maint: make python-flint work with Cython 3.2

Followup and proper fix after

flintlib#337

Author: oscarbenjamin

README.md

@@ -144,12 +144,16 @@ Compatible versions:
 
 | python-flint | Release date  | CPython     | FLINT      | Cython           |
 |--------------|---------------|-------------|------------|------------------|
+| `0.9.0`      |      ???      | `3.11-3.14` | `3.0-3.3`  | `3.1-3.2?`       |
 | `0.8.0`      | 29th Aug 2025 | `3.11-3.14` | `3.0-3.3`  | `3.1` only       |
 | `0.7.0`      | 16th Mar 2025 | `3.11-3.13` | `3.0-3.2`  | `3.0.11-3.1.0a1` |
 | `0.6.0`      |  1st Feb 2024 | `3.9-3.12`  | `3.0` only | `3.0` only       |
 
 The requirement for Cython 3.1 is only for CPython's free-threaded build.
-Otherwise Cython 3.0 is fine. As of python-flint 0.7.0, CPython 3.13 [PEP
+Otherwise Cython 3.0 is fine. Cython 3.2 is required for a stable ABI build of
+python-flint.
+
+As of python-flint 0.7.0, CPython 3.13 [PEP
 703](https://peps.python.org/pep-0703/) free-threaded (no-GIL) builds of
 python-flint are provided. In the the free-threaded build, mutating matrices or
 polynomials from multiple threads can lead to memory corruption. There are some

meson.build

@@ -15,7 +15,7 @@ project(
 flint_lower = '>=3.0'
 flint_upper = '<3.4'
 cython_lower = '>=3.0.11'
-cython_upper = '<3.2'
+cython_upper = '<3.3'
 
 py = import('python').find_installation(pure: false)
 dep_py = py.dependency()

pyproject.toml

@@ -41,7 +41,7 @@ content-type = "text/markdown"
 # fine. It is not possible to have a separate version constraint here for the
 # freethreading build only though.
 #
-requires = ["meson-python >= 0.18", "cython >=3.1,<3.2"]
+requires = ["meson-python >= 0.18", "cython >=3.1,<3.3"]
 build-backend = "mesonpy"
 
 [tool.meson-python]

src/flint/types/_gr.pyx

@@ -602,11 +602,11 @@ cdef class gr_ctx(flint_ctx):
     ###
     # Square Roots
 
-    def is_square(self, x):
+    def is_square(self, x) -> bool | None:
         """
         Returns whether x is a perfect square in the context.
         """
-        return self._is_square(self(x))
+        return truth_to_py(self._is_square(self(x)))
 
     def sqrt(self, x) -> gr:
         """
@@ -1912,7 +1912,7 @@ cdef class gr(flint_scalar):
         >>> Q(4).sqrt()
         2
         """
-        return truth_to_py(self.ctx.is_square(self))
+        return self.ctx.is_square(self)
 
     def sqrt(self):
         """Return the square root of the element if it exists.