Work around invalidation and minor LinearIndices simplifications

Author: mbauman

base/abstractarray.jl

@@ -159,7 +159,7 @@ julia> lastindex(rand(3,4,5), 2)
 4
 ```
 """
-lastindex(a::AbstractArray) = (@_inline_meta; last(eachindex(IndexLinear(), a)))
+lastindex(a::AbstractArray) = (@_inline_meta; last(LinearIndices(a)))
 lastindex(a::AbstractArray, d) = (@_inline_meta; last(axes(a, d)))
 
 """
@@ -177,7 +177,7 @@ julia> firstindex(rand(3,4,5), 2)
 1
 ```
 """
-firstindex(a::AbstractArray) = (@_inline_meta; first(eachindex(IndexLinear(), a)))
+firstindex(a::AbstractArray) = (@_inline_meta; first(LinearIndices(a)))
 firstindex(a::AbstractArray, d) = (@_inline_meta; first(axes(a, d)))
 
 first(a::AbstractArray) = a[first(eachindex(a))]

base/indices.jl

@@ -354,10 +354,11 @@ LinearIndices(inds::NTuple{N,Union{<:Integer,AbstractUnitRange{<:Integer}}}) whe
 LinearIndices(A::Union{AbstractArray,SimpleVector}) = LinearIndices(axes(A))
 
 # AbstractArray implementation
-IndexStyle(::Type{LinearIndices{N,R}}) where {N,R} = IndexLinear()
-axes(iter::LinearIndices{N,R}) where {N,R} = iter.indices
-size(iter::LinearIndices{N,R}) where {N,R} = length.(iter.indices)
-function getindex(iter::LinearIndices{N,R}, i::Int) where {N,R}
+IndexStyle(::Type{<:LinearIndices}) = IndexLinear()
+axes(iter::LinearIndices) = iter.indices
+size(iter::LinearIndices) = map(unsafe_length, iter.indices)
+length(iter::LinearIndices) = prod(size(iter))
+function getindex(iter::LinearIndices, i::Int)
     @boundscheck checkbounds(iter, i)
     i
 end