fix int – float equality for big ints, inf and nan

Author: silmeth

tests/snippets/int_float_equality.py

@@ -0,0 +1,15 @@
+# 10**308 cannot be represented exactly in f64, thus it is not equal to 1e308 float
+assert not (10**308 == 1e308)
+# but the 1e308 float can be converted to big int and then it still should be equal to itself
+assert int(1e308) == 1e308
+
+# and the equalities should be the same when operands switch sides
+assert not (1e308 == 10**308)
+assert 1e308 == int(1e308)
+
+# floats that cannot be converted to big ints shouldn’t crash the vm
+import math
+assert not (10**500 == math.inf)
+assert not (math.inf == 10**500)
+assert not (10**500 == math.nan)
+assert not (math.nan == 10**500)

vm/src/obj/objfloat.rs

@@ -4,6 +4,7 @@ use super::super::pyobject::{
 use super::super::vm::VirtualMachine;
 use super::objint;
 use super::objtype;
+use num_bigint::ToBigInt;
 use num_traits::ToPrimitive;
 
 fn float_repr(vm: &mut VirtualMachine, args: PyFuncArgs) -> PyResult {
@@ -71,8 +72,13 @@ fn float_eq(vm: &mut VirtualMachine, args: PyFuncArgs) -> PyResult {
         let other = get_value(other);
         zelf == other
     } else if objtype::isinstance(other, &vm.ctx.int_type()) {
-        let other = objint::get_value(other).to_f64().unwrap();
-        zelf == other
+        let other_int = objint::get_value(other);
+
+        if let (Some(zelf_int), Some(other_float)) = (zelf.to_bigint(), other_int.to_f64()) {
+            zelf == other_float && zelf_int == other_int
+        } else {
+            false
+        }
     } else {
         false
     };

vm/src/obj/objint.rs

@@ -110,14 +110,19 @@ fn int_eq(vm: &mut VirtualMachine, args: PyFuncArgs) -> PyResult {
         args,
         required = [(zelf, Some(vm.ctx.int_type())), (other, None)]
     );
+
+    let zelf = BigInt::from_pyobj(zelf);
     let result = if objtype::isinstance(other, &vm.ctx.int_type()) {
-        let zelf = BigInt::from_pyobj(zelf);
         let other = BigInt::from_pyobj(other);
         zelf == other
     } else if objtype::isinstance(other, &vm.ctx.float_type()) {
-        let zelf = BigInt::from_pyobj(zelf).to_f64().unwrap();
-        let other = objfloat::get_value(other);
-        zelf == other
+        let other_float = objfloat::get_value(other);
+
+        if let (Some(zelf_float), Some(other_int)) = (zelf.to_f64(), other_float.to_bigint()) {
+            zelf_float == other_float && zelf == other_int
+        } else {
+            false
+        }
     } else {
         false
     };