From 9a4a751d4004114a361dae1349acef5c1ed72f06 Mon Sep 17 00:00:00 2001
From: Tommy Hofmann <thofma@gmail.com>
Date: Thu, 12 Dec 2024 16:59:35 +0100
Subject: [PATCH] fix: check argument for map of polynomial rings (#4398)

---
 src/Rings/MPolyMap/MPolyQuo.jl     |  1 +
 test/Rings/MPolyAnyMap/MPolyQuo.jl | 10 ++++++++++
 2 files changed, 11 insertions(+)

diff --git a/src/Rings/MPolyMap/MPolyQuo.jl b/src/Rings/MPolyMap/MPolyQuo.jl
index 0c1ebfc0ca54..9c4650858e86 100644
--- a/src/Rings/MPolyMap/MPolyQuo.jl
+++ b/src/Rings/MPolyMap/MPolyQuo.jl
@@ -152,6 +152,7 @@ end
 # The two main evaluation methods
 function (F::MPolyAnyMap{<: MPolyQuoRing})(g)
   if g isa elem_type(domain(F))
+    @req parent(g) === domain(F) "Element not in domain"
     if coefficient_map(F) === nothing
       return _evaluate_plain(F, g)
     else 
diff --git a/test/Rings/MPolyAnyMap/MPolyQuo.jl b/test/Rings/MPolyAnyMap/MPolyQuo.jl
index 6a7e3929552c..d8275e9afcb3 100644
--- a/test/Rings/MPolyAnyMap/MPolyQuo.jl
+++ b/test/Rings/MPolyAnyMap/MPolyQuo.jl
@@ -212,4 +212,14 @@ end
   # The test is whether the following two lines work at all
   AtoR = @inferred hom(A, R, QtoR, [ x^2, y^2, x*y ])
   @test isone(AtoR(A(1)))
+
+  let
+    Qt, (t,) = polynomial_ring(QQ, [:t])
+    QT, (T,) = polynomial_ring(QQ, [:T])
+    Q1, = quo(Qt, ideal(Qt, [t]))
+    Q2, = quo(QT, ideal(QT, [T^2]))
+    h = hom(Q2, Q1, [Qt(t)])
+    @test_throws ArgumentError h(t)
+  end
+
 end