Fix eltype invalidation for SparsityPatternCSC (#304)

SparsityPatternCSC{Ti} <: AbstractMatrix{Bool} but the custom
Base.eltype method was returning Ti (the index type) instead of Bool.
This caused 24,906 method invalidations when loading the package,
as it invalidated the backedge from Base.eltype(::AbstractArray).

Change the custom method to SparseArrays.indtype instead, since
that's what the type parameter Ti actually represents. The eltype
is now correctly inherited from AbstractMatrix{Bool}.

Co-authored-by: ChrisRackauckas-Claude <accounts@chrisrackauckas.com>
Co-authored-by: Guillaume Dalle <22795598+gdalle@users.noreply.github.com>

Author: 3 people

src/graph.jl

@@ -23,7 +23,7 @@ end
 
 SparsityPatternCSC(A::SparseMatrixCSC) = SparsityPatternCSC(A.m, A.n, A.colptr, A.rowval)
 
-Base.eltype(::SparsityPatternCSC{T}) where {T} = T
+SparseArrays.indtype(::SparsityPatternCSC{T}) where {T} = T
 Base.size(S::SparsityPatternCSC) = (S.m, S.n)
 Base.size(S::SparsityPatternCSC, d::Integer) = d::Integer <= 2 ? size(S)[d] : 1
 Base.axes(S::SparsityPatternCSC, d::Integer) = Base.OneTo(size(S, d))

test/graph.jl

@@ -15,7 +15,8 @@ using Test
 ## SparsityPatternCSC
 
 @testset "SparsityPatternCSC" begin
-    @test eltype(SparsityPatternCSC(sprand(10, 10, 0.1))) == Int
+    @test eltype(SparsityPatternCSC(sprand(10, 10, 0.1))) == Bool
+    @test SparseArrays.indtype(SparsityPatternCSC(sprand(10, 10, 0.1))) == Int
     @testset "Transpose" begin
         for _ in 1:1000
             m, n = rand(100:1000), rand(100:1000)