Improve comparison-or-equality-test-with-negative-zero.ql

Tested query with Variant Analysis and had multiple results.

Author: Marcono1234

codeql-custom-queries-java/not-tested-queries/comparison-or-equality-test-with-negative-zero.ql

@@ -0,0 +1,49 @@
+/**
+ * Finds comparison expressions and equality tests for which one operand is
+ * a positive or negative 0 floating point literal, i.e. `-0.0f` or `+0.0d`.
+ * These comparison expressions do not differentiate between negative and
+ * positive 0 and therefore a 0 without any explicit sign should be preferred
+ * to not irritate the reader. For example:
+ * ```java
+ * boolean isZero = d == +0.0 || d == -0.0;
+ * 
+ * // Is the same as
+ * boolean isZero = d == 0.0;
+ * ```
+ * 
+ * Use the static `compare` method or the `equals` method of the wrapper class
+ * (e.g. `java.lang.Float`) methods to differentiate between those two types of 0.
+ *
+ * See also [JLS 17 §4.2.3. Floating-Point Types and Values](https://docs.oracle.com/javase/specs/jls/se17/html/jls-4.html#jls-4.2.3).
+ * 
+ * @kind problem
+ */
+
+import java
+import lib.Literals
+
+class ZeroFloatingPointLiteral extends FloatingPointLiteral_ {
+    ZeroFloatingPointLiteral() {
+        getValue().toFloat() = 0
+    }
+}
+
+class SignedZero extends UnaryExpr {
+    SignedZero() {
+        (this instanceof MinusExpr or this instanceof PlusExpr)
+        and getExpr() instanceof ZeroFloatingPointLiteral
+    }
+}
+
+from BinaryExpr expr
+where
+    (
+        expr instanceof ComparisonExpr
+        or expr instanceof EqualityTest
+    )
+    and (
+        expr.getAnOperand() instanceof SignedZero
+        // Or reading variable whose constant value is -0.0 or +0.0
+        or expr.getAnOperand().(CompileTimeConstantExpr).(RValue).getVariable().getInitializer() instanceof SignedZero
+    )
+select expr, "Comparison with -0.0 is same as comparison with +0.0"