Add NEWS entry for adjtrans of Triangular types (JuliaLang#38398)

NEWS.md

@@ -164,6 +164,10 @@ Standard library changes
 * `(+)(::UniformScaling)` is now defined, making `+I` a valid unary operation ([#36784]).
 * Instances of `UniformScaling` are no longer `isequal` to matrices. Previous
  behaviour violated the rule that `isequal(x, y)` implies `hash(x) == hash(y)`.
+* Transposing `*Triangular` matrices now returns matrices of the opposite triangular type, consistently
+ with `adjoint!(::*Triangular)` and `transpose!(::*Triangular)`. Packages containing methods with, e.g.,
+ `Adjoint{<:Any,<:LowerTriangular{<:Any,<:OwnMatrixType}}` should replace that by
+ `UpperTriangular{<:Any,<:Adjoint{<:Any,<:OwnMatrixType}}` in the method signature ([#38168]).
 
 #### Markdown
 

stdlib/LinearAlgebra/src/triangular.jl

@@ -402,16 +402,6 @@ transpose(A::UpperTriangular) = LowerTriangular(transpose(A.data))
 transpose(A::UnitLowerTriangular) = UnitUpperTriangular(transpose(A.data))
 transpose(A::UnitUpperTriangular) = UnitLowerTriangular(transpose(A.data))
 
-# legacy copy methods (not sure if we may delete them, these are no longer required)
-# Base.copy(A::Adjoint{<:Any,<:LowerTriangular}) = adjoint!(copy(A.parent))
-# Base.copy(A::Adjoint{<:Any,<:UpperTriangular}) = adjoint!(copy(A.parent))
-# Base.copy(A::Adjoint{<:Any,<:UnitLowerTriangular}) = adjoint!(copy(A.parent))
-# Base.copy(A::Adjoint{<:Any,<:UnitUpperTriangular}) = adjoint!(copy(A.parent))
-# Base.copy(A::Transpose{<:Any,<:LowerTriangular}) = transpose!(copy(A.parent))
-# Base.copy(A::Transpose{<:Any,<:UpperTriangular}) = transpose!(copy(A.parent))
-# Base.copy(A::Transpose{<:Any,<:UnitLowerTriangular}) = transpose!(copy(A.parent))
-# Base.copy(A::Transpose{<:Any,<:UnitUpperTriangular}) = transpose!(copy(A.parent))
-
 transpose!(A::LowerTriangular) = UpperTriangular(copytri!(A.data, 'L', false, true))
 transpose!(A::UnitLowerTriangular) = UnitUpperTriangular(copytri!(A.data, 'L', false, true))
 transpose!(A::UpperTriangular) = LowerTriangular(copytri!(A.data, 'U', false, true))

stdlib/LinearAlgebra/test/triangular.jl

@@ -158,9 +158,11 @@ for elty1 in (Float32, Float64, BigFloat, ComplexF32, ComplexF64, Complex{BigFlo
  @test copy(viewA1') == Matrix(viewA1)'
  # transpose!
  @test transpose!(copy(A1)) == transpose(A1)
+ @test typeof(transpose!(copy(A1))).name == typeof(transpose(A1)).name
  @test transpose!(t1(view(copy(A1).data, vrange, vrange))) == transpose(viewA1)
  # adjoint!
  @test adjoint!(copy(A1)) == adjoint(A1)
+ @test typeof(adjoint!(copy(A1))).name == typeof(adjoint(A1)).name
  @test adjoint!(t1(view(copy(A1).data, vrange, vrange))) == adjoint(viewA1)
  end