Support math profile extension to Unicode identifiers

https://www.unicode.org/L2/L2022/22230-math-profile.pdf

Author: jagot

sphinx/util/cfamily.py

@@ -31,12 +31,14 @@
         # make sure they are in sync.
         (~?\b[a-zA-Z_])  # ordinary identifiers
     |   \p{XID_Start}    # Unicode-allowed starting characters for identifiers
+    |   \p{ID_Compat_Math_Start}    # Unicode-allowed starting mathematical characters for identifiers
     |   (@[a-zA-Z0-9_])  # our extension for names of anonymous entities
     )
     (
         [a-zA-Z0-9_]     # ordinary identifiers
     |   \p{XID_Continue} # Unicode-allowed continuing characters for identifiers
-    )*\b
+    |   \p{ID_Compat_Math_Continue} # Unicode-allowed continuing mathematical characters for identifiers
+    )*
     """,
     flags=re.VERBOSE,
 )

tests/test_domains/test_domain_cpp.py

@@ -876,6 +876,9 @@ def test_domain_cpp_ast_function_definitions() -> None:
            2: '8ψcomputed',
            3: '8ψcomputed',
            4: '8ψcomputed'})
+    check('function', 'norm₂(V x)', {1: 'norm₂__V', 2: '5norm₂1V', 3: '5norm₂1V', 4: '5norm₂1V'})
+    check('function', '∇(V x)', {1: '∇__V', 2: '1∇1V', 3: '1∇1V', 4: '1∇1V'})
+    check('function', 'compute∂(V x)', {1: 'compute∂__V', 2: '8compute∂1V', 3: '8compute∂1V', 4: '8compute∂1V'})
 
     # TODO: make tests for functions in a template, e.g., Test<int&&()>
     # such that the id generation for function type types is correct.