Do not panic when tan of a decimal number overflows

CHANGELOG.md

@@ -12,6 +12,7 @@ Bug fixes
 * `AST::clone_functions_only_filtered` now applies its filter, as does `AST::merge_filtered` when the first `AST` has no functions. Previously every function was kept (thanks [`@ImTheSquid`](https://github.com/ImTheSquid) [`#1192`](https://github.com/rhaiscript/rhai/pull/1192)).
 * `sleep` no longer panics when called with a float number that is too large (thanks [`@Rockyrok77`](https://github.com/Rockyrok77) [`#1205`](https://github.com/rhaiscript/rhai/pull/1205)).
 * Fixes string indexing bug with a single-character inclusive range (e.g. `s[1..=1]`) returning an empty string (thanks [`@youdie006`](https://github.com/youdie006) [`#1204`](https://github.com/rhaiscript/rhai/pull/1204)).
+* `tan` no longer panics on a decimal number when the result overflows - e.g. `tan(π/2)` (thanks [`@Rockyrok77`](https://github.com/Rockyrok77) [`#1203`](https://github.com/rhaiscript/rhai/pull/1203)).
 
 Enhancements
 ------------

src/packages/math_basic.rs

@@ -385,8 +385,10 @@ mod decimal_functions {
         x.cos()
     }
     /// Return the tangent of the decimal number in radians.
-    pub fn tan(x: Decimal) -> Decimal {
-        x.tan()
+    #[rhai_fn(return_raw)]
+    pub fn tan(x: Decimal) -> RhaiResultOf<Decimal> {
+        x.checked_tan()
+            .ok_or_else(|| make_err(format!("Error taking the tangent of {x}")))
     }
     /// Return the square root of the decimal number.
     #[rhai_fn(return_raw)]

tests/math.rs

@@ -1,4 +1,4 @@
 use rhai::{Engine, EvalAltResult, INT};
 
 #[cfg(not(feature = "no_float"))]
 use rhai::FLOAT;
@@ -57,3 +57,27 @@
     assert_eq!(engine.eval::<INT>(r#"parse_int("42", 16)"#).unwrap(), 0x42);
     assert_eq!(engine.eval::<INT>(r#"parse_int("abcdef", 16)"#).unwrap(), 0xabcdef);
 }
+
+#[cfg(feature = "decimal")]
+#[test]
+fn test_math_decimal_tan() {
+    use rust_decimal::Decimal;
+
+    let engine = Engine::new();
+
+    assert_eq!(engine.eval::<Decimal>(r#"parse_decimal("0").tan()"#).unwrap(), Decimal::ZERO);
+
+    // tan(π/2) and tan(3π/2) are infinite, which a Decimal cannot represent
+    assert!(matches!(
+        *engine
+            .eval::<Decimal>(r#"parse_decimal("1.5707963267948966192313216916").tan()"#)
+            .expect_err("expects tangent overflow"),
+        EvalAltResult::ErrorArithmetic(..)
+    ));
+    assert!(matches!(
+        *engine
+            .eval::<Decimal>(r#"parse_decimal("4.7123889803846898576939650749").tan()"#)
+            .expect_err("expects tangent overflow"),
+        EvalAltResult::ErrorArithmetic(..)
+    ));
+}