Complex addition/subtraction is not commutative

[skirpichev]

Python 3.12.8 (Thu Oct 09 17:26:36 UTC 2025)
[Graal, Oracle GraalVM, Java 25.0.1 (amd64)] on linux
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>>> x = 0; y = complex(0.0,-0.0)
>>> y+x
-0j
>>> x+y
0j

It seems, this happens because specialization exists for complex+int (and complex+float) case, but not for int+complex:

graalpython/graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/complex/ComplexBuiltins.java

Lines 960 to 971 in b12073b

	abstract static class AddNode extends BinaryOpBuiltinNode {
	@Specialization
	static PComplex doInt(PComplex left, int right,
	@Bind PythonLanguage language) {
	return PFactory.createComplex(language, left.getReal() + right, left.getImag());
	}
	@Specialization
	static PComplex doDouble(PComplex left, double right,
	@Bind PythonLanguage language) {
	return PFactory.createComplex(language, left.getReal() + right, left.getImag());
	}

Same for subtraction:

graalpython/graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/complex/ComplexBuiltins.java

Line 1077 in b12073b

abstract static class SubNode extends BinaryOpBuiltinNode {

N.B.: CPython before v3.14 had no special arithmetic rules for mixed-type operands (real values silently converted to complex type with a zero imaginary part).