Fix offset1 for OffsetArrays

Author: chriselrod

src/ArrayInterface.jl

@@ -1166,6 +1166,8 @@ function __init__()
         @inline axes(A::OffsetArrays.OffsetArray) = Base.axes(A)
         @inline _axes(A::OffsetArrays.OffsetArray, dim::Integer) = Base.axes(A, dim)
         @inline axes(A::OffsetArrays.OffsetArray{T,N}, ::StaticInt{M}) where {T,M,N} = _axes(A, StaticInt{M}(), gt(StaticInt{M}(),StaticInt{N}()))
+        @inline known_offset1(::Type{<:OffsetArrays.OffsetArray}) = 1
+        @inline known_offset1(::Type{<:OffsetArrays.OffsetVector}) = nothing
     end
 end
 

src/stridelayout.jl

@@ -78,7 +78,7 @@ Returns the offset of the linear indices for `x`.
 @inline function offset1(x::X) where {X}
     o1 = known_offset1(X)
     if o1 === nothing
-        return firstinde(x)
+        return firstindex(x)
     else
         return static(o1)
     end

test/runtests.jl

@@ -681,7 +681,11 @@ end
     @test @inferred(ArrayInterface.offsets(Op)) === (11, 4, 8)
 
     @test @inferred(ArrayInterface.offsets((1,2,3))) === (StaticInt(1),)
-
+    @test @inferred(ArrayInterface.offset1(O)) === StaticInt(1)
+    @test @inferred(ArrayInterface.offset1(Op)) === StaticInt(1)
+    o = OffsetArray(vec(A), 8);
+    @test @inferred(ArrayInterface.offset1(o)) === 9
+  
     if VERSION ≥ v"1.6.0-DEV.1581"
         colors = [(R = rand(), G = rand(), B = rand()) for i ∈ 1:100];