Some more type safety. (0.8.0)

examples/type_safety.fun

@@ -0,0 +1,72 @@
+#!/usr/bin/env fun
+
+/**
+ * This file is part of the Fun programming language.
+ * https://hanez.org/project/fun/
+ *
+ * Copyright 2025 Johannes Findeisen <you@hanez.org>
+ * Licensed under the terms of the ISC license.
+ * https://opensource.org/license/isc-license-txt
+ */
+
+// Type Safety demonstration in Fun
+
+print("== Dynamic variable (untyped) ==")
+x = 100
+print(typeof(x))   // -> "Number"
+print(x)          // -> 100
+
+x = "hello"
+print(typeof(x))   // -> "String"
+print(x)          // -> "hello"
+
+print("")
+print("== Typed variables remain type-stable ==")
+
+// Strings must always be strings
+string s = "hello"
+print(typeof(s))   // -> "String"
+print(s)           // -> "hello"
+// s = 42          // Uncomment to see runtime TypeError: expected String
+
+// Booleans are Numbers constrained to 0 or 1 (clamped)
+boolean flag = 0
+print(typeof(flag)) // -> "Number"
+print(flag)         // -> 0
+
+flag = 2            // will be clamped to 1
+print(flag)         // -> 1
+// flag = "no"      // Uncomment to see runtime TypeError: expected Number for boolean
+
+// number is a signed 64-bit integer and must remain Number
+number n = 123
+print(typeof(n))    // -> "Number"
+n = 456
+print(n)            // -> 456
+// n = "oops"       // Uncomment to see runtime TypeError: expected Number
+
+print("")
+print("== Integer width clamping ==")
+
+// Signed 8-bit: range [-128..127]
+int8 si = 130       // clamps to 127
+print(si)           // -> 127
+si = -200           // clamps to -128
+print(si)           // -> -128
+
+// Unsigned 8-bit: range [0..255]
+uint8 u = 255
+print(u)            // -> 255
+u = 300             // clamps to 255
+print(u)            // -> 255
+// u = "bad"        // Uncomment to see runtime TypeError: expected Number
+
+print("")
+print("== Nil-typed variables must stay Nil ==")
+
+nil nn = nil
+print(typeof(nn))   // -> "Nil"
+// nn = 0           // Uncomment to see runtime TypeError: expected Nil
+
+print("")
+print("Done. Uncomment lines above to see type errors in action.")