Disallow @cfunc being applied to a @ufunc.

Closes https://github.com/cython/cython/issues/5399

5 files changed, 16 insertions, 4 deletions

diff --git a/Cython/Compiler/ParseTreeTransforms.py b/Cython/Compiler/ParseTreeTransforms.py
index 6c4275dbd..987142f37 100644
--- a/Cython/Compiler/ParseTreeTransforms.py
+++ b/Cython/Compiler/ParseTreeTransforms.py
@@ -1315,6 +1315,8 @@ class InterpretCompilerDirectives(CythonTransform):
         directives = []
         realdecs = []
         both = []
+        current_opt_dict = dict(self.directives)
+        missing = object()
         # Decorators coming first take precedence.
         for dec in node.decorators[::-1]:
             new_directives = self.try_to_parse_directives(dec.decorator)
@@ -1322,8 +1324,11 @@ class InterpretCompilerDirectives(CythonTransform):
                 for directive in new_directives:
                     if self.check_directive_scope(node.pos, directive[0], scope_name):
                         name, value = directive
-                        if self.directives.get(name, object()) != value:
+                        if current_opt_dict.get(name, missing) != value:
+                            if name == 'cfunc' and 'ufunc' in current_opt_dict:
+                                error(dec.pos, "Cannot apply @cfunc to @ufunc, please reverse the decorators.")
                             directives.append(directive)
+                            current_opt_dict[name] = value
                         if directive[0] == 'staticmethod':
                             both.append(dec)
                     # Adapt scope type based on decorators that change it.
diff --git a/docs/examples/userguide/numpy_ufuncs/ufunc.py b/docs/examples/userguide/numpy_ufuncs/ufunc.py
index adbb49e8d..874183c84 100644
--- a/docs/examples/userguide/numpy_ufuncs/ufunc.py
+++ b/docs/examples/userguide/numpy_ufuncs/ufunc.py
@@ -1,8 +1,8 @@
 # tag: numpy
 import cython
 
-@cython.cfunc
 @cython.ufunc
+@cython.cfunc
 def add_one(x: cython.double) -> cython.double:
     # of course, this simple operation can already by done efficiently in Numpy!
     return x+1
diff --git a/docs/examples/userguide/numpy_ufuncs/ufunc_ctuple.py b/docs/examples/userguide/numpy_ufuncs/ufunc_ctuple.py
index 1bae902f9..b3f4fb6de 100644
--- a/docs/examples/userguide/numpy_ufuncs/ufunc_ctuple.py
+++ b/docs/examples/userguide/numpy_ufuncs/ufunc_ctuple.py
@@ -1,7 +1,7 @@
 # tag: numpy
 import cython
 
-@cython.cfunc
 @cython.ufunc
+@cython.cfunc
 def add_one_add_two(x: cython.int) -> tuple[cython.int, cython.int]:
     return x+1, x+2
diff --git a/docs/examples/userguide/numpy_ufuncs/ufunc_fused.py b/docs/examples/userguide/numpy_ufuncs/ufunc_fused.py
index dd01a508e..01cc3bc57 100644
--- a/docs/examples/userguide/numpy_ufuncs/ufunc_fused.py
+++ b/docs/examples/userguide/numpy_ufuncs/ufunc_fused.py
@@ -1,7 +1,7 @@
 # tag: numpy
 import cython
 
-@cython.cfunc
 @cython.ufunc
+@cython.cfunc
 def generic_add_one(x: cython.numeric) -> cython.numeric:
     return x+1
diff --git a/tests/errors/pure_errors.py b/tests/errors/pure_errors.py
index a480d7abe..75682a5a1 100644
--- a/tests/errors/pure_errors.py
+++ b/tests/errors/pure_errors.py
@@ -68,6 +68,12 @@ def test_contradicting_decorators2(x: object) -> object:
     return x
 
 
+@cython.cfunc
+@cython.ufunc
+def add_one(x: cython.double) -> cython.double:
+    return x+1
+
+
 _ERRORS = """
 44:22: Calling gil-requiring function not allowed without gil
 45:24: Calling gil-requiring function not allowed without gil
@@ -75,6 +81,7 @@ _ERRORS = """
 53:0: Exception clause not allowed for function returning Python object
 59:0: cfunc and ccall directives cannot be combined
 65:0: cfunc and ccall directives cannot be combined
+71:0: Cannot apply @cfunc to @ufunc, please reverse the decorators.
 """
 
 _WARNINGS = """