cartesian conversion ([#24715])

base/deprecated.jl

@@ -1422,6 +1422,12 @@ end
 @deprecate reprmime(mime, x) repr(mime, x)
 @deprecate mimewritable(mime, x) showable(mime, x)
 
+# PR #26284
+@deprecate (+)(i::Integer, index::CartesianIndex) (i*one(index) + index)
+@deprecate (+)(index::CartesianIndex, i::Integer) (index + i*one(index))
+@deprecate (-)(i::Integer, index::CartesianIndex) (i*one(index) - index)
+@deprecate (-)(index::CartesianIndex, i::Integer) (index - i*one(index))
+
 # PR #23332
 @deprecate ^(x, p::Integer) Base.power_by_squaring(x,p)
 

base/multidimensional.jl

@@ -112,10 +112,6 @@ module IteratorsMD
     @inline max(index1::CartesianIndex{N}, index2::CartesianIndex{N}) where {N} =
         CartesianIndex{N}(map(max, index1.I, index2.I))
 
-    @inline (+)(i::Integer, index::CartesianIndex) = index+i
-    @inline (+)(index::CartesianIndex{N}, i::Integer) where {N} = CartesianIndex{N}(map(x->x+i, index.I))
-    @inline (-)(index::CartesianIndex{N}, i::Integer) where {N} = CartesianIndex{N}(map(x->x-i, index.I))
-    @inline (-)(i::Integer, index::CartesianIndex{N}) where {N} = CartesianIndex{N}(map(x->i-x, index.I))
     @inline (*)(a::Integer, index::CartesianIndex{N}) where {N} = CartesianIndex{N}(map(x->a*x, index.I))
     @inline (*)(index::CartesianIndex, a::Integer) = *(a,index)
 
@@ -279,7 +275,7 @@ module IteratorsMD
     @inline function start(iter::CartesianIndices)
         iterfirst, iterlast = first(iter), last(iter)
         if any(map(>, iterfirst.I, iterlast.I))
-            return iterlast+1
+            return iterlast+one(iterlast)
         end
         iterfirst
     end

test/arrayops.jl

@@ -1616,8 +1616,8 @@ end
     @test I2 + I1 == CartesianIndex((1,8,2))
     @test I1 - I2 == CartesianIndex((3,-2,-2))
     @test I2 - I1 == CartesianIndex((-3,2,2))
-    @test I1 + 1 == CartesianIndex((3,4,1))
-    @test I1 - 2 == CartesianIndex((0,1,-2))
+    @test I1 + 1*one(I1) == CartesianIndex((3,4,1))
+    @test I1 - 2*one(I1) == CartesianIndex((0,1,-2))
 
     @test zero(CartesianIndex{2}) == CartesianIndex((0,0))
     @test zero(CartesianIndex((2,3))) == CartesianIndex((0,0))