add issuccess for CholeskyPivoted (JuliaLang#36002)

* add issuccess for CholeskyPivoted

* add tests, NEWS and compat

Author: palday

NEWS.md

@@ -47,7 +47,7 @@ Standard library changes
 * All `AbstractUnitRange{<:Integer}`s now work with `SubString`, `view`, `@view` and `@views` on strings ([#35879]).
 
 #### LinearAlgebra
-
+* New method `LinearAlgebra.issuccess(::CholeskyPivoted)` for checking whether pivoted Cholesky factorization was successful ([#36002]).
 
 #### Markdown
 

stdlib/LinearAlgebra/src/cholesky.jl

@@ -447,7 +447,7 @@ end
 Base.propertynames(F::CholeskyPivoted, private::Bool=false) =
     (:U, :L, :p, :P, (private ? fieldnames(typeof(F)) : ())...)
 
-issuccess(C::Cholesky) = C.info == 0
+issuccess(C::Union{Cholesky,CholeskyPivoted}) = C.info == 0
 
 function show(io::IO, mime::MIME{Symbol("text/plain")}, C::Cholesky{<:Any,<:AbstractMatrix})
     if issuccess(C)

stdlib/LinearAlgebra/src/factorization.jl

@@ -25,6 +25,9 @@ checknonsingular(info) = checknonsingular(info, Val{true}())
 
 Test that a factorization of a matrix succeeded.
 
+!!! compat "Julia 1.6"
+    `issuccess(::CholeskyPivoted)` requires Julia 1.6 or later.
+
 ```jldoctest
 julia> F = cholesky([1 0; 0 1]);
 

stdlib/LinearAlgebra/test/cholesky.jl

@@ -266,6 +266,8 @@ end
         @test_throws RankDeficientException cholesky!(copy(M), Val(true))
         @test_throws RankDeficientException cholesky(M, Val(true); check = true)
         @test_throws RankDeficientException cholesky!(copy(M), Val(true); check = true)
+        @test !LinearAlgebra.issuccess(cholesky(M, Val(true); check = false))
+        @test !LinearAlgebra.issuccess(cholesky!(copy(M), Val(true); check = false))
         C = cholesky(M, Val(true); check = false)
         @test_throws RankDeficientException chkfullrank(C)
         C = cholesky!(copy(M), Val(true); check = false)