force sym/herm back to return Matrix (1.6 inference fix) (#393)

* force sym/herm back to return Matrix

* =bump version

Author: oxinabox

Project.toml

@@ -1,6 +1,6 @@
 name = "ChainRules"
 uuid = "082447d4-558c-5d27-93f4-14fc19e9eca2"
-version = "0.7.55"
+version = "0.7.56"
 
 [deps]
 ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"

src/rulesets/LinearAlgebra/symmetric.jl

@@ -68,7 +68,7 @@ end
         end
     end
     L, U, D = LowerTriangular(ΔΩ), UpperTriangular(ΔΩ), Diagonal(ΔΩ)
-    return uplo === :U ? U .+ transpose(L) - D : L .+ transpose(U) - D
+    return Matrix(uplo === :U ? U .+ transpose(L) - D : L .+ transpose(U) - D)
 end
 
 @inline function _hermitian_back(ΔΩ, uplo::Symbol)
@@ -83,7 +83,7 @@ end
         end
     end
     L, U, rD = LowerTriangular(ΔΩ), UpperTriangular(ΔΩ), real.(Diagonal(ΔΩ))
-    return uplo === :U ? U .+ L' - rD : L .+ U' - rD
+    return Matrix(uplo === :U ? U .+ L' - rD : L .+ U' - rD)
 end
 
 #####