fix: add! for QadicFieldElem (#1990)

Author: thofma

src/flint/qadic.jl

@@ -618,9 +618,9 @@ function mul!(z::QadicFieldElem, x::QadicFieldElem, y::QadicFieldElem)
 end
 
 function add!(z::QadicFieldElem, x::QadicFieldElem, y::QadicFieldElem)
-  z.N = min(x.N, y.N)
   ctx = parent(x)
   @ccall libflint.qadic_add(z::Ref{QadicFieldElem}, x::Ref{QadicFieldElem}, y::Ref{QadicFieldElem}, ctx::Ref{QadicField})::Nothing
+  setprecision!(z, min(x.N, y.N))
   return z
 end
 

test/flint/qadic-test.jl

@@ -116,6 +116,13 @@ end
 
   @test shift_right(a, 2) == R(7)^-2 + 2*R(7)^-1 + 4*7^0 + O(R, 7^3)
   @test shift_left(a, 2) == 7^2 + 2*7^3 + 4*7^4 + O(R, 7^5)
+
+  #
+  R, _ = QadicField(19, 1, 10)
+  x = 2*19^1 + 17*19^3 + 5*19^4 + 10*19^5 + O(R, 19^6)
+  y = 9*19^0 + 9*19^1 + 14*19^2 + 4*19^3 + 11*19^4 + O(R, 19^5)
+  @test isequal(add!(deepcopy(x), x, y), x + y)
+  @test hash(add!(deepcopy(x), x, y)) == hash(x + y)
 end
 
 @testset "QadicFieldElem.unary_ops" begin